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  1. <!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">

  2. <html>

  3. <!-- This file documents the GNU linker LD

  4. (GNU Arm Embedded Toolchain 10-2020-q4-major)

  5. version 2.35.1.

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  18. <title>Options (LD)</title>

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  60. </head>

  61. 

  62. <body lang="en">

  63. <a name="Options"></a>

  64. <div class="header">

  65. <p>

  66. Next: <a href="Environment.html#Environment" accesskey="n" rel="next">Environment</a>, Up: <a href="Invocation.html#Invocation" accesskey="u" rel="up">Invocation</a> &nbsp; [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="LD-Index.html#LD-Index" title="Index" rel="index">Index</a>]</p>

  67. </div>

  68. <hr>

  69. <a name="Command_002dline-Options"></a>

  70. <h3 class="section">2.1 Command-line Options</h3>

  71. 

  72. <a name="index-command-line"></a>

  73. <a name="index-options"></a>

  74. 

  75. 

  76. <p>The linker supports a plethora of command-line options, but in actual

  77. practice few of them are used in any particular context.

  78. <a name="index-standard-Unix-system"></a>

  79. For instance, a frequent use of <code>ld</code> is to link standard Unix

  80. object files on a standard, supported Unix system.  On such a system, to

  81. link a file <code>hello.o</code>:

  82. </p>

  83. <div class="smallexample">

  84. <pre class="smallexample">ld -o <var>output</var> /lib/crt0.o hello.o -lc

  85. </pre></div>

  86. 

  87. <p>This tells <code>ld</code> to produce a file called <var>output</var> as the

  88. result of linking the file <code>/lib/crt0.o</code> with <code>hello.o</code> and

  89. the library <code>libc.a</code>, which will come from the standard search

  90. directories.  (See the discussion of the &lsquo;<samp>-l</samp>&rsquo; option below.)

  91. </p>

  92. <p>Some of the command-line options to <code>ld</code> may be specified at any

  93. point in the command line.  However, options which refer to files, such

  94. as &lsquo;<samp>-l</samp>&rsquo; or &lsquo;<samp>-T</samp>&rsquo;, cause the file to be read at the point at

  95. which the option appears in the command line, relative to the object

  96. files and other file options.  Repeating non-file options with a

  97. different argument will either have no further effect, or override prior

  98. occurrences (those further to the left on the command line) of that

  99. option.  Options which may be meaningfully specified more than once are

  100. noted in the descriptions below.

  101. </p>

  102. <a name="index-object-files"></a>

  103. <p>Non-option arguments are object files or archives which are to be linked

  104. together.  They may follow, precede, or be mixed in with command-line

  105. options, except that an object file argument may not be placed between

  106. an option and its argument.

  107. </p>

  108. <p>Usually the linker is invoked with at least one object file, but you can

  109. specify other forms of binary input files using &lsquo;<samp>-l</samp>&rsquo;, &lsquo;<samp>-R</samp>&rsquo;,

  110. and the script command language.  If <em>no</em> binary input files at all

  111. are specified, the linker does not produce any output, and issues the

  112. message &lsquo;<samp>No input files</samp>&rsquo;.

  113. </p>

  114. <p>If the linker cannot recognize the format of an object file, it will

  115. assume that it is a linker script.  A script specified in this way

  116. augments the main linker script used for the link (either the default

  117. linker script or the one specified by using &lsquo;<samp>-T</samp>&rsquo;).  This feature

  118. permits the linker to link against a file which appears to be an object

  119. or an archive, but actually merely defines some symbol values, or uses

  120. <code>INPUT</code> or <code>GROUP</code> to load other objects.  Specifying a

  121. script in this way merely augments the main linker script, with the

  122. extra commands placed after the main script; use the &lsquo;<samp>-T</samp>&rsquo; option

  123. to replace the default linker script entirely, but note the effect of

  124. the <code>INSERT</code> command.  See <a href="Scripts.html#Scripts">Scripts</a>.

  125. </p>

  126. <p>For options whose names are a single letter,

  127. option arguments must either follow the option letter without intervening

  128. whitespace, or be given as separate arguments immediately following the

  129. option that requires them.

  130. </p>

  131. <p>For options whose names are multiple letters, either one dash or two can

  132. precede the option name; for example, &lsquo;<samp>-trace-symbol</samp>&rsquo; and

  133. &lsquo;<samp>--trace-symbol</samp>&rsquo; are equivalent.  Note&mdash;there is one exception to

  134. this rule.  Multiple letter options that start with a lower case &rsquo;o&rsquo; can

  135. only be preceded by two dashes.  This is to reduce confusion with the

  136. &lsquo;<samp>-o</samp>&rsquo; option.  So for example &lsquo;<samp>-omagic</samp>&rsquo; sets the output file

  137. name to &lsquo;<samp>magic</samp>&rsquo; whereas &lsquo;<samp>--omagic</samp>&rsquo; sets the NMAGIC flag on the

  138. output.

  139. </p>

  140. <p>Arguments to multiple-letter options must either be separated from the

  141. option name by an equals sign, or be given as separate arguments

  142. immediately following the option that requires them.  For example,

  143. &lsquo;<samp>--trace-symbol foo</samp>&rsquo; and &lsquo;<samp>--trace-symbol=foo</samp>&rsquo; are equivalent.

  144. Unique abbreviations of the names of multiple-letter options are

  145. accepted.

  146. </p>

  147. <p>Note&mdash;if the linker is being invoked indirectly, via a compiler driver

  148. (e.g. &lsquo;<samp>gcc</samp>&rsquo;) then all the linker command-line options should be

  149. prefixed by &lsquo;<samp>-Wl,</samp>&rsquo; (or whatever is appropriate for the particular

  150. compiler driver) like this:

  151. </p>

  152. <div class="smallexample">

  153. <pre class="smallexample">  gcc -Wl,--start-group foo.o bar.o -Wl,--end-group

  154. </pre></div>

  155. 

  156. <p>This is important, because otherwise the compiler driver program may

  157. silently drop the linker options, resulting in a bad link.  Confusion

  158. may also arise when passing options that require values through a

  159. driver, as the use of a space between option and argument acts as

  160. a separator, and causes the driver to pass only the option to the linker

  161. and the argument to the compiler.  In this case, it is simplest to use

  162. the joined forms of both single- and multiple-letter options, such as:

  163. </p>

  164. <div class="smallexample">

  165. <pre class="smallexample">  gcc foo.o bar.o -Wl,-eENTRY -Wl,-Map=a.map

  166. </pre></div>

  167. 

  168. <p>Here is a table of the generic command-line switches accepted by the GNU

  169. linker:

  170. </p>

  171. <dl compact="compact">

  172. <dt><code>@<var>file</var></code></dt>

  173. <dd><p>Read command-line options from <var>file</var>.  The options read are

  174. inserted in place of the original @<var>file</var> option.  If <var>file</var>

  175. does not exist, or cannot be read, then the option will be treated

  176. literally, and not removed.  

  177. </p>

  178. <p>Options in <var>file</var> are separated by whitespace.  A whitespace

  179. character may be included in an option by surrounding the entire

  180. option in either single or double quotes.  Any character (including a

  181. backslash) may be included by prefixing the character to be included

  182. with a backslash.  The <var>file</var> may itself contain additional

  183. @<var>file</var> options; any such options will be processed recursively.

  184. </p>

  185. <a name="index-_002da-keyword"></a>

  186. </dd>

  187. <dt><code>-a <var>keyword</var></code></dt>

  188. <dd><p>This option is supported for HP/UX compatibility.  The <var>keyword</var>

  189. argument must be one of the strings &lsquo;<samp>archive</samp>&rsquo;, &lsquo;<samp>shared</samp>&rsquo;, or

  190. &lsquo;<samp>default</samp>&rsquo;.  &lsquo;<samp>-aarchive</samp>&rsquo; is functionally equivalent to

  191. &lsquo;<samp>-Bstatic</samp>&rsquo;, and the other two keywords are functionally equivalent

  192. to &lsquo;<samp>-Bdynamic</samp>&rsquo;.  This option may be used any number of times.

  193. </p>

  194. <a name="index-_002d_002daudit-AUDITLIB"></a>

  195. </dd>

  196. <dt><code>--audit <var>AUDITLIB</var></code></dt>

  197. <dd><p>Adds <var>AUDITLIB</var> to the <code>DT_AUDIT</code> entry of the dynamic section.

  198. <var>AUDITLIB</var> is not checked for existence, nor will it use the DT_SONAME

  199. specified in the library.  If specified multiple times <code>DT_AUDIT</code>

  200. will contain a colon separated list of audit interfaces to use. If the linker

  201. finds an object with an audit entry while searching for shared libraries,

  202. it will add a corresponding <code>DT_DEPAUDIT</code> entry in the output file.

  203. This option is only meaningful on ELF platforms supporting the rtld-audit

  204. interface.

  205. </p>

  206. <a name="index-binary-input-format"></a>

  207. <a name="index-_002db-format"></a>

  208. <a name="index-_002d_002dformat_003dformat"></a>

  209. <a name="index-input-format"></a>

  210. <a name="index-input-format-1"></a>

  211. </dd>

  212. <dt><code>-b <var>input-format</var></code></dt>

  213. <dt><code>--format=<var>input-format</var></code></dt>

  214. <dd><p><code>ld</code> may be configured to support more than one kind of object

  215. file.  If your <code>ld</code> is configured this way, you can use the

  216. &lsquo;<samp>-b</samp>&rsquo; option to specify the binary format for input object files

  217. that follow this option on the command line.  Even when <code>ld</code> is

  218. configured to support alternative object formats, you don&rsquo;t usually need

  219. to specify this, as <code>ld</code> should be configured to expect as a

  220. default input format the most usual format on each machine.

  221. <var>input-format</var> is a text string, the name of a particular format

  222. supported by the BFD libraries.  (You can list the available binary

  223. formats with &lsquo;<samp>objdump -i</samp>&rsquo;.)

  224. See <a href="BFD.html#BFD">BFD</a>.

  225. </p>

  226. <p>You may want to use this option if you are linking files with an unusual

  227. binary format.  You can also use &lsquo;<samp>-b</samp>&rsquo; to switch formats explicitly (when

  228. linking object files of different formats), by including

  229. &lsquo;<samp>-b <var>input-format</var></samp>&rsquo; before each group of object files in a

  230. particular format.

  231. </p>

  232. <p>The default format is taken from the environment variable

  233. <code>GNUTARGET</code>.

  234. See <a href="Environment.html#Environment">Environment</a>.

  235. You can also define the input format from a script, using the command

  236. <code>TARGET</code>;

  237. see <a href="Format-Commands.html#Format-Commands">Format Commands</a>.

  238. </p>

  239. <a name="index-_002dc-MRI_002dcmdfile"></a>

  240. <a name="index-_002d_002dmri_002dscript_003dMRI_002dcmdfile"></a>

  241. <a name="index-compatibility_002c-MRI"></a>

  242. </dd>

  243. <dt><code>-c <var>MRI-commandfile</var></code></dt>

  244. <dt><code>--mri-script=<var>MRI-commandfile</var></code></dt>

  245. <dd><p>For compatibility with linkers produced by MRI, <code>ld</code> accepts script

  246. files written in an alternate, restricted command language, described in

  247. <a href="MRI.html#MRI">MRI Compatible Script Files</a>.

  248. Introduce MRI script files with

  249. the option &lsquo;<samp>-c</samp>&rsquo;; use the &lsquo;<samp>-T</samp>&rsquo; option to run linker

  250. scripts written in the general-purpose <code>ld</code> scripting language.

  251. If <var>MRI-cmdfile</var> does not exist, <code>ld</code> looks for it in the directories

  252. specified by any &lsquo;<samp>-L</samp>&rsquo; options.

  253. </p>

  254. <a name="index-common-allocation"></a>

  255. <a name="index-_002dd"></a>

  256. <a name="index-_002ddc"></a>

  257. <a name="index-_002ddp"></a>

  258. </dd>

  259. <dt><code>-d</code></dt>

  260. <dt><code>-dc</code></dt>

  261. <dt><code>-dp</code></dt>

  262. <dd><p>These three options are equivalent; multiple forms are supported for

  263. compatibility with other linkers.  They assign space to common symbols

  264. even if a relocatable output file is specified (with &lsquo;<samp>-r</samp>&rsquo;).  The

  265. script command <code>FORCE_COMMON_ALLOCATION</code> has the same effect.

  266. See <a href="Miscellaneous-Commands.html#Miscellaneous-Commands">Miscellaneous Commands</a>.

  267. </p>

  268. <a name="index-_002d_002ddepaudit-AUDITLIB"></a>

  269. <a name="index-_002dP-AUDITLIB"></a>

  270. </dd>

  271. <dt><code>--depaudit <var>AUDITLIB</var></code></dt>

  272. <dt><code>-P <var>AUDITLIB</var></code></dt>

  273. <dd><p>Adds <var>AUDITLIB</var> to the <code>DT_DEPAUDIT</code> entry of the dynamic section.

  274. <var>AUDITLIB</var> is not checked for existence, nor will it use the DT_SONAME

  275. specified in the library.  If specified multiple times <code>DT_DEPAUDIT</code>

  276. will contain a colon separated list of audit interfaces to use.  This

  277. option is only meaningful on ELF platforms supporting the rtld-audit interface.

  278. The -P option is provided for Solaris compatibility.

  279. </p>

  280. <a name="index-_002d_002denable_002dnon_002dcontiguous_002dregions"></a>

  281. </dd>

  282. <dt><code>--enable-non-contiguous-regions</code></dt>

  283. <dd><p>This option avoids generating an error if an input section does not

  284. fit a matching output section. The linker tries to allocate the input

  285. section to subseque nt matching output sections, and generates an

  286. error only if no output section is large enough.  This is useful when

  287. several non-contiguous memory regions are available and the input

  288. section does not require a particular one.  The order in which input

  289. sections are evaluated does not change, for instance:

  290. </p>

  291. <div class="smallexample">

  292. <pre class="smallexample">  MEMORY {

  293.     MEM1 (rwx) : ORIGIN : 0x1000, LENGTH = 0x14

  294.     MEM2 (rwx) : ORIGIN : 0x1000, LENGTH = 0x40

  295.     MEM3 (rwx) : ORIGIN : 0x2000, LENGTH = 0x40

  296.   }

  297.   SECTIONS {

  298.     mem1 : { *(.data.*); } &gt; MEM1

  299.     mem2 : { *(.data.*); } &gt; MEM2

  300.     mem3 : { *(.data.*); } &gt; MEM2

  301.   }

  302. 

  303.   with input sections:

  304.   .data.1: size 8

  305.   .data.2: size 0x10

  306.   .data.3: size 4

  307. 

  308.   results in .data.1 affected to mem1, and .data.2 and .data.3

  309.   affected to mem2, even though .data.3 would fit in mem3.

  310. </pre></div>

  311. 

  312. <p>This option is incompatible with INSERT statements because it changes

  313. the way input sections are mapped to output sections.

  314. </p>

  315. <a name="index-_002d_002denable_002dnon_002dcontiguous_002dregions_002dwarnings"></a>

  316. </dd>

  317. <dt><code>--enable-non-contiguous-regions-warnings</code></dt>

  318. <dd><p>This option enables warnings when

  319. <code>--enable-non-contiguous-regions</code> allows possibly unexpected

  320. matches in sections mapping, potentially leading to silently

  321. discarding a section instead of failing because it does not fit any

  322. output region.

  323. </p>

  324. <a name="index-entry-point_002c-from-command-line"></a>

  325. <a name="index-_002de-entry"></a>

  326. <a name="index-_002d_002dentry_003dentry"></a>

  327. </dd>

  328. <dt><code>-e <var>entry</var></code></dt>

  329. <dt><code>--entry=<var>entry</var></code></dt>

  330. <dd><p>Use <var>entry</var> as the explicit symbol for beginning execution of your

  331. program, rather than the default entry point.  If there is no symbol

  332. named <var>entry</var>, the linker will try to parse <var>entry</var> as a number,

  333. and use that as the entry address (the number will be interpreted in

  334. base 10; you may use a leading &lsquo;<samp>0x</samp>&rsquo; for base 16, or a leading

  335. &lsquo;<samp>0</samp>&rsquo; for base 8).  See <a href="Entry-Point.html#Entry-Point">Entry Point</a>, for a discussion of defaults

  336. and other ways of specifying the entry point.

  337. </p>

  338. <a name="index-_002d_002dexclude_002dlibs"></a>

  339. </dd>

  340. <dt><code>--exclude-libs <var>lib</var>,<var>lib</var>,...</code></dt>

  341. <dd><p>Specifies a list of archive libraries from which symbols should not be automatically

  342. exported.  The library names may be delimited by commas or colons.  Specifying

  343. <code>--exclude-libs ALL</code> excludes symbols in all archive libraries from

  344. automatic export.  This option is available only for the i386 PE targeted

  345. port of the linker and for ELF targeted ports.  For i386 PE, symbols

  346. explicitly listed in a .def file are still exported, regardless of this

  347. option.  For ELF targeted ports, symbols affected by this option will

  348. be treated as hidden.

  349. </p>

  350. <a name="index-_002d_002dexclude_002dmodules_002dfor_002dimplib"></a>

  351. </dd>

  352. <dt><code>--exclude-modules-for-implib <var>module</var>,<var>module</var>,...</code></dt>

  353. <dd><p>Specifies a list of object files or archive members, from which symbols

  354. should not be automatically exported, but which should be copied wholesale

  355. into the import library being generated during the link.  The module names

  356. may be delimited by commas or colons, and must match exactly the filenames

  357. used by <code>ld</code> to open the files; for archive members, this is simply

  358. the member name, but for object files the name listed must include and

  359. match precisely any path used to specify the input file on the linker&rsquo;s

  360. command-line.  This option is available only for the i386 PE targeted port

  361. of the linker.  Symbols explicitly listed in a .def file are still exported,

  362. regardless of this option.

  363. </p>

  364. <a name="index-dynamic-symbol-table"></a>

  365. <a name="index-_002dE"></a>

  366. <a name="index-_002d_002dexport_002ddynamic"></a>

  367. <a name="index-_002d_002dno_002dexport_002ddynamic"></a>

  368. </dd>

  369. <dt><code>-E</code></dt>

  370. <dt><code>--export-dynamic</code></dt>

  371. <dt><code>--no-export-dynamic</code></dt>

  372. <dd><p>When creating a dynamically linked executable, using the <samp>-E</samp>

  373. option or the <samp>--export-dynamic</samp> option causes the linker to add

  374. all symbols to the dynamic symbol table.  The dynamic symbol table is the

  375. set of symbols which are visible from dynamic objects at run time.

  376. </p>

  377. <p>If you do not use either of these options (or use the

  378. <samp>--no-export-dynamic</samp> option to restore the default behavior), the

  379. dynamic symbol table will normally contain only those symbols which are

  380. referenced by some dynamic object mentioned in the link.

  381. </p>

  382. <p>If you use <code>dlopen</code> to load a dynamic object which needs to refer

  383. back to the symbols defined by the program, rather than some other

  384. dynamic object, then you will probably need to use this option when

  385. linking the program itself.

  386. </p>

  387. <p>You can also use the dynamic list to control what symbols should

  388. be added to the dynamic symbol table if the output format supports it.

  389. See the description of &lsquo;<samp>--dynamic-list</samp>&rsquo;.

  390. </p>

  391. <p>Note that this option is specific to ELF targeted ports.  PE targets

  392. support a similar function to export all symbols from a DLL or EXE; see

  393. the description of &lsquo;<samp>--export-all-symbols</samp>&rsquo; below.

  394. </p>

  395. <a name="index-_002d_002dexport_002ddynamic_002dsymbol_003dglob"></a>

  396. <a name="index-export-dynamic-symbol"></a>

  397. </dd>

  398. <dt><code>--export-dynamic-symbol=<var>glob</var></code></dt>

  399. <dd><p>When creating a dynamically linked executable, symbols matching

  400. <var>glob</var> will be added to the dynamic symbol table. When creating a

  401. shared library, references to symbols matching <var>glob</var> will not be

  402. bound to the definitions within the shared library. This option is a

  403. no-op when creating a shared library and &lsquo;<samp>-Bsymbolic</samp>&rsquo; or

  404. &lsquo;<samp>--dynamic-list</samp>&rsquo; are not specified. This option is only meaningful

  405. on ELF platforms which support shared libraries.

  406. </p>

  407. <a name="index-_002d_002dexport_002ddynamic_002dsymbol_002dlist_003dfile"></a>

  408. <a name="index-export-dynamic-symbol-list"></a>

  409. </dd>

  410. <dt><code>--export-dynamic-symbol-list=<var>file</var></code></dt>

  411. <dd><p>Specify a &lsquo;<samp>--export-dynamic-symbol</samp>&rsquo; for each pattern in the file.

  412. The format of the file is the same as the version node without

  413. scope and node name.  See <a href="VERSION.html#VERSION">VERSION</a> for more information.

  414. </p>

  415. <a name="index-big_002dendian-objects"></a>

  416. <a name="index-endianness"></a>

  417. <a name="index-_002dEB"></a>

  418. </dd>

  419. <dt><code>-EB</code></dt>

  420. <dd><p>Link big-endian objects.  This affects the default output format.

  421. </p>

  422. <a name="index-little_002dendian-objects"></a>

  423. <a name="index-_002dEL"></a>

  424. </dd>

  425. <dt><code>-EL</code></dt>

  426. <dd><p>Link little-endian objects.  This affects the default output format.

  427. </p>

  428. <a name="index-_002df-name"></a>

  429. <a name="index-_002d_002dauxiliary_003dname"></a>

  430. </dd>

  431. <dt><code>-f <var>name</var></code></dt>

  432. <dt><code>--auxiliary=<var>name</var></code></dt>

  433. <dd><p>When creating an ELF shared object, set the internal DT_AUXILIARY field

  434. to the specified name.  This tells the dynamic linker that the symbol

  435. table of the shared object should be used as an auxiliary filter on the

  436. symbol table of the shared object <var>name</var>.

  437. </p>

  438. <p>If you later link a program against this filter object, then, when you

  439. run the program, the dynamic linker will see the DT_AUXILIARY field.  If

  440. the dynamic linker resolves any symbols from the filter object, it will

  441. first check whether there is a definition in the shared object

  442. <var>name</var>.  If there is one, it will be used instead of the definition

  443. in the filter object.  The shared object <var>name</var> need not exist.

  444. Thus the shared object <var>name</var> may be used to provide an alternative

  445. implementation of certain functions, perhaps for debugging or for

  446. machine-specific performance.

  447. </p>

  448. <p>This option may be specified more than once.  The DT_AUXILIARY entries

  449. will be created in the order in which they appear on the command line.

  450. </p>

  451. <a name="index-_002dF-name"></a>

  452. <a name="index-_002d_002dfilter_003dname"></a>

  453. </dd>

  454. <dt><code>-F <var>name</var></code></dt>

  455. <dt><code>--filter=<var>name</var></code></dt>

  456. <dd><p>When creating an ELF shared object, set the internal DT_FILTER field to

  457. the specified name.  This tells the dynamic linker that the symbol table

  458. of the shared object which is being created should be used as a filter

  459. on the symbol table of the shared object <var>name</var>.

  460. </p>

  461. <p>If you later link a program against this filter object, then, when you

  462. run the program, the dynamic linker will see the DT_FILTER field.  The

  463. dynamic linker will resolve symbols according to the symbol table of the

  464. filter object as usual, but it will actually link to the definitions

  465. found in the shared object <var>name</var>.  Thus the filter object can be

  466. used to select a subset of the symbols provided by the object

  467. <var>name</var>.

  468. </p>

  469. <p>Some older linkers used the <samp>-F</samp> option throughout a compilation

  470. toolchain for specifying object-file format for both input and output

  471. object files.

  472. The <small>GNU</small> linker uses other mechanisms for this purpose: the

  473. <samp>-b</samp>, <samp>--format</samp>, <samp>--oformat</samp> options, the

  474. <code>TARGET</code> command in linker scripts, and the <code>GNUTARGET</code>

  475. environment variable.

  476. The <small>GNU</small> linker will ignore the <samp>-F</samp> option when not

  477. creating an ELF shared object.

  478. </p>

  479. <a name="index-finalization-function"></a>

  480. <a name="index-_002dfini_003dname"></a>

  481. </dd>

  482. <dt><code>-fini=<var>name</var></code></dt>

  483. <dd><p>When creating an ELF executable or shared object, call NAME when the

  484. executable or shared object is unloaded, by setting DT_FINI to the

  485. address of the function.  By default, the linker uses <code>_fini</code> as

  486. the function to call.

  487. </p>

  488. <a name="index-_002dg"></a>

  489. </dd>

  490. <dt><code>-g</code></dt>

  491. <dd><p>Ignored.  Provided for compatibility with other tools.

  492. </p>

  493. <a name="index-_002dG-value"></a>

  494. <a name="index-_002d_002dgpsize_003dvalue"></a>

  495. <a name="index-object-size"></a>

  496. </dd>

  497. <dt><code>-G <var>value</var></code></dt>

  498. <dt><code>--gpsize=<var>value</var></code></dt>

  499. <dd><p>Set the maximum size of objects to be optimized using the GP register to

  500. <var>size</var>.  This is only meaningful for object file formats such as

  501. MIPS ELF that support putting large and small objects into different

  502. sections.  This is ignored for other object file formats.

  503. </p>

  504. <a name="index-runtime-library-name"></a>

  505. <a name="index-_002dh-name"></a>

  506. <a name="index-_002dsoname_003dname"></a>

  507. </dd>

  508. <dt><code>-h <var>name</var></code></dt>

  509. <dt><code>-soname=<var>name</var></code></dt>

  510. <dd><p>When creating an ELF shared object, set the internal DT_SONAME field to

  511. the specified name.  When an executable is linked with a shared object

  512. which has a DT_SONAME field, then when the executable is run the dynamic

  513. linker will attempt to load the shared object specified by the DT_SONAME

  514. field rather than the using the file name given to the linker.

  515. </p>

  516. <a name="index-_002di"></a>

  517. <a name="index-incremental-link"></a>

  518. </dd>

  519. <dt><code>-i</code></dt>

  520. <dd><p>Perform an incremental link (same as option &lsquo;<samp>-r</samp>&rsquo;).

  521. </p>

  522. <a name="index-initialization-function"></a>

  523. <a name="index-_002dinit_003dname"></a>

  524. </dd>

  525. <dt><code>-init=<var>name</var></code></dt>

  526. <dd><p>When creating an ELF executable or shared object, call NAME when the

  527. executable or shared object is loaded, by setting DT_INIT to the address

  528. of the function.  By default, the linker uses <code>_init</code> as the

  529. function to call.

  530. </p>

  531. <a name="index-archive-files_002c-from-cmd-line"></a>

  532. <a name="index-_002dl-namespec"></a>

  533. <a name="index-_002d_002dlibrary_003dnamespec"></a>

  534. </dd>

  535. <dt><code>-l <var>namespec</var></code></dt>

  536. <dt><code>--library=<var>namespec</var></code></dt>

  537. <dd><p>Add the archive or object file specified by <var>namespec</var> to the

  538. list of files to link.  This option may be used any number of times.

  539. If <var>namespec</var> is of the form <samp>:<var>filename</var></samp>, <code>ld</code>

  540. will search the library path for a file called <var>filename</var>, otherwise it

  541. will search the library path for a file called <samp>lib<var>namespec</var>.a</samp>.

  542. </p>

  543. <p>On systems which support shared libraries, <code>ld</code> may also search for

  544. files other than <samp>lib<var>namespec</var>.a</samp>.  Specifically, on ELF

  545. and SunOS systems, <code>ld</code> will search a directory for a library

  546. called <samp>lib<var>namespec</var>.so</samp> before searching for one called

  547. <samp>lib<var>namespec</var>.a</samp>.  (By convention, a <code>.so</code> extension

  548. indicates a shared library.)  Note that this behavior does not apply

  549. to <samp>:<var>filename</var></samp>, which always specifies a file called

  550. <var>filename</var>.

  551. </p>

  552. <p>The linker will search an archive only once, at the location where it is

  553. specified on the command line.  If the archive defines a symbol which

  554. was undefined in some object which appeared before the archive on the

  555. command line, the linker will include the appropriate file(s) from the

  556. archive.  However, an undefined symbol in an object appearing later on

  557. the command line will not cause the linker to search the archive again.

  558. </p>

  559. <p>See the <samp>-(</samp> option for a way to force the linker to search

  560. archives multiple times.

  561. </p>

  562. <p>You may list the same archive multiple times on the command line.

  563. </p>

  564. <p>This type of archive searching is standard for Unix linkers.  However,

  565. if you are using <code>ld</code> on AIX, note that it is different from the

  566. behaviour of the AIX linker.

  567. </p>

  568. <a name="index-search-directory_002c-from-cmd-line"></a>

  569. <a name="index-_002dL-dir"></a>

  570. <a name="index-_002d_002dlibrary_002dpath_003ddir"></a>

  571. </dd>

  572. <dt><code>-L <var>searchdir</var></code></dt>

  573. <dt><code>--library-path=<var>searchdir</var></code></dt>

  574. <dd><p>Add path <var>searchdir</var> to the list of paths that <code>ld</code> will search

  575. for archive libraries and <code>ld</code> control scripts.  You may use this

  576. option any number of times.  The directories are searched in the order

  577. in which they are specified on the command line.  Directories specified

  578. on the command line are searched before the default directories.  All

  579. <samp>-L</samp> options apply to all <samp>-l</samp> options, regardless of the

  580. order in which the options appear.  <samp>-L</samp> options do not affect

  581. how <code>ld</code> searches for a linker script unless <samp>-T</samp>

  582. option is specified.

  583. </p>

  584. <p>If <var>searchdir</var> begins with <code>=</code> or <code>$SYSROOT</code>, then this

  585. prefix will be replaced by the <em>sysroot prefix</em>, controlled by the

  586. &lsquo;<samp>--sysroot</samp>&rsquo; option, or specified when the linker is configured.

  587. </p>

  588. <p>The default set of paths searched (without being specified with

  589. &lsquo;<samp>-L</samp>&rsquo;) depends on which emulation mode <code>ld</code> is using, and in

  590. some cases also on how it was configured.  See <a href="Environment.html#Environment">Environment</a>.

  591. </p>

  592. <p>The paths can also be specified in a link script with the

  593. <code>SEARCH_DIR</code> command.  Directories specified this way are searched

  594. at the point in which the linker script appears in the command line.

  595. </p>

  596. <a name="index-emulation"></a>

  597. <a name="index-_002dm-emulation"></a>

  598. </dd>

  599. <dt><code>-m <var>emulation</var></code></dt>

  600. <dd><p>Emulate the <var>emulation</var> linker.  You can list the available

  601. emulations with the &lsquo;<samp>--verbose</samp>&rsquo; or &lsquo;<samp>-V</samp>&rsquo; options.

  602. </p>

  603. <p>If the &lsquo;<samp>-m</samp>&rsquo; option is not used, the emulation is taken from the

  604. <code>LDEMULATION</code> environment variable, if that is defined.

  605. </p>

  606. <p>Otherwise, the default emulation depends upon how the linker was

  607. configured.

  608. </p>

  609. <a name="index-link-map"></a>

  610. <a name="index-_002dM"></a>

  611. <a name="index-_002d_002dprint_002dmap"></a>

  612. </dd>

  613. <dt><code>-M</code></dt>

  614. <dt><code>--print-map</code></dt>

  615. <dd><p>Print a link map to the standard output.  A link map provides

  616. information about the link, including the following:

  617. </p>

  618. <ul>

  619. <li> Where object files are mapped into memory.

  620. </li><li> How common symbols are allocated.

  621. </li><li> All archive members included in the link, with a mention of the symbol

  622. which caused the archive member to be brought in.

  623. </li><li> The values assigned to symbols.

  624. 

  625. <p>Note - symbols whose values are computed by an expression which

  626. involves a reference to a previous value of the same symbol may not

  627. have correct result displayed in the link map.  This is because the

  628. linker discards intermediate results and only retains the final value

  629. of an expression.  Under such circumstances the linker will display

  630. the final value enclosed by square brackets.  Thus for example a

  631. linker script containing:

  632. </p>

  633. <div class="smallexample">

  634. <pre class="smallexample">   foo = 1

  635.    foo = foo * 4

  636.    foo = foo + 8

  637. </pre></div>

  638. 

  639. <p>will produce the following output in the link map if the <samp>-M</samp>

  640. option is used:

  641. </p>

  642. <div class="smallexample">

  643. <pre class="smallexample">   0x00000001                foo = 0x1

  644.    [0x0000000c]                foo = (foo * 0x4)

  645.    [0x0000000c]                foo = (foo + 0x8)

  646. </pre></div>

  647. 

  648. <p>See <a href="Expressions.html#Expressions">Expressions</a> for more information about expressions in linker

  649. scripts.

  650. </p>

  651. </li><li> How GNU properties are merged.

  652. 

  653. <p>When the linker merges input .note.gnu.property sections into one output

  654. .note.gnu.property section, some properties are removed or updated.

  655. These actions are reported in the link map.  For example:

  656. </p>

  657. <div class="smallexample">

  658. <pre class="smallexample">Removed property 0xc0000002 to merge foo.o (0x1) and bar.o (not found)

  659. </pre></div>

  660. 

  661. <p>This indicates that property 0xc0000002 is removed from output when

  662. merging properties in  <samp>foo.o</samp>, whose property 0xc0000002 value

  663. is 0x1, and <samp>bar.o</samp>, which doesn&rsquo;t have property 0xc0000002.

  664. </p>

  665. <div class="smallexample">

  666. <pre class="smallexample">Updated property 0xc0010001 (0x1) to merge foo.o (0x1) and bar.o (0x1)

  667. </pre></div>

  668. 

  669. <p>This indicates that property 0xc0010001 value is updated to 0x1 in output

  670. when merging properties in  <samp>foo.o</samp>, whose 0xc0010001 property value

  671. is 0x1, and <samp>bar.o</samp>, whose 0xc0010001 property value is 0x1.

  672. </p></li></ul>

  673. 

  674. <a name="index-link-map-discarded"></a>

  675. <a name="index-_002d_002dprint_002dmap_002ddiscarded"></a>

  676. <a name="index-_002d_002dno_002dprint_002dmap_002ddiscarded"></a>

  677. </dd>

  678. <dt><code>--print-map-discarded</code></dt>

  679. <dt><code>--no-print-map-discarded</code></dt>

  680. <dd><p>Print (or do not print) the list of discarded and garbage collected sections

  681. in the link map.  Enabled by default.

  682. </p>

  683. <a name="index-_002dn"></a>

  684. <a name="index-read_002donly-text"></a>

  685. <a name="index-NMAGIC"></a>

  686. <a name="index-_002d_002dnmagic"></a>

  687. </dd>

  688. <dt><code>-n</code></dt>

  689. <dt><code>--nmagic</code></dt>

  690. <dd><p>Turn off page alignment of sections, and disable linking against shared

  691. libraries.  If the output format supports Unix style magic numbers,

  692. mark the output as <code>NMAGIC</code>.

  693. </p>

  694. <a name="index-_002dN"></a>

  695. <a name="index-_002d_002domagic"></a>

  696. <a name="index-read_002fwrite-from-cmd-line"></a>

  697. <a name="index-OMAGIC"></a>

  698. </dd>

  699. <dt><code>-N</code></dt>

  700. <dt><code>--omagic</code></dt>

  701. <dd><p>Set the text and data sections to be readable and writable.  Also, do

  702. not page-align the data segment, and disable linking against shared

  703. libraries.  If the output format supports Unix style magic numbers,

  704. mark the output as <code>OMAGIC</code>. Note: Although a writable text section

  705. is allowed for PE-COFF targets, it does not conform to the format

  706. specification published by Microsoft.

  707. </p>

  708. <a name="index-_002d_002dno_002domagic"></a>

  709. <a name="index-OMAGIC-1"></a>

  710. </dd>

  711. <dt><code>--no-omagic</code></dt>

  712. <dd><p>This option negates most of the effects of the <samp>-N</samp> option.  It

  713. sets the text section to be read-only, and forces the data segment to

  714. be page-aligned.  Note - this option does not enable linking against

  715. shared libraries.  Use <samp>-Bdynamic</samp> for this.

  716. </p>

  717. <a name="index-_002do-output"></a>

  718. <a name="index-_002d_002doutput_003doutput"></a>

  719. <a name="index-naming-the-output-file"></a>

  720. </dd>

  721. <dt><code>-o <var>output</var></code></dt>

  722. <dt><code>--output=<var>output</var></code></dt>

  723. <dd><p>Use <var>output</var> as the name for the program produced by <code>ld</code>; if this

  724. option is not specified, the name <samp>a.out</samp> is used by default.  The

  725. script command <code>OUTPUT</code> can also specify the output file name.

  726. </p>

  727. <a name="index-_002d_002ddependency_002dfile_003ddepfile"></a>

  728. <a name="index-dependency-file"></a>

  729. </dd>

  730. <dt><code>--dependency-file=<var>depfile</var></code></dt>

  731. <dd><p>Write a <em>dependency file</em> to <var>depfile</var>.  This file contains a rule

  732. suitable for <code>make</code> describing the output file and all the input files

  733. that were read to produce it.  The output is similar to the compiler&rsquo;s

  734. output with &lsquo;<samp>-M -MP</samp>&rsquo; (see <a href="http://gcc.gnu.org/onlinedocs/gcc/Preprocessor-Options.html#Preprocessor-Options">Options

  735. Controlling the Preprocessor</a> in <cite>Using the GNU Compiler

  736. Collection</cite>).  Note that there is no option like the compiler&rsquo;s &lsquo;<samp>-MM</samp>&rsquo;,

  737. to exclude &ldquo;system files&rdquo; (which is not a well-specified concept in the

  738. linker, unlike &ldquo;system headers&rdquo; in the compiler).  So the output from

  739. &lsquo;<samp>--dependency-file</samp>&rsquo; is always specific to the exact state of the

  740. installation where it was produced, and should not be copied into

  741. distributed makefiles without careful editing.

  742. </p>

  743. <a name="index-_002dO-level"></a>

  744. <a name="index-generating-optimized-output"></a>

  745. </dd>

  746. <dt><code>-O <var>level</var></code></dt>

  747. <dd><p>If <var>level</var> is a numeric values greater than zero <code>ld</code> optimizes

  748. the output.  This might take significantly longer and therefore probably

  749. should only be enabled for the final binary.  At the moment this

  750. option only affects ELF shared library generation.  Future releases of

  751. the linker may make more use of this option.  Also currently there is

  752. no difference in the linker&rsquo;s behaviour for different non-zero values

  753. of this option.  Again this may change with future releases.

  754. </p>

  755. <a name="index-_002dplugin-name"></a>

  756. </dd>

  757. <dt><code>-plugin <var>name</var></code></dt>

  758. <dd><p>Involve a plugin in the linking process.  The <var>name</var> parameter is

  759. the absolute filename of the plugin.  Usually this parameter is

  760. automatically added by the complier, when using link time

  761. optimization, but users can also add their own plugins if they so

  762. wish.

  763. </p>

  764. <p>Note that the location of the compiler originated plugins is different

  765. from the place where the <code>ar</code>, <code>nm</code> and

  766. <code>ranlib</code> programs search for their plugins.  In order for

  767. those commands to make use of a compiler based plugin it must first be

  768. copied into the <samp>${libdir}/bfd-plugins</samp> directory.  All gcc

  769. based linker plugins are backward compatible, so it is sufficient to

  770. just copy in the newest one.

  771. </p>

  772. <a name="index-_002d_002dpush_002dstate"></a>

  773. <a name="index-push-state-governing-input-file-handling"></a>

  774. </dd>

  775. <dt><code>--push-state</code></dt>

  776. <dd><p>The <samp>--push-state</samp> allows to preserve the current state of the

  777. flags which govern the input file handling so that they can all be

  778. restored with one corresponding <samp>--pop-state</samp> option.

  779. </p>

  780. <p>The option which are covered are: <samp>-Bdynamic</samp>, <samp>-Bstatic</samp>,

  781. <samp>-dn</samp>, <samp>-dy</samp>, <samp>-call_shared</samp>, <samp>-non_shared</samp>,

  782. <samp>-static</samp>, <samp>-N</samp>, <samp>-n</samp>, <samp>--whole-archive</samp>,

  783. <samp>--no-whole-archive</samp>, <samp>-r</samp>, <samp>-Ur</samp>,

  784. <samp>--copy-dt-needed-entries</samp>, <samp>--no-copy-dt-needed-entries</samp>,

  785. <samp>--as-needed</samp>, <samp>--no-as-needed</samp>, and <samp>-a</samp>.

  786. </p>

  787. <p>One target for this option are specifications for <samp>pkg-config</samp>.  When

  788. used with the <samp>--libs</samp> option all possibly needed libraries are

  789. listed and then possibly linked with all the time.  It is better to return

  790. something as follows:

  791. </p>

  792. <div class="smallexample">

  793. <pre class="smallexample">-Wl,--push-state,--as-needed -libone -libtwo -Wl,--pop-state

  794. </pre></div>

  795. 

  796. <a name="index-_002d_002dpop_002dstate"></a>

  797. <a name="index-pop-state-governing-input-file-handling"></a>

  798. </dd>

  799. <dt><code>--pop-state</code></dt>

  800. <dd><p>Undoes the effect of &ndash;push-state, restores the previous values of the

  801. flags governing input file handling.

  802. </p>

  803. <a name="index-_002dq"></a>

  804. <a name="index-_002d_002demit_002drelocs"></a>

  805. <a name="index-retain-relocations-in-final-executable"></a>

  806. </dd>

  807. <dt><code>-q</code></dt>

  808. <dt><code>--emit-relocs</code></dt>

  809. <dd><p>Leave relocation sections and contents in fully linked executables.

  810. Post link analysis and optimization tools may need this information in

  811. order to perform correct modifications of executables.  This results

  812. in larger executables.

  813. </p>

  814. <p>This option is currently only supported on ELF platforms.

  815. </p>

  816. <a name="index-_002d_002dforce_002ddynamic"></a>

  817. <a name="index-forcing-the-creation-of-dynamic-sections"></a>

  818. </dd>

  819. <dt><code>--force-dynamic</code></dt>

  820. <dd><p>Force the output file to have dynamic sections.  This option is specific

  821. to VxWorks targets.

  822. </p>

  823. <a name="index-partial-link"></a>

  824. <a name="index-relocatable-output"></a>

  825. <a name="index-_002dr"></a>

  826. <a name="index-_002d_002drelocatable"></a>

  827. </dd>

  828. <dt><code>-r</code></dt>

  829. <dt><code>--relocatable</code></dt>

  830. <dd><p>Generate relocatable output&mdash;i.e., generate an output file that can in

  831. turn serve as input to <code>ld</code>.  This is often called <em>partial

  832. linking</em>.  As a side effect, in environments that support standard Unix

  833. magic numbers, this option also sets the output file&rsquo;s magic number to

  834. <code>OMAGIC</code>.

  835. If this option is not specified, an absolute file is produced.  When

  836. linking C++ programs, this option <em>will not</em> resolve references to

  837. constructors; to do that, use &lsquo;<samp>-Ur</samp>&rsquo;.

  838. </p>

  839. <p>When an input file does not have the same format as the output file,

  840. partial linking is only supported if that input file does not contain any

  841. relocations.  Different output formats can have further restrictions; for

  842. example some <code>a.out</code>-based formats do not support partial linking

  843. with input files in other formats at all.

  844. </p>

  845. <p>This option does the same thing as &lsquo;<samp>-i</samp>&rsquo;.

  846. </p>

  847. <a name="index-_002dR-file"></a>

  848. <a name="index-_002d_002djust_002dsymbols_003dfile"></a>

  849. <a name="index-symbol_002donly-input"></a>

  850. </dd>

  851. <dt><code>-R <var>filename</var></code></dt>

  852. <dt><code>--just-symbols=<var>filename</var></code></dt>

  853. <dd><p>Read symbol names and their addresses from <var>filename</var>, but do not

  854. relocate it or include it in the output.  This allows your output file

  855. to refer symbolically to absolute locations of memory defined in other

  856. programs.  You may use this option more than once.

  857. </p>

  858. <p>For compatibility with other ELF linkers, if the <samp>-R</samp> option is

  859. followed by a directory name, rather than a file name, it is treated as

  860. the <samp>-rpath</samp> option.

  861. </p>

  862. <a name="index-_002ds"></a>

  863. <a name="index-_002d_002dstrip_002dall"></a>

  864. <a name="index-strip-all-symbols"></a>

  865. </dd>

  866. <dt><code>-s</code></dt>

  867. <dt><code>--strip-all</code></dt>

  868. <dd><p>Omit all symbol information from the output file.

  869. </p>

  870. <a name="index-_002dS"></a>

  871. <a name="index-_002d_002dstrip_002ddebug"></a>

  872. <a name="index-strip-debugger-symbols"></a>

  873. </dd>

  874. <dt><code>-S</code></dt>

  875. <dt><code>--strip-debug</code></dt>

  876. <dd><p>Omit debugger symbol information (but not all symbols) from the output file.

  877. </p>

  878. <a name="index-_002d_002dstrip_002ddiscarded"></a>

  879. <a name="index-_002d_002dno_002dstrip_002ddiscarded"></a>

  880. </dd>

  881. <dt><code>--strip-discarded</code></dt>

  882. <dt><code>--no-strip-discarded</code></dt>

  883. <dd><p>Omit (or do not omit) global symbols defined in discarded sections.

  884. Enabled by default.

  885. </p>

  886. <a name="index-_002dt"></a>

  887. <a name="index-_002d_002dtrace"></a>

  888. <a name="index-input-files_002c-displaying"></a>

  889. </dd>

  890. <dt><code>-t</code></dt>

  891. <dt><code>--trace</code></dt>

  892. <dd><p>Print the names of the input files as <code>ld</code> processes them.  If

  893. &lsquo;<samp>-t</samp>&rsquo; is given twice then members within archives are also printed.

  894. &lsquo;<samp>-t</samp>&rsquo; output is useful to generate a list of all the object files

  895. and scripts involved in linking, for example, when packaging files for

  896. a linker bug report.

  897. </p>

  898. <a name="index-_002dT-script"></a>

  899. <a name="index-_002d_002dscript_003dscript"></a>

  900. <a name="index-script-files"></a>

  901. </dd>

  902. <dt><code>-T <var>scriptfile</var></code></dt>

  903. <dt><code>--script=<var>scriptfile</var></code></dt>

  904. <dd><p>Use <var>scriptfile</var> as the linker script.  This script replaces

  905. <code>ld</code>&rsquo;s default linker script (rather than adding to it), so

  906. <var>commandfile</var> must specify everything necessary to describe the

  907. output file.  See <a href="Scripts.html#Scripts">Scripts</a>.  If <var>scriptfile</var> does not exist in

  908. the current directory, <code>ld</code> looks for it in the directories

  909. specified by any preceding &lsquo;<samp>-L</samp>&rsquo; options.  Multiple &lsquo;<samp>-T</samp>&rsquo;

  910. options accumulate.

  911. </p>

  912. <a name="index-_002ddT-script"></a>

  913. <a name="index-_002d_002ddefault_002dscript_003dscript"></a>

  914. <a name="index-script-files-1"></a>

  915. </dd>

  916. <dt><code>-dT <var>scriptfile</var></code></dt>

  917. <dt><code>--default-script=<var>scriptfile</var></code></dt>

  918. <dd><p>Use <var>scriptfile</var> as the default linker script.  See <a href="Scripts.html#Scripts">Scripts</a>.

  919. </p>

  920. <p>This option is similar to the <samp>--script</samp> option except that

  921. processing of the script is delayed until after the rest of the

  922. command line has been processed.  This allows options placed after the

  923. <samp>--default-script</samp> option on the command line to affect the

  924. behaviour of the linker script, which can be important when the linker

  925. command line cannot be directly controlled by the user.  (eg because

  926. the command line is being constructed by another tool, such as

  927. &lsquo;<samp>gcc</samp>&rsquo;).

  928. </p>

  929. <a name="index-_002du-symbol"></a>

  930. <a name="index-_002d_002dundefined_003dsymbol"></a>

  931. <a name="index-undefined-symbol"></a>

  932. </dd>

  933. <dt><code>-u <var>symbol</var></code></dt>

  934. <dt><code>--undefined=<var>symbol</var></code></dt>

  935. <dd><p>Force <var>symbol</var> to be entered in the output file as an undefined

  936. symbol.  Doing this may, for example, trigger linking of additional

  937. modules from standard libraries.  &lsquo;<samp>-u</samp>&rsquo; may be repeated with

  938. different option arguments to enter additional undefined symbols.  This

  939. option is equivalent to the <code>EXTERN</code> linker script command.

  940. </p>

  941. <p>If this option is being used to force additional modules to be pulled

  942. into the link, and if it is an error for the symbol to remain

  943. undefined, then the option <samp>--require-defined</samp> should be used

  944. instead.

  945. </p>

  946. <a name="index-_002d_002drequire_002ddefined_003dsymbol"></a>

  947. <a name="index-symbols_002c-require-defined"></a>

  948. <a name="index-defined-symbol"></a>

  949. </dd>

  950. <dt><code>--require-defined=<var>symbol</var></code></dt>

  951. <dd><p>Require that <var>symbol</var> is defined in the output file.  This option

  952. is the same as option <samp>--undefined</samp> except that if <var>symbol</var>

  953. is not defined in the output file then the linker will issue an error

  954. and exit.  The same effect can be achieved in a linker script by using

  955. <code>EXTERN</code>, <code>ASSERT</code> and <code>DEFINED</code> together.  This option

  956. can be used multiple times to require additional symbols.

  957. </p>

  958. <a name="index-_002dUr"></a>

  959. <a name="index-constructors"></a>

  960. </dd>

  961. <dt><code>-Ur</code></dt>

  962. <dd><p>For anything other than C++ programs, this option is equivalent to

  963. &lsquo;<samp>-r</samp>&rsquo;: it generates relocatable output&mdash;i.e., an output file that can in

  964. turn serve as input to <code>ld</code>.  When linking C++ programs, &lsquo;<samp>-Ur</samp>&rsquo;

  965. <em>does</em> resolve references to constructors, unlike &lsquo;<samp>-r</samp>&rsquo;.

  966. It does not work to use &lsquo;<samp>-Ur</samp>&rsquo; on files that were themselves linked

  967. with &lsquo;<samp>-Ur</samp>&rsquo;; once the constructor table has been built, it cannot

  968. be added to.  Use &lsquo;<samp>-Ur</samp>&rsquo; only for the last partial link, and

  969. &lsquo;<samp>-r</samp>&rsquo; for the others.

  970. </p>

  971. <a name="index-_002d_002dorphan_002dhandling_003dMODE"></a>

  972. <a name="index-orphan-sections"></a>

  973. <a name="index-sections_002c-orphan"></a>

  974. </dd>

  975. <dt><code>--orphan-handling=<var>MODE</var></code></dt>

  976. <dd><p>Control how orphan sections are handled.  An orphan section is one not

  977. specifically mentioned in a linker script.  See <a href="Orphan-Sections.html#Orphan-Sections">Orphan Sections</a>.

  978. </p>

  979. <p><var>MODE</var> can have any of the following values:

  980. </p>

  981. <dl compact="compact">

  982. <dt><code>place</code></dt>

  983. <dd><p>Orphan sections are placed into a suitable output section following

  984. the strategy described in <a href="Orphan-Sections.html#Orphan-Sections">Orphan Sections</a>.  The option

  985. &lsquo;<samp>--unique</samp>&rsquo; also affects how sections are placed.

  986. </p>

  987. </dd>

  988. <dt><code>discard</code></dt>

  989. <dd><p>All orphan sections are discarded, by placing them in the

  990. &lsquo;<samp>/DISCARD/</samp>&rsquo; section (see <a href="Output-Section-Discarding.html#Output-Section-Discarding">Output Section Discarding</a>).

  991. </p>

  992. </dd>

  993. <dt><code>warn</code></dt>

  994. <dd><p>The linker will place the orphan section as for <code>place</code> and also

  995. issue a warning.

  996. </p>

  997. </dd>

  998. <dt><code>error</code></dt>

  999. <dd><p>The linker will exit with an error if any orphan section is found.

  1000. </p></dd>

  1001. </dl>

  1002. 

  1003. <p>The default if &lsquo;<samp>--orphan-handling</samp>&rsquo; is not given is <code>place</code>.

  1004. </p>

  1005. <a name="index-_002d_002dunique_005b_003dSECTION_005d"></a>

  1006. </dd>

  1007. <dt><code>--unique[=<var>SECTION</var>]</code></dt>

  1008. <dd><p>Creates a separate output section for every input section matching

  1009. <var>SECTION</var>, or if the optional wildcard <var>SECTION</var> argument is

  1010. missing, for every orphan input section.  An orphan section is one not

  1011. specifically mentioned in a linker script.  You may use this option

  1012. multiple times on the command line;  It prevents the normal merging of

  1013. input sections with the same name, overriding output section assignments

  1014. in a linker script.

  1015. </p>

  1016. <a name="index-_002dv"></a>

  1017. <a name="index-_002dV"></a>

  1018. <a name="index-_002d_002dversion"></a>

  1019. <a name="index-version"></a>

  1020. </dd>

  1021. <dt><code>-v</code></dt>

  1022. <dt><code>--version</code></dt>

  1023. <dt><code>-V</code></dt>

  1024. <dd><p>Display the version number for <code>ld</code>.  The <samp>-V</samp> option also

  1025. lists the supported emulations.

  1026. </p>

  1027. <a name="index-_002dx"></a>

  1028. <a name="index-_002d_002ddiscard_002dall"></a>

  1029. <a name="index-deleting-local-symbols"></a>

  1030. </dd>

  1031. <dt><code>-x</code></dt>

  1032. <dt><code>--discard-all</code></dt>

  1033. <dd><p>Delete all local symbols.

  1034. </p>

  1035. <a name="index-_002dX"></a>

  1036. <a name="index-_002d_002ddiscard_002dlocals"></a>

  1037. <a name="index-local-symbols_002c-deleting"></a>

  1038. </dd>

  1039. <dt><code>-X</code></dt>

  1040. <dt><code>--discard-locals</code></dt>

  1041. <dd><p>Delete all temporary local symbols.  (These symbols start with

  1042. system-specific local label prefixes, typically &lsquo;<samp>.L</samp>&rsquo; for ELF systems

  1043. or &lsquo;<samp>L</samp>&rsquo; for traditional a.out systems.)

  1044. </p>

  1045. <a name="index-_002dy-symbol"></a>

  1046. <a name="index-_002d_002dtrace_002dsymbol_003dsymbol"></a>

  1047. <a name="index-symbol-tracing"></a>

  1048. </dd>

  1049. <dt><code>-y <var>symbol</var></code></dt>

  1050. <dt><code>--trace-symbol=<var>symbol</var></code></dt>

  1051. <dd><p>Print the name of each linked file in which <var>symbol</var> appears.  This

  1052. option may be given any number of times.  On many systems it is necessary

  1053. to prepend an underscore.

  1054. </p>

  1055. <p>This option is useful when you have an undefined symbol in your link but

  1056. don&rsquo;t know where the reference is coming from.

  1057. </p>

  1058. <a name="index-_002dY-path"></a>

  1059. </dd>

  1060. <dt><code>-Y <var>path</var></code></dt>

  1061. <dd><p>Add <var>path</var> to the default library search path.  This option exists

  1062. for Solaris compatibility.

  1063. </p>

  1064. <a name="index-_002dz-keyword"></a>

  1065. </dd>

  1066. <dt><code>-z <var>keyword</var></code></dt>

  1067. <dd><p>The recognized keywords are:

  1068. </p><dl compact="compact">

  1069. <dt>&lsquo;<samp>bndplt</samp>&rsquo;</dt>

  1070. <dd><p>Always generate BND prefix in PLT entries. Supported for Linux/x86_64.

  1071. </p>

  1072. </dd>

  1073. <dt>&lsquo;<samp>call-nop=prefix-addr</samp>&rsquo;</dt>

  1074. <dt>&lsquo;<samp>call-nop=suffix-nop</samp>&rsquo;</dt>

  1075. <dt>&lsquo;<samp>call-nop=prefix-<var>byte</var></samp>&rsquo;</dt>

  1076. <dt>&lsquo;<samp>call-nop=suffix-<var>byte</var></samp>&rsquo;</dt>

  1077. <dd><p>Specify the 1-byte <code>NOP</code> padding when transforming indirect call

  1078. to a locally defined function, foo, via its GOT slot.

  1079. <samp>call-nop=prefix-addr</samp> generates <code>0x67 call foo</code>.

  1080. <samp>call-nop=suffix-nop</samp> generates <code>call foo 0x90</code>.

  1081. <samp>call-nop=prefix-<var>byte</var></samp> generates <code><var>byte</var> call foo</code>.

  1082. <samp>call-nop=suffix-<var>byte</var></samp> generates <code>call foo <var>byte</var></code>.

  1083. Supported for i386 and x86_64.

  1084. </p>

  1085. </dd>

  1086. <dt>&lsquo;<samp>cet-report=none</samp>&rsquo;</dt>

  1087. <dt>&lsquo;<samp>cet-report=warning</samp>&rsquo;</dt>

  1088. <dt>&lsquo;<samp>cet-report=error</samp>&rsquo;</dt>

  1089. <dd><p>Specify how to report the missing GNU_PROPERTY_X86_FEATURE_1_IBT and

  1090. GNU_PROPERTY_X86_FEATURE_1_SHSTK properties in input .note.gnu.property

  1091. section.  <samp>cet-report=none</samp>, which is the default, will make the

  1092. linker not report missing properties in input files.

  1093. <samp>cet-report=warning</samp> will make the linker issue a warning for

  1094. missing properties in input files.  <samp>cet-report=error</samp> will make

  1095. the linker issue an error for missing properties in input files.

  1096. Note that <samp>ibt</samp> will turn off the missing

  1097. GNU_PROPERTY_X86_FEATURE_1_IBT property report and <samp>shstk</samp> will

  1098. turn off the missing GNU_PROPERTY_X86_FEATURE_1_SHSTK property report.

  1099. Supported for Linux/i386 and Linux/x86_64.

  1100. </p>

  1101. </dd>

  1102. <dt>&lsquo;<samp>combreloc</samp>&rsquo;</dt>

  1103. <dt>&lsquo;<samp>nocombreloc</samp>&rsquo;</dt>

  1104. <dd><p>Combine multiple dynamic relocation sections and sort to improve

  1105. dynamic symbol lookup caching.  Do not do this if &lsquo;<samp>nocombreloc</samp>&rsquo;.

  1106. </p>

  1107. </dd>

  1108. <dt>&lsquo;<samp>common</samp>&rsquo;</dt>

  1109. <dt>&lsquo;<samp>nocommon</samp>&rsquo;</dt>

  1110. <dd><p>Generate common symbols with STT_COMMON type during a relocatable

  1111. link.  Use STT_OBJECT type if &lsquo;<samp>nocommon</samp>&rsquo;.

  1112. </p>

  1113. </dd>

  1114. <dt>&lsquo;<samp>common-page-size=<var>value</var></samp>&rsquo;</dt>

  1115. <dd><p>Set the page size most commonly used to <var>value</var>.  Memory image

  1116. layout will be optimized to minimize memory pages if the system is

  1117. using pages of this size.

  1118. </p>

  1119. </dd>

  1120. <dt>&lsquo;<samp>defs</samp>&rsquo;</dt>

  1121. <dd><p>Report unresolved symbol references from regular object files.  This

  1122. is done even if the linker is creating a non-symbolic shared library.

  1123. This option is the inverse of &lsquo;<samp>-z undefs</samp>&rsquo;.

  1124. </p>

  1125. </dd>

  1126. <dt>&lsquo;<samp>dynamic-undefined-weak</samp>&rsquo;</dt>

  1127. <dt>&lsquo;<samp>nodynamic-undefined-weak</samp>&rsquo;</dt>

  1128. <dd><p>Make undefined weak symbols dynamic when building a dynamic object,

  1129. if they are referenced from a regular object file and not forced local

  1130. by symbol visibility or versioning.  Do not make them dynamic if

  1131. &lsquo;<samp>nodynamic-undefined-weak</samp>&rsquo;.  If neither option is given, a target

  1132. may default to either option being in force, or make some other

  1133. selection of undefined weak symbols dynamic.  Not all targets support

  1134. these options.

  1135. </p>

  1136. </dd>

  1137. <dt>&lsquo;<samp>execstack</samp>&rsquo;</dt>

  1138. <dd><p>Marks the object as requiring executable stack.

  1139. </p>

  1140. </dd>

  1141. <dt>&lsquo;<samp>global</samp>&rsquo;</dt>

  1142. <dd><p>This option is only meaningful when building a shared object.  It makes

  1143. the symbols defined by this shared object available for symbol resolution

  1144. of subsequently loaded libraries.

  1145. </p>

  1146. </dd>

  1147. <dt>&lsquo;<samp>globalaudit</samp>&rsquo;</dt>

  1148. <dd><p>This option is only meaningful when building a dynamic executable.

  1149. This option marks the executable as requiring global auditing by

  1150. setting the <code>DF_1_GLOBAUDIT</code> bit in the <code>DT_FLAGS_1</code> dynamic

  1151. tag.  Global auditing requires that any auditing library defined via

  1152. the <samp>--depaudit</samp> or <samp>-P</samp> command-line options be run for

  1153. all dynamic objects loaded by the application.

  1154. </p>

  1155. </dd>

  1156. <dt>&lsquo;<samp>ibtplt</samp>&rsquo;</dt>

  1157. <dd><p>Generate Intel Indirect Branch Tracking (IBT) enabled PLT entries.

  1158. Supported for Linux/i386 and Linux/x86_64.

  1159. </p>

  1160. </dd>

  1161. <dt>&lsquo;<samp>ibt</samp>&rsquo;</dt>

  1162. <dd><p>Generate GNU_PROPERTY_X86_FEATURE_1_IBT in .note.gnu.property section

  1163. to indicate compatibility with IBT.  This also implies <samp>ibtplt</samp>.

  1164. Supported for Linux/i386 and Linux/x86_64.

  1165. </p>

  1166. </dd>

  1167. <dt>&lsquo;<samp>initfirst</samp>&rsquo;</dt>

  1168. <dd><p>This option is only meaningful when building a shared object.

  1169. It marks the object so that its runtime initialization will occur

  1170. before the runtime initialization of any other objects brought into

  1171. the process at the same time.  Similarly the runtime finalization of

  1172. the object will occur after the runtime finalization of any other

  1173. objects.

  1174. </p>

  1175. </dd>

  1176. <dt>&lsquo;<samp>interpose</samp>&rsquo;</dt>

  1177. <dd><p>Specify that the dynamic loader should modify its symbol search order

  1178. so that symbols in this shared library interpose all other shared

  1179. libraries not so marked.

  1180. </p>

  1181. </dd>

  1182. <dt>&lsquo;<samp>lazy</samp>&rsquo;</dt>

  1183. <dd><p>When generating an executable or shared library, mark it to tell the

  1184. dynamic linker to defer function call resolution to the point when

  1185. the function is called (lazy binding), rather than at load time.

  1186. Lazy binding is the default.

  1187. </p>

  1188. </dd>

  1189. <dt>&lsquo;<samp>loadfltr</samp>&rsquo;</dt>

  1190. <dd><p>Specify that the object&rsquo;s filters be processed immediately at runtime.

  1191. </p>

  1192. </dd>

  1193. <dt>&lsquo;<samp>max-page-size=<var>value</var></samp>&rsquo;</dt>

  1194. <dd><p>Set the maximum memory page size supported to <var>value</var>.

  1195. </p>

  1196. </dd>

  1197. <dt>&lsquo;<samp>muldefs</samp>&rsquo;</dt>

  1198. <dd><p>Allow multiple definitions.

  1199. </p>

  1200. </dd>

  1201. <dt>&lsquo;<samp>nocopyreloc</samp>&rsquo;</dt>

  1202. <dd><p>Disable linker generated .dynbss variables used in place of variables

  1203. defined in shared libraries.  May result in dynamic text relocations.

  1204. </p>

  1205. </dd>

  1206. <dt>&lsquo;<samp>nodefaultlib</samp>&rsquo;</dt>

  1207. <dd><p>Specify that the dynamic loader search for dependencies of this object

  1208. should ignore any default library search paths.

  1209. </p>

  1210. </dd>

  1211. <dt>&lsquo;<samp>nodelete</samp>&rsquo;</dt>

  1212. <dd><p>Specify that the object shouldn&rsquo;t be unloaded at runtime.

  1213. </p>

  1214. </dd>

  1215. <dt>&lsquo;<samp>nodlopen</samp>&rsquo;</dt>

  1216. <dd><p>Specify that the object is not available to <code>dlopen</code>.

  1217. </p>

  1218. </dd>

  1219. <dt>&lsquo;<samp>nodump</samp>&rsquo;</dt>

  1220. <dd><p>Specify that the object can not be dumped by <code>dldump</code>.

  1221. </p>

  1222. </dd>

  1223. <dt>&lsquo;<samp>noexecstack</samp>&rsquo;</dt>

  1224. <dd><p>Marks the object as not requiring executable stack.

  1225. </p>

  1226. </dd>

  1227. <dt>&lsquo;<samp>noextern-protected-data</samp>&rsquo;</dt>

  1228. <dd><p>Don&rsquo;t treat protected data symbols as external when building a shared

  1229. library.  This option overrides the linker backend default.  It can be

  1230. used to work around incorrect relocations against protected data symbols

  1231. generated by compiler.  Updates on protected data symbols by another

  1232. module aren&rsquo;t visible to the resulting shared library.  Supported for

  1233. i386 and x86-64.

  1234. </p>

  1235. </dd>

  1236. <dt>&lsquo;<samp>noreloc-overflow</samp>&rsquo;</dt>

  1237. <dd><p>Disable relocation overflow check.  This can be used to disable

  1238. relocation overflow check if there will be no dynamic relocation

  1239. overflow at run-time.  Supported for x86_64.

  1240. </p>

  1241. </dd>

  1242. <dt>&lsquo;<samp>now</samp>&rsquo;</dt>

  1243. <dd><p>When generating an executable or shared library, mark it to tell the

  1244. dynamic linker to resolve all symbols when the program is started, or

  1245. when the shared library is loaded by dlopen, instead of deferring

  1246. function call resolution to the point when the function is first

  1247. called.

  1248. </p>

  1249. </dd>

  1250. <dt>&lsquo;<samp>origin</samp>&rsquo;</dt>

  1251. <dd><p>Specify that the object requires &lsquo;<samp>$ORIGIN</samp>&rsquo; handling in paths.

  1252. </p>

  1253. </dd>

  1254. <dt>&lsquo;<samp>relro</samp>&rsquo;</dt>

  1255. <dt>&lsquo;<samp>norelro</samp>&rsquo;</dt>

  1256. <dd><p>Create an ELF <code>PT_GNU_RELRO</code> segment header in the object.  This

  1257. specifies a memory segment that should be made read-only after

  1258. relocation, if supported.  Specifying &lsquo;<samp>common-page-size</samp>&rsquo; smaller

  1259. than the system page size will render this protection ineffective.

  1260. Don&rsquo;t create an ELF <code>PT_GNU_RELRO</code> segment if &lsquo;<samp>norelro</samp>&rsquo;.

  1261. </p>

  1262. </dd>

  1263. <dt>&lsquo;<samp>separate-code</samp>&rsquo;</dt>

  1264. <dt>&lsquo;<samp>noseparate-code</samp>&rsquo;</dt>

  1265. <dd><p>Create separate code <code>PT_LOAD</code> segment header in the object.  This

  1266. specifies a memory segment that should contain only instructions and must

  1267. be in wholly disjoint pages from any other data.  Don&rsquo;t create separate

  1268. code <code>PT_LOAD</code> segment if &lsquo;<samp>noseparate-code</samp>&rsquo; is used.

  1269. </p>

  1270. </dd>

  1271. <dt>&lsquo;<samp>shstk</samp>&rsquo;</dt>

  1272. <dd><p>Generate GNU_PROPERTY_X86_FEATURE_1_SHSTK in .note.gnu.property section

  1273. to indicate compatibility with Intel Shadow Stack.  Supported for

  1274. Linux/i386 and Linux/x86_64.

  1275. </p>

  1276. </dd>

  1277. <dt>&lsquo;<samp>stack-size=<var>value</var></samp>&rsquo;</dt>

  1278. <dd><p>Specify a stack size for an ELF <code>PT_GNU_STACK</code> segment.

  1279. Specifying zero will override any default non-zero sized

  1280. <code>PT_GNU_STACK</code> segment creation.

  1281. </p>

  1282. </dd>

  1283. <dt>&lsquo;<samp>start-stop-visibility=<var>value</var></samp>&rsquo;</dt>

  1284. <dd><a name="index-visibility"></a>

  1285. <a name="index-ELF-symbol-visibility"></a>

  1286. <p>Specify the ELF symbol visibility for synthesized

  1287. <code>__start_SECNAME</code> and <code>__stop_SECNAME</code> symbols (see <a href="Input-Section-Example.html#Input-Section-Example">Input Section Example</a>).  <var>value</var> must be exactly &lsquo;<samp>default</samp>&rsquo;,

  1288. &lsquo;<samp>internal</samp>&rsquo;, &lsquo;<samp>hidden</samp>&rsquo;, or &lsquo;<samp>protected</samp>&rsquo;.  If no &lsquo;<samp>-z

  1289. start-stop-visibility</samp>&rsquo; option is given, &lsquo;<samp>protected</samp>&rsquo; is used for

  1290. compatibility with historical practice.  However, it&rsquo;s highly

  1291. recommended to use &lsquo;<samp>-z start-stop-visibility=hidden</samp>&rsquo; in new

  1292. programs and shared libraries so that these symbols are not exported

  1293. between shared objects, which is not usually what&rsquo;s intended.

  1294. </p>

  1295. </dd>

  1296. <dt>&lsquo;<samp>text</samp>&rsquo;</dt>

  1297. <dt>&lsquo;<samp>notext</samp>&rsquo;</dt>

  1298. <dt>&lsquo;<samp>textoff</samp>&rsquo;</dt>

  1299. <dd><p>Report an error if DT_TEXTREL is set, i.e., if the position-independent

  1300. or shared object has dynamic relocations in read-only sections.  Don&rsquo;t

  1301. report an error if &lsquo;<samp>notext</samp>&rsquo; or &lsquo;<samp>textoff</samp>&rsquo;.

  1302. </p>

  1303. </dd>

  1304. <dt>&lsquo;<samp>undefs</samp>&rsquo;</dt>

  1305. <dd><p>Do not report unresolved symbol references from regular object files,

  1306. either when creating an executable, or when creating a shared library.

  1307. This option is the inverse of &lsquo;<samp>-z defs</samp>&rsquo;.

  1308. </p>

  1309. </dd>

  1310. </dl>

  1311. 

  1312. <p>Other keywords are ignored for Solaris compatibility.

  1313. </p>

  1314. <a name="index-_002d_0028"></a>

  1315. <a name="index-groups-of-archives"></a>

  1316. </dd>

  1317. <dt><code>-( <var>archives</var> -)</code></dt>

  1318. <dt><code>--start-group <var>archives</var> --end-group</code></dt>

  1319. <dd><p>The <var>archives</var> should be a list of archive files.  They may be

  1320. either explicit file names, or &lsquo;<samp>-l</samp>&rsquo; options.

  1321. </p>

  1322. <p>The specified archives are searched repeatedly until no new undefined

  1323. references are created.  Normally, an archive is searched only once in

  1324. the order that it is specified on the command line.  If a symbol in that

  1325. archive is needed to resolve an undefined symbol referred to by an

  1326. object in an archive that appears later on the command line, the linker

  1327. would not be able to resolve that reference.  By grouping the archives,

  1328. they will all be searched repeatedly until all possible references are

  1329. resolved.

  1330. </p>

  1331. <p>Using this option has a significant performance cost.  It is best to use

  1332. it only when there are unavoidable circular references between two or

  1333. more archives.

  1334. </p>

  1335. <a name="index-_002d_002daccept_002dunknown_002dinput_002darch"></a>

  1336. <a name="index-_002d_002dno_002daccept_002dunknown_002dinput_002darch"></a>

  1337. </dd>

  1338. <dt><code>--accept-unknown-input-arch</code></dt>

  1339. <dt><code>--no-accept-unknown-input-arch</code></dt>

  1340. <dd><p>Tells the linker to accept input files whose architecture cannot be

  1341. recognised.  The assumption is that the user knows what they are doing

  1342. and deliberately wants to link in these unknown input files.  This was

  1343. the default behaviour of the linker, before release 2.14.  The default

  1344. behaviour from release 2.14 onwards is to reject such input files, and

  1345. so the &lsquo;<samp>--accept-unknown-input-arch</samp>&rsquo; option has been added to

  1346. restore the old behaviour.

  1347. </p>

  1348. <a name="index-_002d_002das_002dneeded"></a>

  1349. <a name="index-_002d_002dno_002das_002dneeded"></a>

  1350. </dd>

  1351. <dt><code>--as-needed</code></dt>

  1352. <dt><code>--no-as-needed</code></dt>

  1353. <dd><p>This option affects ELF DT_NEEDED tags for dynamic libraries mentioned

  1354. on the command line after the <samp>--as-needed</samp> option.  Normally

  1355. the linker will add a DT_NEEDED tag for each dynamic library mentioned

  1356. on the command line, regardless of whether the library is actually

  1357. needed or not.  <samp>--as-needed</samp> causes a DT_NEEDED tag to only be

  1358. emitted for a library that <em>at that point in the link</em> satisfies a

  1359. non-weak undefined symbol reference from a regular object file or, if

  1360. the library is not found in the DT_NEEDED lists of other needed libraries, a

  1361. non-weak undefined symbol reference from another needed dynamic library.

  1362. Object files or libraries appearing on the command line <em>after</em>

  1363. the library in question do not affect whether the library is seen as

  1364. needed.  This is similar to the rules for extraction of object files

  1365. from archives.  <samp>--no-as-needed</samp> restores the default behaviour.

  1366. </p>

  1367. <a name="index-_002d_002dadd_002dneeded"></a>

  1368. <a name="index-_002d_002dno_002dadd_002dneeded"></a>

  1369. </dd>

  1370. <dt><code>--add-needed</code></dt>

  1371. <dt><code>--no-add-needed</code></dt>

  1372. <dd><p>These two options have been deprecated because of the similarity of

  1373. their names to the <samp>--as-needed</samp> and <samp>--no-as-needed</samp>

  1374. options.  They have been replaced by <samp>--copy-dt-needed-entries</samp>

  1375. and <samp>--no-copy-dt-needed-entries</samp>.

  1376. </p>

  1377. <a name="index-_002dassert-keyword"></a>

  1378. </dd>

  1379. <dt><code>-assert <var>keyword</var></code></dt>

  1380. <dd><p>This option is ignored for SunOS compatibility.

  1381. </p>

  1382. <a name="index-_002dBdynamic"></a>

  1383. <a name="index-_002ddy"></a>

  1384. <a name="index-_002dcall_005fshared"></a>

  1385. </dd>

  1386. <dt><code>-Bdynamic</code></dt>

  1387. <dt><code>-dy</code></dt>

  1388. <dt><code>-call_shared</code></dt>

  1389. <dd><p>Link against dynamic libraries.  This is only meaningful on platforms

  1390. for which shared libraries are supported.  This option is normally the

  1391. default on such platforms.  The different variants of this option are

  1392. for compatibility with various systems.  You may use this option

  1393. multiple times on the command line: it affects library searching for

  1394. <samp>-l</samp> options which follow it.

  1395. </p>

  1396. <a name="index-_002dBgroup"></a>

  1397. </dd>

  1398. <dt><code>-Bgroup</code></dt>

  1399. <dd><p>Set the <code>DF_1_GROUP</code> flag in the <code>DT_FLAGS_1</code> entry in the dynamic

  1400. section.  This causes the runtime linker to handle lookups in this

  1401. object and its dependencies to be performed only inside the group.

  1402. <samp>--unresolved-symbols=report-all</samp> is implied.  This option is

  1403. only meaningful on ELF platforms which support shared libraries.

  1404. </p>

  1405. <a name="index-_002dBstatic"></a>

  1406. <a name="index-_002ddn"></a>

  1407. <a name="index-_002dnon_005fshared"></a>

  1408. <a name="index-_002dstatic"></a>

  1409. </dd>

  1410. <dt><code>-Bstatic</code></dt>

  1411. <dt><code>-dn</code></dt>

  1412. <dt><code>-non_shared</code></dt>

  1413. <dt><code>-static</code></dt>

  1414. <dd><p>Do not link against shared libraries.  This is only meaningful on

  1415. platforms for which shared libraries are supported.  The different

  1416. variants of this option are for compatibility with various systems.  You

  1417. may use this option multiple times on the command line: it affects

  1418. library searching for <samp>-l</samp> options which follow it.  This

  1419. option also implies <samp>--unresolved-symbols=report-all</samp>.  This

  1420. option can be used with <samp>-shared</samp>.  Doing so means that a

  1421. shared library is being created but that all of the library&rsquo;s external

  1422. references must be resolved by pulling in entries from static

  1423. libraries.

  1424. </p>

  1425. <a name="index-_002dBsymbolic"></a>

  1426. </dd>

  1427. <dt><code>-Bsymbolic</code></dt>

  1428. <dd><p>When creating a shared library, bind references to global symbols to the

  1429. definition within the shared library, if any.  Normally, it is possible

  1430. for a program linked against a shared library to override the definition

  1431. within the shared library.  This option is only meaningful on ELF

  1432. platforms which support shared libraries.

  1433. </p>

  1434. <a name="index-_002dBsymbolic_002dfunctions"></a>

  1435. </dd>

  1436. <dt><code>-Bsymbolic-functions</code></dt>

  1437. <dd><p>When creating a shared library, bind references to global function

  1438. symbols to the definition within the shared library, if any.

  1439. This option is only meaningful on ELF platforms which support shared

  1440. libraries.

  1441. </p>

  1442. <a name="index-_002d_002ddynamic_002dlist_003ddynamic_002dlist_002dfile"></a>

  1443. </dd>

  1444. <dt><code>--dynamic-list=<var>dynamic-list-file</var></code></dt>

  1445. <dd><p>Specify the name of a dynamic list file to the linker.  This is

  1446. typically used when creating shared libraries to specify a list of

  1447. global symbols whose references shouldn&rsquo;t be bound to the definition

  1448. within the shared library, or creating dynamically linked executables

  1449. to specify a list of symbols which should be added to the symbol table

  1450. in the executable.  This option is only meaningful on ELF platforms

  1451. which support shared libraries.

  1452. </p>

  1453. <p>The format of the dynamic list is the same as the version node without

  1454. scope and node name.  See <a href="VERSION.html#VERSION">VERSION</a> for more information.

  1455. </p>

  1456. <a name="index-_002d_002ddynamic_002dlist_002ddata"></a>

  1457. </dd>

  1458. <dt><code>--dynamic-list-data</code></dt>

  1459. <dd><p>Include all global data symbols to the dynamic list.

  1460. </p>

  1461. <a name="index-_002d_002ddynamic_002dlist_002dcpp_002dnew"></a>

  1462. </dd>

  1463. <dt><code>--dynamic-list-cpp-new</code></dt>

  1464. <dd><p>Provide the builtin dynamic list for C++ operator new and delete.  It

  1465. is mainly useful for building shared libstdc++.

  1466. </p>

  1467. <a name="index-_002d_002ddynamic_002dlist_002dcpp_002dtypeinfo"></a>

  1468. </dd>

  1469. <dt><code>--dynamic-list-cpp-typeinfo</code></dt>

  1470. <dd><p>Provide the builtin dynamic list for C++ runtime type identification.

  1471. </p>

  1472. <a name="index-_002d_002dcheck_002dsections"></a>

  1473. <a name="index-_002d_002dno_002dcheck_002dsections"></a>

  1474. </dd>

  1475. <dt><code>--check-sections</code></dt>

  1476. <dt><code>--no-check-sections</code></dt>

  1477. <dd><p>Asks the linker <em>not</em> to check section addresses after they have

  1478. been assigned to see if there are any overlaps.  Normally the linker will

  1479. perform this check, and if it finds any overlaps it will produce

  1480. suitable error messages.  The linker does know about, and does make

  1481. allowances for sections in overlays.  The default behaviour can be

  1482. restored by using the command-line switch <samp>--check-sections</samp>.

  1483. Section overlap is not usually checked for relocatable links.  You can

  1484. force checking in that case by using the <samp>--check-sections</samp>

  1485. option.

  1486. </p>

  1487. <a name="index-_002d_002dcopy_002ddt_002dneeded_002dentries"></a>

  1488. <a name="index-_002d_002dno_002dcopy_002ddt_002dneeded_002dentries"></a>

  1489. </dd>

  1490. <dt><code>--copy-dt-needed-entries</code></dt>

  1491. <dt><code>--no-copy-dt-needed-entries</code></dt>

  1492. <dd><p>This option affects the treatment of dynamic libraries referred to

  1493. by DT_NEEDED tags <em>inside</em> ELF dynamic libraries mentioned on the

  1494. command line.  Normally the linker won&rsquo;t add a DT_NEEDED tag to the

  1495. output binary for each library mentioned in a DT_NEEDED tag in an

  1496. input dynamic library.  With <samp>--copy-dt-needed-entries</samp>

  1497. specified on the command line however any dynamic libraries that

  1498. follow it will have their DT_NEEDED entries added.  The default

  1499. behaviour can be restored with <samp>--no-copy-dt-needed-entries</samp>.

  1500. </p>

  1501. <p>This option also has an effect on the resolution of symbols in dynamic

  1502. libraries.  With <samp>--copy-dt-needed-entries</samp> dynamic libraries

  1503. mentioned on the command line will be recursively searched, following

  1504. their DT_NEEDED tags to other libraries, in order to resolve symbols

  1505. required by the output binary.  With the default setting however

  1506. the searching of dynamic libraries that follow it will stop with the

  1507. dynamic library itself.  No DT_NEEDED links will be traversed to resolve

  1508. symbols.

  1509. </p>

  1510. <a name="index-cross-reference-table"></a>

  1511. <a name="index-_002d_002dcref"></a>

  1512. </dd>

  1513. <dt><code>--cref</code></dt>

  1514. <dd><p>Output a cross reference table.  If a linker map file is being

  1515. generated, the cross reference table is printed to the map file.

  1516. Otherwise, it is printed on the standard output.

  1517. </p>

  1518. <p>The format of the table is intentionally simple, so that it may be

  1519. easily processed by a script if necessary.  The symbols are printed out,

  1520. sorted by name.  For each symbol, a list of file names is given.  If the

  1521. symbol is defined, the first file listed is the location of the

  1522. definition.  If the symbol is defined as a common value then any files

  1523. where this happens appear next.  Finally any files that reference the

  1524. symbol are listed.

  1525. </p>

  1526. <a name="index-common-allocation-1"></a>

  1527. <a name="index-_002d_002dno_002ddefine_002dcommon"></a>

  1528. </dd>

  1529. <dt><code>--no-define-common</code></dt>

  1530. <dd><p>This option inhibits the assignment of addresses to common symbols.

  1531. The script command <code>INHIBIT_COMMON_ALLOCATION</code> has the same effect.

  1532. See <a href="Miscellaneous-Commands.html#Miscellaneous-Commands">Miscellaneous Commands</a>.

  1533. </p>

  1534. <p>The &lsquo;<samp>--no-define-common</samp>&rsquo; option allows decoupling

  1535. the decision to assign addresses to Common symbols from the choice

  1536. of the output file type; otherwise a non-Relocatable output type

  1537. forces assigning addresses to Common symbols.

  1538. Using &lsquo;<samp>--no-define-common</samp>&rsquo; allows Common symbols that are referenced

  1539. from a shared library to be assigned addresses only in the main program.

  1540. This eliminates the unused duplicate space in the shared library,

  1541. and also prevents any possible confusion over resolving to the wrong

  1542. duplicate when there are many dynamic modules with specialized search

  1543. paths for runtime symbol resolution.

  1544. </p>

  1545. <a name="index-group-allocation-in-linker-script"></a>

  1546. <a name="index-section-groups"></a>

  1547. <a name="index-COMDAT"></a>

  1548. <a name="index-_002d_002dforce_002dgroup_002dallocation"></a>

  1549. </dd>

  1550. <dt><code>--force-group-allocation</code></dt>

  1551. <dd><p>This option causes the linker to place section group members like

  1552. normal input sections, and to delete the section groups.  This is the

  1553. default behaviour for a final link but this option can be used to

  1554. change the behaviour of a relocatable link (&lsquo;<samp>-r</samp>&rsquo;).  The script

  1555. command <code>FORCE_GROUP_ALLOCATION</code> has the same

  1556. effect. See <a href="Miscellaneous-Commands.html#Miscellaneous-Commands">Miscellaneous Commands</a>.

  1557. </p>

  1558. <a name="index-symbols_002c-from-command-line"></a>

  1559. <a name="index-_002d_002ddefsym_003dsymbol_003dexp"></a>

  1560. </dd>

  1561. <dt><code>--defsym=<var>symbol</var>=<var>expression</var></code></dt>

  1562. <dd><p>Create a global symbol in the output file, containing the absolute

  1563. address given by <var>expression</var>.  You may use this option as many

  1564. times as necessary to define multiple symbols in the command line.  A

  1565. limited form of arithmetic is supported for the <var>expression</var> in this

  1566. context: you may give a hexadecimal constant or the name of an existing

  1567. symbol, or use <code>+</code> and <code>-</code> to add or subtract hexadecimal

  1568. constants or symbols.  If you need more elaborate expressions, consider

  1569. using the linker command language from a script (see <a href="Assignments.html#Assignments">Assignments</a>).

  1570. <em>Note:</em> there should be no white space between <var>symbol</var>, the

  1571. equals sign (&ldquo;<tt class="key">=</tt>&rdquo;), and <var>expression</var>.

  1572. </p>

  1573. <a name="index-demangling_002c-from-command-line"></a>

  1574. <a name="index-_002d_002ddemangle_005b_003dstyle_005d"></a>

  1575. <a name="index-_002d_002dno_002ddemangle"></a>

  1576. </dd>

  1577. <dt><code>--demangle[=<var>style</var>]</code></dt>

  1578. <dt><code>--no-demangle</code></dt>

  1579. <dd><p>These options control whether to demangle symbol names in error messages

  1580. and other output.  When the linker is told to demangle, it tries to

  1581. present symbol names in a readable fashion: it strips leading

  1582. underscores if they are used by the object file format, and converts C++

  1583. mangled symbol names into user readable names.  Different compilers have

  1584. different mangling styles.  The optional demangling style argument can be used

  1585. to choose an appropriate demangling style for your compiler.  The linker will

  1586. demangle by default unless the environment variable &lsquo;<samp>COLLECT_NO_DEMANGLE</samp>&rsquo;

  1587. is set.  These options may be used to override the default.

  1588. </p>

  1589. <a name="index-dynamic-linker_002c-from-command-line"></a>

  1590. <a name="index-_002dIfile"></a>

  1591. <a name="index-_002d_002ddynamic_002dlinker_003dfile"></a>

  1592. </dd>

  1593. <dt><code>-I<var>file</var></code></dt>

  1594. <dt><code>--dynamic-linker=<var>file</var></code></dt>

  1595. <dd><p>Set the name of the dynamic linker.  This is only meaningful when

  1596. generating dynamically linked ELF executables.  The default dynamic

  1597. linker is normally correct; don&rsquo;t use this unless you know what you are

  1598. doing.

  1599. </p>

  1600. <a name="index-_002d_002dno_002ddynamic_002dlinker"></a>

  1601. </dd>

  1602. <dt><code>--no-dynamic-linker</code></dt>

  1603. <dd><p>When producing an executable file, omit the request for a dynamic

  1604. linker to be used at load-time.  This is only meaningful for ELF

  1605. executables that contain dynamic relocations, and usually requires

  1606. entry point code that is capable of processing these relocations.

  1607. </p>

  1608. <a name="index-_002d_002dembedded_002drelocs"></a>

  1609. </dd>

  1610. <dt><code>--embedded-relocs</code></dt>

  1611. <dd><p>This option is similar to the <samp>--emit-relocs</samp> option except

  1612. that the relocs are stored in a target-specific section.  This option

  1613. is only supported by the &lsquo;<samp>BFIN</samp>&rsquo;, &lsquo;<samp>CR16</samp>&rsquo; and <em>M68K</em>

  1614. targets.

  1615. </p>

  1616. <a name="index-_002d_002ddisable_002dmultiple_002dabs_002ddefs"></a>

  1617. </dd>

  1618. <dt><code>--disable-multiple-abs-defs</code></dt>

  1619. <dd><p>Do not allow multiple definitions with symbols included

  1620. in filename invoked by -R or &ndash;just-symbols

  1621. </p>

  1622. <a name="index-_002d_002dfatal_002dwarnings"></a>

  1623. <a name="index-_002d_002dno_002dfatal_002dwarnings"></a>

  1624. </dd>

  1625. <dt><code>--fatal-warnings</code></dt>

  1626. <dt><code>--no-fatal-warnings</code></dt>

  1627. <dd><p>Treat all warnings as errors.  The default behaviour can be restored

  1628. with the option <samp>--no-fatal-warnings</samp>.

  1629. </p>

  1630. <a name="index-_002d_002dforce_002dexe_002dsuffix"></a>

  1631. </dd>

  1632. <dt><code>--force-exe-suffix</code></dt>

  1633. <dd><p>Make sure that an output file has a .exe suffix.

  1634. </p>

  1635. <p>If a successfully built fully linked output file does not have a

  1636. <code>.exe</code> or <code>.dll</code> suffix, this option forces the linker to copy

  1637. the output file to one of the same name with a <code>.exe</code> suffix. This

  1638. option is useful when using unmodified Unix makefiles on a Microsoft

  1639. Windows host, since some versions of Windows won&rsquo;t run an image unless

  1640. it ends in a <code>.exe</code> suffix.

  1641. </p>

  1642. <a name="index-_002d_002dgc_002dsections"></a>

  1643. <a name="index-_002d_002dno_002dgc_002dsections"></a>

  1644. <a name="index-garbage-collection"></a>

  1645. </dd>

  1646. <dt><code>--gc-sections</code></dt>

  1647. <dt><code>--no-gc-sections</code></dt>

  1648. <dd><p>Enable garbage collection of unused input sections.  It is ignored on

  1649. targets that do not support this option.  The default behaviour (of not

  1650. performing this garbage collection) can be restored by specifying

  1651. &lsquo;<samp>--no-gc-sections</samp>&rsquo; on the command line.  Note that garbage

  1652. collection for COFF and PE format targets is supported, but the

  1653. implementation is currently considered to be experimental.

  1654. </p>

  1655. <p>&lsquo;<samp>--gc-sections</samp>&rsquo; decides which input sections are used by

  1656. examining symbols and relocations.  The section containing the entry

  1657. symbol and all sections containing symbols undefined on the

  1658. command-line will be kept, as will sections containing symbols

  1659. referenced by dynamic objects.  Note that when building shared

  1660. libraries, the linker must assume that any visible symbol is

  1661. referenced.  Once this initial set of sections has been determined,

  1662. the linker recursively marks as used any section referenced by their

  1663. relocations.  See &lsquo;<samp>--entry</samp>&rsquo;, &lsquo;<samp>--undefined</samp>&rsquo;, and

  1664. &lsquo;<samp>--gc-keep-exported</samp>&rsquo;.

  1665. </p>

  1666. <p>This option can be set when doing a partial link (enabled with option

  1667. &lsquo;<samp>-r</samp>&rsquo;).  In this case the root of symbols kept must be explicitly

  1668. specified either by one of the options &lsquo;<samp>--entry</samp>&rsquo;,

  1669. &lsquo;<samp>--undefined</samp>&rsquo;, or &lsquo;<samp>--gc-keep-exported</samp>&rsquo; or by a <code>ENTRY</code>

  1670. command in the linker script.

  1671. </p>

  1672. <a name="index-_002d_002dprint_002dgc_002dsections"></a>

  1673. <a name="index-_002d_002dno_002dprint_002dgc_002dsections"></a>

  1674. <a name="index-garbage-collection-1"></a>

  1675. </dd>

  1676. <dt><code>--print-gc-sections</code></dt>

  1677. <dt><code>--no-print-gc-sections</code></dt>

  1678. <dd><p>List all sections removed by garbage collection.  The listing is

  1679. printed on stderr.  This option is only effective if garbage

  1680. collection has been enabled via the &lsquo;<samp>--gc-sections</samp>&rsquo;) option.  The

  1681. default behaviour (of not listing the sections that are removed) can

  1682. be restored by specifying &lsquo;<samp>--no-print-gc-sections</samp>&rsquo; on the command

  1683. line.

  1684. </p>

  1685. <a name="index-_002d_002dgc_002dkeep_002dexported"></a>

  1686. <a name="index-garbage-collection-2"></a>

  1687. </dd>

  1688. <dt><code>--gc-keep-exported</code></dt>

  1689. <dd><p>When &lsquo;<samp>--gc-sections</samp>&rsquo; is enabled, this option prevents garbage

  1690. collection of unused input sections that contain global symbols having

  1691. default or protected visibility.  This option is intended to be used for

  1692. executables where unreferenced sections would otherwise be garbage

  1693. collected regardless of the external visibility of contained symbols.

  1694. Note that this option has no effect when linking shared objects since

  1695. it is already the default behaviour.  This option is only supported for

  1696. ELF format targets.

  1697. </p>

  1698. <a name="index-_002d_002dprint_002doutput_002dformat"></a>

  1699. <a name="index-output-format"></a>

  1700. </dd>

  1701. <dt><code>--print-output-format</code></dt>

  1702. <dd><p>Print the name of the default output format (perhaps influenced by

  1703. other command-line options).  This is the string that would appear

  1704. in an <code>OUTPUT_FORMAT</code> linker script command (see <a href="File-Commands.html#File-Commands">File Commands</a>).

  1705. </p>

  1706. <a name="index-_002d_002dprint_002dmemory_002dusage"></a>

  1707. <a name="index-memory-usage"></a>

  1708. </dd>

  1709. <dt><code>--print-memory-usage</code></dt>

  1710. <dd><p>Print used size, total size and used size of memory regions created with

  1711. the <a href="MEMORY.html#MEMORY">MEMORY</a> command.  This is useful on embedded targets to have a

  1712. quick view of amount of free memory.  The format of the output has one

  1713. headline and one line per region.  It is both human readable and easily

  1714. parsable by tools.  Here is an example of an output:

  1715. </p>

  1716. <div class="smallexample">

  1717. <pre class="smallexample">Memory region         Used Size  Region Size  %age Used

  1718.              ROM:        256 KB         1 MB     25.00%

  1719.              RAM:          32 B         2 GB      0.00%

  1720. </pre></div>

  1721. 

  1722. <a name="index-help"></a>

  1723. <a name="index-usage"></a>

  1724. <a name="index-_002d_002dhelp"></a>

  1725. </dd>

  1726. <dt><code>--help</code></dt>

  1727. <dd><p>Print a summary of the command-line options on the standard output and exit.

  1728. </p>

  1729. <a name="index-_002d_002dtarget_002dhelp"></a>

  1730. </dd>

  1731. <dt><code>--target-help</code></dt>

  1732. <dd><p>Print a summary of all target-specific options on the standard output and exit.

  1733. </p>

  1734. <a name="index-_002dMap_003dmapfile"></a>

  1735. </dd>

  1736. <dt><code>-Map=<var>mapfile</var></code></dt>

  1737. <dd><p>Print a link map to the file <var>mapfile</var>.  See the description of the

  1738. <samp>-M</samp> option, above.  Specifying a directory as <var>mapfile</var>

  1739. causes the linker map to be written into a file inside the directory.

  1740. The name of the file is based upon the <var>output</var> filename with

  1741. <code>.map</code> appended.

  1742. </p>

  1743. <a name="index-memory-usage-1"></a>

  1744. <a name="index-_002d_002dno_002dkeep_002dmemory"></a>

  1745. </dd>

  1746. <dt><code>--no-keep-memory</code></dt>

  1747. <dd><p><code>ld</code> normally optimizes for speed over memory usage by caching the

  1748. symbol tables of input files in memory.  This option tells <code>ld</code> to

  1749. instead optimize for memory usage, by rereading the symbol tables as

  1750. necessary.  This may be required if <code>ld</code> runs out of memory space

  1751. while linking a large executable.

  1752. </p>

  1753. <a name="index-_002d_002dno_002dundefined"></a>

  1754. <a name="index-_002dz-defs"></a>

  1755. <a name="index-_002dz-undefs"></a>

  1756. </dd>

  1757. <dt><code>--no-undefined</code></dt>

  1758. <dt><code>-z defs</code></dt>

  1759. <dd><p>Report unresolved symbol references from regular object files.  This

  1760. is done even if the linker is creating a non-symbolic shared library.

  1761. The switch <samp>--[no-]allow-shlib-undefined</samp> controls the

  1762. behaviour for reporting unresolved references found in shared

  1763. libraries being linked in.

  1764. </p>

  1765. <p>The effects of this option can be reverted by using <code>-z undefs</code>.

  1766. </p>

  1767. <a name="index-_002d_002dallow_002dmultiple_002ddefinition"></a>

  1768. <a name="index-_002dz-muldefs"></a>

  1769. </dd>

  1770. <dt><code>--allow-multiple-definition</code></dt>

  1771. <dt><code>-z muldefs</code></dt>

  1772. <dd><p>Normally when a symbol is defined multiple times, the linker will

  1773. report a fatal error. These options allow multiple definitions and the

  1774. first definition will be used.

  1775. </p>

  1776. <a name="index-_002d_002dallow_002dshlib_002dundefined"></a>

  1777. <a name="index-_002d_002dno_002dallow_002dshlib_002dundefined"></a>

  1778. </dd>

  1779. <dt><code>--allow-shlib-undefined</code></dt>

  1780. <dt><code>--no-allow-shlib-undefined</code></dt>

  1781. <dd><p>Allows or disallows undefined symbols in shared libraries.

  1782. This switch is similar to <samp>--no-undefined</samp> except that it

  1783. determines the behaviour when the undefined symbols are in a

  1784. shared library rather than a regular object file.  It does not affect

  1785. how undefined symbols in regular object files are handled.

  1786. </p>

  1787. <p>The default behaviour is to report errors for any undefined symbols

  1788. referenced in shared libraries if the linker is being used to create

  1789. an executable, but to allow them if the linker is being used to create

  1790. a shared library.

  1791. </p>

  1792. <p>The reasons for allowing undefined symbol references in shared

  1793. libraries specified at link time are that:

  1794. </p>

  1795. <ul>

  1796. <li> A shared library specified at link time may not be the same as the one

  1797. that is available at load time, so the symbol might actually be

  1798. resolvable at load time.

  1799. </li><li> There are some operating systems, eg BeOS and HPPA, where undefined

  1800. symbols in shared libraries are normal.

  1801. 

  1802. <p>The BeOS kernel for example patches shared libraries at load time to

  1803. select whichever function is most appropriate for the current

  1804. architecture.  This is used, for example, to dynamically select an

  1805. appropriate memset function.

  1806. </p></li></ul>

  1807. 

  1808. <a name="index-_002d_002dno_002dundefined_002dversion"></a>

  1809. </dd>

  1810. <dt><code>--no-undefined-version</code></dt>

  1811. <dd><p>Normally when a symbol has an undefined version, the linker will ignore

  1812. it. This option disallows symbols with undefined version and a fatal error

  1813. will be issued instead.

  1814. </p>

  1815. <a name="index-_002d_002ddefault_002dsymver"></a>

  1816. </dd>

  1817. <dt><code>--default-symver</code></dt>

  1818. <dd><p>Create and use a default symbol version (the soname) for unversioned

  1819. exported symbols.

  1820. </p>

  1821. <a name="index-_002d_002ddefault_002dimported_002dsymver"></a>

  1822. </dd>

  1823. <dt><code>--default-imported-symver</code></dt>

  1824. <dd><p>Create and use a default symbol version (the soname) for unversioned

  1825. imported symbols.

  1826. </p>

  1827. <a name="index-_002d_002dno_002dwarn_002dmismatch"></a>

  1828. </dd>

  1829. <dt><code>--no-warn-mismatch</code></dt>

  1830. <dd><p>Normally <code>ld</code> will give an error if you try to link together input

  1831. files that are mismatched for some reason, perhaps because they have

  1832. been compiled for different processors or for different endiannesses.

  1833. This option tells <code>ld</code> that it should silently permit such possible

  1834. errors.  This option should only be used with care, in cases when you

  1835. have taken some special action that ensures that the linker errors are

  1836. inappropriate.

  1837. </p>

  1838. <a name="index-_002d_002dno_002dwarn_002dsearch_002dmismatch"></a>

  1839. </dd>

  1840. <dt><code>--no-warn-search-mismatch</code></dt>

  1841. <dd><p>Normally <code>ld</code> will give a warning if it finds an incompatible

  1842. library during a library search.  This option silences the warning.

  1843. </p>

  1844. <a name="index-_002d_002dno_002dwhole_002darchive"></a>

  1845. </dd>

  1846. <dt><code>--no-whole-archive</code></dt>

  1847. <dd><p>Turn off the effect of the <samp>--whole-archive</samp> option for subsequent

  1848. archive files.

  1849. </p>

  1850. <a name="index-output-file-after-errors"></a>

  1851. <a name="index-_002d_002dnoinhibit_002dexec"></a>

  1852. </dd>

  1853. <dt><code>--noinhibit-exec</code></dt>

  1854. <dd><p>Retain the executable output file whenever it is still usable.

  1855. Normally, the linker will not produce an output file if it encounters

  1856. errors during the link process; it exits without writing an output file

  1857. when it issues any error whatsoever.

  1858. </p>

  1859. <a name="index-_002dnostdlib"></a>

  1860. </dd>

  1861. <dt><code>-nostdlib</code></dt>

  1862. <dd><p>Only search library directories explicitly specified on the

  1863. command line.  Library directories specified in linker scripts

  1864. (including linker scripts specified on the command line) are ignored.

  1865. </p>

  1866. <a name="index-_002d_002doformat_003doutput_002dformat"></a>

  1867. </dd>

  1868. <dt><code>--oformat=<var>output-format</var></code></dt>

  1869. <dd><p><code>ld</code> may be configured to support more than one kind of object

  1870. file.  If your <code>ld</code> is configured this way, you can use the

  1871. &lsquo;<samp>--oformat</samp>&rsquo; option to specify the binary format for the output

  1872. object file.  Even when <code>ld</code> is configured to support alternative

  1873. object formats, you don&rsquo;t usually need to specify this, as <code>ld</code>

  1874. should be configured to produce as a default output format the most

  1875. usual format on each machine.  <var>output-format</var> is a text string, the

  1876. name of a particular format supported by the BFD libraries.  (You can

  1877. list the available binary formats with &lsquo;<samp>objdump -i</samp>&rsquo;.)  The script

  1878. command <code>OUTPUT_FORMAT</code> can also specify the output format, but

  1879. this option overrides it.  See <a href="BFD.html#BFD">BFD</a>.

  1880. </p>

  1881. <a name="index-_002d_002dout_002dimplib"></a>

  1882. </dd>

  1883. <dt><code>--out-implib <var>file</var></code></dt>

  1884. <dd><p>Create an import library in <var>file</var> corresponding to the executable

  1885. the linker is generating (eg. a DLL or ELF program).  This import

  1886. library (which should be called <code>*.dll.a</code> or <code>*.a</code> for DLLs)

  1887. may be used to link clients against the generated executable; this

  1888. behaviour makes it possible to skip a separate import library creation

  1889. step (eg. <code>dlltool</code> for DLLs).  This option is only available for

  1890. the i386 PE and ELF targetted ports of the linker.

  1891. </p>

  1892. <a name="index-_002dpie"></a>

  1893. <a name="index-_002d_002dpic_002dexecutable"></a>

  1894. </dd>

  1895. <dt><code>-pie</code></dt>

  1896. <dt><code>--pic-executable</code></dt>

  1897. <dd><a name="index-position-independent-executables"></a>

  1898. <p>Create a position independent executable.  This is currently only supported on

  1899. ELF platforms.  Position independent executables are similar to shared

  1900. libraries in that they are relocated by the dynamic linker to the virtual

  1901. address the OS chooses for them (which can vary between invocations).  Like

  1902. normal dynamically linked executables they can be executed and symbols

  1903. defined in the executable cannot be overridden by shared libraries.

  1904. </p>

  1905. <a name="index-_002dqmagic"></a>

  1906. </dd>

  1907. <dt><code>-qmagic</code></dt>

  1908. <dd><p>This option is ignored for Linux compatibility.

  1909. </p>

  1910. <a name="index-_002dQy"></a>

  1911. </dd>

  1912. <dt><code>-Qy</code></dt>

  1913. <dd><p>This option is ignored for SVR4 compatibility.

  1914. </p>

  1915. <a name="index-_002d_002drelax"></a>

  1916. <a name="index-synthesizing-linker"></a>

  1917. <a name="index-relaxing-addressing-modes"></a>

  1918. <a name="index-_002d_002dno_002drelax"></a>

  1919. </dd>

  1920. <dt><code>--relax</code></dt>

  1921. <dt><code>--no-relax</code></dt>

  1922. <dd><p>An option with machine dependent effects.

  1923. This option is only supported on a few targets.

  1924. See <a href="H8_002f300.html#H8_002f300"><code>ld</code> and the H8/300</a>.

  1925. See <a href="Xtensa.html#Xtensa"><code>ld</code> and Xtensa Processors</a>.

  1926. See <a href="M68HC11_002f68HC12.html#M68HC11_002f68HC12"><code>ld</code> and the 68HC11 and 68HC12</a>.

  1927. See <a href="Nios-II.html#Nios-II"><code>ld</code> and the Altera Nios II</a>.

  1928. See <a href="PowerPC-ELF32.html#PowerPC-ELF32"><code>ld</code> and PowerPC 32-bit ELF Support</a>.

  1929. </p>

  1930. <p>On some platforms the &lsquo;<samp>--relax</samp>&rsquo; option performs target-specific,

  1931. global optimizations that become possible when the linker resolves

  1932. addressing in the program, such as relaxing address modes,

  1933. synthesizing new instructions, selecting shorter version of current

  1934. instructions, and combining constant values.

  1935. </p>

  1936. <p>On some platforms these link time global optimizations may make symbolic

  1937. debugging of the resulting executable impossible.

  1938. This is known to be the case for the Matsushita MN10200 and MN10300

  1939. family of processors.

  1940. </p>

  1941. <p>On platforms where this is not supported, &lsquo;<samp>--relax</samp>&rsquo; is accepted,

  1942. but ignored.

  1943. </p>

  1944. <p>On platforms where &lsquo;<samp>--relax</samp>&rsquo; is accepted the option

  1945. &lsquo;<samp>--no-relax</samp>&rsquo; can be used to disable the feature.

  1946. </p>

  1947. <a name="index-retaining-specified-symbols"></a>

  1948. <a name="index-stripping-all-but-some-symbols"></a>

  1949. <a name="index-symbols_002c-retaining-selectively"></a>

  1950. <a name="index-_002d_002dretain_002dsymbols_002dfile_003dfilename"></a>

  1951. </dd>

  1952. <dt><code>--retain-symbols-file=<var>filename</var></code></dt>

  1953. <dd><p>Retain <em>only</em> the symbols listed in the file <var>filename</var>,

  1954. discarding all others.  <var>filename</var> is simply a flat file, with one

  1955. symbol name per line.  This option is especially useful in environments

  1956. (such as VxWorks)

  1957. where a large global symbol table is accumulated gradually, to conserve

  1958. run-time memory.

  1959. </p>

  1960. <p>&lsquo;<samp>--retain-symbols-file</samp>&rsquo; does <em>not</em> discard undefined symbols,

  1961. or symbols needed for relocations.

  1962. </p>

  1963. <p>You may only specify &lsquo;<samp>--retain-symbols-file</samp>&rsquo; once in the command

  1964. line.  It overrides &lsquo;<samp>-s</samp>&rsquo; and &lsquo;<samp>-S</samp>&rsquo;.

  1965. </p>

  1966. </dd>

  1967. <dt><code>-rpath=<var>dir</var></code></dt>

  1968. <dd><a name="index-runtime-library-search-path"></a>

  1969. <a name="index-_002drpath_003ddir"></a>

  1970. <p>Add a directory to the runtime library search path.  This is used when

  1971. linking an ELF executable with shared objects.  All <samp>-rpath</samp>

  1972. arguments are concatenated and passed to the runtime linker, which uses

  1973. them to locate shared objects at runtime.

  1974. </p>

  1975. <p>The <samp>-rpath</samp> option is also used when locating shared objects which

  1976. are needed by shared objects explicitly included in the link; see the

  1977. description of the <samp>-rpath-link</samp> option.  Searching <samp>-rpath</samp>

  1978. in this way is only supported by native linkers and cross linkers which

  1979. have been configured with the <samp>--with-sysroot</samp> option.

  1980. </p>

  1981. <p>If <samp>-rpath</samp> is not used when linking an ELF executable, the

  1982. contents of the environment variable <code>LD_RUN_PATH</code> will be used if it

  1983. is defined.

  1984. </p>

  1985. <p>The <samp>-rpath</samp> option may also be used on SunOS.  By default, on

  1986. SunOS, the linker will form a runtime search path out of all the

  1987. <samp>-L</samp> options it is given.  If a <samp>-rpath</samp> option is used, the

  1988. runtime search path will be formed exclusively using the <samp>-rpath</samp>

  1989. options, ignoring the <samp>-L</samp> options.  This can be useful when using

  1990. gcc, which adds many <samp>-L</samp> options which may be on NFS mounted

  1991. file systems.

  1992. </p>

  1993. <p>For compatibility with other ELF linkers, if the <samp>-R</samp> option is

  1994. followed by a directory name, rather than a file name, it is treated as

  1995. the <samp>-rpath</samp> option.

  1996. </p>

  1997. <a name="index-link_002dtime-runtime-library-search-path"></a>

  1998. <a name="index-_002drpath_002dlink_003ddir"></a>

  1999. </dd>

  2000. <dt><code>-rpath-link=<var>dir</var></code></dt>

  2001. <dd><p>When using ELF or SunOS, one shared library may require another.  This

  2002. happens when an <code>ld -shared</code> link includes a shared library as one

  2003. of the input files.

  2004. </p>

  2005. <p>When the linker encounters such a dependency when doing a non-shared,

  2006. non-relocatable link, it will automatically try to locate the required

  2007. shared library and include it in the link, if it is not included

  2008. explicitly.  In such a case, the <samp>-rpath-link</samp> option

  2009. specifies the first set of directories to search.  The

  2010. <samp>-rpath-link</samp> option may specify a sequence of directory names

  2011. either by specifying a list of names separated by colons, or by

  2012. appearing multiple times.

  2013. </p>

  2014. <p>The tokens <var>$ORIGIN</var> and <var>$LIB</var> can appear in these search

  2015. directories.  They will be replaced by the full path to the directory

  2016. containing the program or shared object in the case of <var>$ORIGIN</var>

  2017. and either &lsquo;<samp>lib</samp>&rsquo; - for 32-bit binaries - or &lsquo;<samp>lib64</samp>&rsquo; - for

  2018. 64-bit binaries - in the case of <var>$LIB</var>.

  2019. </p>

  2020. <p>The alternative form of these tokens - <var>${ORIGIN}</var> and

  2021. <var>${LIB}</var> can also be used.  The token <var>$PLATFORM</var> is not

  2022. supported.

  2023. </p>

  2024. <p>This option should be used with caution as it overrides the search path

  2025. that may have been hard compiled into a shared library. In such a case it

  2026. is possible to use unintentionally a different search path than the

  2027. runtime linker would do.

  2028. </p>

  2029. <p>The linker uses the following search paths to locate required shared

  2030. libraries:

  2031. </p>

  2032. <ol>

  2033. <li> Any directories specified by <samp>-rpath-link</samp> options.

  2034. </li><li> Any directories specified by <samp>-rpath</samp> options.  The difference

  2035. between <samp>-rpath</samp> and <samp>-rpath-link</samp> is that directories

  2036. specified by <samp>-rpath</samp> options are included in the executable and

  2037. used at runtime, whereas the <samp>-rpath-link</samp> option is only effective

  2038. at link time. Searching <samp>-rpath</samp> in this way is only supported

  2039. by native linkers and cross linkers which have been configured with

  2040. the <samp>--with-sysroot</samp> option.

  2041. </li><li> On an ELF system, for native linkers, if the <samp>-rpath</samp> and

  2042. <samp>-rpath-link</samp> options were not used, search the contents of the

  2043. environment variable <code>LD_RUN_PATH</code>.

  2044. </li><li> On SunOS, if the <samp>-rpath</samp> option was not used, search any

  2045. directories specified using <samp>-L</samp> options.

  2046. </li><li> For a native linker, search the contents of the environment

  2047. variable <code>LD_LIBRARY_PATH</code>.

  2048. </li><li> For a native ELF linker, the directories in <code>DT_RUNPATH</code> or

  2049. <code>DT_RPATH</code> of a shared library are searched for shared

  2050. libraries needed by it. The <code>DT_RPATH</code> entries are ignored if

  2051. <code>DT_RUNPATH</code> entries exist.

  2052. </li><li> The default directories, normally <samp>/lib</samp> and <samp>/usr/lib</samp>.

  2053. </li><li> For a linker for a Linux system, if the file <samp>/etc/ld.so.conf</samp>

  2054. exists, the list of directories found in that file.  Note: the path

  2055. to this file is prefixed with the <code>sysroot</code> value, if that is

  2056. defined, and then any <code>prefix</code> string if the linker was

  2057. configured with the <code>--prefix=&lt;path&gt;</code> option.

  2058. </li><li> For a native linker on a FreeBSD system, any directories specified by

  2059. the <code>_PATH_ELF_HINTS</code> macro defined in the <samp>elf-hints.h</samp>

  2060. header file.

  2061. </li><li> Any directories specifed by a <code>SEARCH_DIR</code> command in the

  2062. linker script being used.

  2063. </li></ol>

  2064. 

  2065. <p>If the required shared library is not found, the linker will issue a

  2066. warning and continue with the link.

  2067. </p>

  2068. <a name="index-_002dshared"></a>

  2069. <a name="index-_002dBshareable"></a>

  2070. </dd>

  2071. <dt><code>-shared</code></dt>

  2072. <dt><code>-Bshareable</code></dt>

  2073. <dd><a name="index-shared-libraries"></a>

  2074. <p>Create a shared library.  This is currently only supported on ELF, XCOFF

  2075. and SunOS platforms.  On SunOS, the linker will automatically create a

  2076. shared library if the <samp>-e</samp> option is not used and there are

  2077. undefined symbols in the link.

  2078. </p>

  2079. <a name="index-_002d_002dsort_002dcommon"></a>

  2080. </dd>

  2081. <dt><code>--sort-common</code></dt>

  2082. <dt><code>--sort-common=ascending</code></dt>

  2083. <dt><code>--sort-common=descending</code></dt>

  2084. <dd><p>This option tells <code>ld</code> to sort the common symbols by alignment in

  2085. ascending or descending order when it places them in the appropriate output

  2086. sections.  The symbol alignments considered are sixteen-byte or larger,

  2087. eight-byte, four-byte, two-byte, and one-byte. This is to prevent gaps

  2088. between symbols due to alignment constraints.  If no sorting order is

  2089. specified, then descending order is assumed.

  2090. </p>

  2091. <a name="index-_002d_002dsort_002dsection_003dname"></a>

  2092. </dd>

  2093. <dt><code>--sort-section=name</code></dt>

  2094. <dd><p>This option will apply <code>SORT_BY_NAME</code> to all wildcard section

  2095. patterns in the linker script.

  2096. </p>

  2097. <a name="index-_002d_002dsort_002dsection_003dalignment"></a>

  2098. </dd>

  2099. <dt><code>--sort-section=alignment</code></dt>

  2100. <dd><p>This option will apply <code>SORT_BY_ALIGNMENT</code> to all wildcard section

  2101. patterns in the linker script.

  2102. </p>

  2103. <a name="index-_002d_002dspare_002ddynamic_002dtags"></a>

  2104. </dd>

  2105. <dt><code>--spare-dynamic-tags=<var>count</var></code></dt>

  2106. <dd><p>This option specifies the number of empty slots to leave in the

  2107. .dynamic section of ELF shared objects.  Empty slots may be needed by

  2108. post processing tools, such as the prelinker.  The default is 5.

  2109. </p>

  2110. <a name="index-_002d_002dsplit_002dby_002dfile"></a>

  2111. </dd>

  2112. <dt><code>--split-by-file[=<var>size</var>]</code></dt>

  2113. <dd><p>Similar to <samp>--split-by-reloc</samp> but creates a new output section for

  2114. each input file when <var>size</var> is reached.  <var>size</var> defaults to a

  2115. size of 1 if not given.

  2116. </p>

  2117. <a name="index-_002d_002dsplit_002dby_002dreloc"></a>

  2118. </dd>

  2119. <dt><code>--split-by-reloc[=<var>count</var>]</code></dt>

  2120. <dd><p>Tries to creates extra sections in the output file so that no single

  2121. output section in the file contains more than <var>count</var> relocations.

  2122. This is useful when generating huge relocatable files for downloading into

  2123. certain real time kernels with the COFF object file format; since COFF

  2124. cannot represent more than 65535 relocations in a single section.  Note

  2125. that this will fail to work with object file formats which do not

  2126. support arbitrary sections.  The linker will not split up individual

  2127. input sections for redistribution, so if a single input section contains

  2128. more than <var>count</var> relocations one output section will contain that

  2129. many relocations.  <var>count</var> defaults to a value of 32768.

  2130. </p>

  2131. <a name="index-_002d_002dstats"></a>

  2132. </dd>

  2133. <dt><code>--stats</code></dt>

  2134. <dd><p>Compute and display statistics about the operation of the linker, such

  2135. as execution time and memory usage.

  2136. </p>

  2137. <a name="index-_002d_002dsysroot_003ddirectory"></a>

  2138. </dd>

  2139. <dt><code>--sysroot=<var>directory</var></code></dt>

  2140. <dd><p>Use <var>directory</var> as the location of the sysroot, overriding the

  2141. configure-time default.  This option is only supported by linkers

  2142. that were configured using <samp>--with-sysroot</samp>.

  2143. </p>

  2144. <a name="index-_002d_002dtask_002dlink"></a>

  2145. </dd>

  2146. <dt><code>--task-link</code></dt>

  2147. <dd><p>This is used by COFF/PE based targets to create a task-linked object

  2148. file where all of the global symbols have been converted to statics.

  2149. </p>

  2150. <a name="index-_002d_002dtraditional_002dformat"></a>

  2151. <a name="index-traditional-format"></a>

  2152. </dd>

  2153. <dt><code>--traditional-format</code></dt>

  2154. <dd><p>For some targets, the output of <code>ld</code> is different in some ways from

  2155. the output of some existing linker.  This switch requests <code>ld</code> to

  2156. use the traditional format instead.

  2157. </p>

  2158. <a name="index-dbx"></a>

  2159. <p>For example, on SunOS, <code>ld</code> combines duplicate entries in the

  2160. symbol string table.  This can reduce the size of an output file with

  2161. full debugging information by over 30 percent.  Unfortunately, the SunOS

  2162. <code>dbx</code> program can not read the resulting program (<code>gdb</code> has no

  2163. trouble).  The &lsquo;<samp>--traditional-format</samp>&rsquo; switch tells <code>ld</code> to not

  2164. combine duplicate entries.

  2165. </p>

  2166. <a name="index-_002d_002dsection_002dstart_003dsectionname_003dorg"></a>

  2167. </dd>

  2168. <dt><code>--section-start=<var>sectionname</var>=<var>org</var></code></dt>

  2169. <dd><p>Locate a section in the output file at the absolute

  2170. address given by <var>org</var>.  You may use this option as many

  2171. times as necessary to locate multiple sections in the command

  2172. line.

  2173. <var>org</var> must be a single hexadecimal integer;

  2174. for compatibility with other linkers, you may omit the leading

  2175. &lsquo;<samp>0x</samp>&rsquo; usually associated with hexadecimal values.  <em>Note:</em> there

  2176. should be no white space between <var>sectionname</var>, the equals

  2177. sign (&ldquo;<tt class="key">=</tt>&rdquo;), and <var>org</var>.

  2178. </p>

  2179. <a name="index-_002dTbss_003dorg"></a>

  2180. <a name="index-_002dTdata_003dorg"></a>

  2181. <a name="index-_002dTtext_003dorg"></a>

  2182. <a name="index-segment-origins_002c-cmd-line"></a>

  2183. </dd>

  2184. <dt><code>-Tbss=<var>org</var></code></dt>

  2185. <dt><code>-Tdata=<var>org</var></code></dt>

  2186. <dt><code>-Ttext=<var>org</var></code></dt>

  2187. <dd><p>Same as <samp>--section-start</samp>, with <code>.bss</code>, <code>.data</code> or

  2188. <code>.text</code> as the <var>sectionname</var>.

  2189. </p>

  2190. <a name="index-_002dTtext_002dsegment_003dorg"></a>

  2191. </dd>

  2192. <dt><code>-Ttext-segment=<var>org</var></code></dt>

  2193. <dd><a name="index-text-segment-origin_002c-cmd-line"></a>

  2194. <p>When creating an ELF executable, it will set the address of the first

  2195. byte of the text segment.

  2196. </p>

  2197. <a name="index-_002dTrodata_002dsegment_003dorg"></a>

  2198. </dd>

  2199. <dt><code>-Trodata-segment=<var>org</var></code></dt>

  2200. <dd><a name="index-rodata-segment-origin_002c-cmd-line"></a>

  2201. <p>When creating an ELF executable or shared object for a target where

  2202. the read-only data is in its own segment separate from the executable

  2203. text, it will set the address of the first byte of the read-only data segment.

  2204. </p>

  2205. <a name="index-_002dTldata_002dsegment_003dorg"></a>

  2206. </dd>

  2207. <dt><code>-Tldata-segment=<var>org</var></code></dt>

  2208. <dd><a name="index-ldata-segment-origin_002c-cmd-line"></a>

  2209. <p>When creating an ELF executable or shared object for x86-64 medium memory

  2210. model, it will set the address of the first byte of the ldata segment.

  2211. </p>

  2212. <a name="index-_002d_002dunresolved_002dsymbols"></a>

  2213. </dd>

  2214. <dt><code>--unresolved-symbols=<var>method</var></code></dt>

  2215. <dd><p>Determine how to handle unresolved symbols.  There are four possible

  2216. values for &lsquo;<samp>method</samp>&rsquo;:

  2217. </p>

  2218. <dl compact="compact">

  2219. <dt>&lsquo;<samp>ignore-all</samp>&rsquo;</dt>

  2220. <dd><p>Do not report any unresolved symbols.

  2221. </p>

  2222. </dd>

  2223. <dt>&lsquo;<samp>report-all</samp>&rsquo;</dt>

  2224. <dd><p>Report all unresolved symbols.  This is the default.

  2225. </p>

  2226. </dd>

  2227. <dt>&lsquo;<samp>ignore-in-object-files</samp>&rsquo;</dt>

  2228. <dd><p>Report unresolved symbols that are contained in shared libraries, but

  2229. ignore them if they come from regular object files.

  2230. </p>

  2231. </dd>

  2232. <dt>&lsquo;<samp>ignore-in-shared-libs</samp>&rsquo;</dt>

  2233. <dd><p>Report unresolved symbols that come from regular object files, but

  2234. ignore them if they come from shared libraries.  This can be useful

  2235. when creating a dynamic binary and it is known that all the shared

  2236. libraries that it should be referencing are included on the linker&rsquo;s

  2237. command line.

  2238. </p></dd>

  2239. </dl>

  2240. 

  2241. <p>The behaviour for shared libraries on their own can also be controlled

  2242. by the <samp>--[no-]allow-shlib-undefined</samp> option.

  2243. </p>

  2244. <p>Normally the linker will generate an error message for each reported

  2245. unresolved symbol but the option <samp>--warn-unresolved-symbols</samp>

  2246. can change this to a warning.

  2247. </p>

  2248. <a name="index-_002d_002dverbose_005b_003dNUMBER_005d"></a>

  2249. <a name="index-verbose_005b_003dNUMBER_005d"></a>

  2250. </dd>

  2251. <dt><code>--dll-verbose</code></dt>

  2252. <dt><code>--verbose[=<var>NUMBER</var>]</code></dt>

  2253. <dd><p>Display the version number for <code>ld</code> and list the linker emulations

  2254. supported.  Display which input files can and cannot be opened.  Display

  2255. the linker script being used by the linker. If the optional <var>NUMBER</var>

  2256. argument &gt; 1, plugin symbol status will also be displayed.

  2257. </p>

  2258. <a name="index-_002d_002dversion_002dscript_003dversion_002dscriptfile"></a>

  2259. <a name="index-version-script_002c-symbol-versions"></a>

  2260. </dd>

  2261. <dt><code>--version-script=<var>version-scriptfile</var></code></dt>

  2262. <dd><p>Specify the name of a version script to the linker.  This is typically

  2263. used when creating shared libraries to specify additional information

  2264. about the version hierarchy for the library being created.  This option

  2265. is only fully supported on ELF platforms which support shared libraries;

  2266. see <a href="VERSION.html#VERSION">VERSION</a>.  It is partially supported on PE platforms, which can

  2267. use version scripts to filter symbol visibility in auto-export mode: any

  2268. symbols marked &lsquo;<samp>local</samp>&rsquo; in the version script will not be exported.

  2269. See <a href="WIN32.html#WIN32">WIN32</a>.

  2270. </p>

  2271. <a name="index-_002d_002dwarn_002dcommon"></a>

  2272. <a name="index-warnings_002c-on-combining-symbols"></a>

  2273. <a name="index-combining-symbols_002c-warnings-on"></a>

  2274. </dd>

  2275. <dt><code>--warn-common</code></dt>

  2276. <dd><p>Warn when a common symbol is combined with another common symbol or with

  2277. a symbol definition.  Unix linkers allow this somewhat sloppy practice,

  2278. but linkers on some other operating systems do not.  This option allows

  2279. you to find potential problems from combining global symbols.

  2280. Unfortunately, some C libraries use this practice, so you may get some

  2281. warnings about symbols in the libraries as well as in your programs.

  2282. </p>

  2283. <p>There are three kinds of global symbols, illustrated here by C examples:

  2284. </p>

  2285. <dl compact="compact">

  2286. <dt>&lsquo;<samp>int i = 1;</samp>&rsquo;</dt>

  2287. <dd><p>A definition, which goes in the initialized data section of the output

  2288. file.

  2289. </p>

  2290. </dd>

  2291. <dt>&lsquo;<samp>extern int i;</samp>&rsquo;</dt>

  2292. <dd><p>An undefined reference, which does not allocate space.

  2293. There must be either a definition or a common symbol for the

  2294. variable somewhere.

  2295. </p>

  2296. </dd>

  2297. <dt>&lsquo;<samp>int i;</samp>&rsquo;</dt>

  2298. <dd><p>A common symbol.  If there are only (one or more) common symbols for a

  2299. variable, it goes in the uninitialized data area of the output file.

  2300. The linker merges multiple common symbols for the same variable into a

  2301. single symbol.  If they are of different sizes, it picks the largest

  2302. size.  The linker turns a common symbol into a declaration, if there is

  2303. a definition of the same variable.

  2304. </p></dd>

  2305. </dl>

  2306. 

  2307. <p>The &lsquo;<samp>--warn-common</samp>&rsquo; option can produce five kinds of warnings.

  2308. Each warning consists of a pair of lines: the first describes the symbol

  2309. just encountered, and the second describes the previous symbol

  2310. encountered with the same name.  One or both of the two symbols will be

  2311. a common symbol.

  2312. </p>

  2313. <ol>

  2314. <li> Turning a common symbol into a reference, because there is already a

  2315. definition for the symbol.

  2316. <div class="smallexample">

  2317. <pre class="smallexample"><var>file</var>(<var>section</var>): warning: common of `<var>symbol</var>'

  2318.    overridden by definition

  2319. <var>file</var>(<var>section</var>): warning: defined here

  2320. </pre></div>

  2321. 

  2322. </li><li> Turning a common symbol into a reference, because a later definition for

  2323. the symbol is encountered.  This is the same as the previous case,

  2324. except that the symbols are encountered in a different order.

  2325. <div class="smallexample">

  2326. <pre class="smallexample"><var>file</var>(<var>section</var>): warning: definition of `<var>symbol</var>'

  2327.    overriding common

  2328. <var>file</var>(<var>section</var>): warning: common is here

  2329. </pre></div>

  2330. 

  2331. </li><li> Merging a common symbol with a previous same-sized common symbol.

  2332. <div class="smallexample">

  2333. <pre class="smallexample"><var>file</var>(<var>section</var>): warning: multiple common

  2334.    of `<var>symbol</var>'

  2335. <var>file</var>(<var>section</var>): warning: previous common is here

  2336. </pre></div>

  2337. 

  2338. </li><li> Merging a common symbol with a previous larger common symbol.

  2339. <div class="smallexample">

  2340. <pre class="smallexample"><var>file</var>(<var>section</var>): warning: common of `<var>symbol</var>'

  2341.    overridden by larger common

  2342. <var>file</var>(<var>section</var>): warning: larger common is here

  2343. </pre></div>

  2344. 

  2345. </li><li> Merging a common symbol with a previous smaller common symbol.  This is

  2346. the same as the previous case, except that the symbols are

  2347. encountered in a different order.

  2348. <div class="smallexample">

  2349. <pre class="smallexample"><var>file</var>(<var>section</var>): warning: common of `<var>symbol</var>'

  2350.    overriding smaller common

  2351. <var>file</var>(<var>section</var>): warning: smaller common is here

  2352. </pre></div>

  2353. </li></ol>

  2354. 

  2355. <a name="index-_002d_002dwarn_002dconstructors"></a>

  2356. </dd>

  2357. <dt><code>--warn-constructors</code></dt>

  2358. <dd><p>Warn if any global constructors are used.  This is only useful for a few

  2359. object file formats.  For formats like COFF or ELF, the linker can not

  2360. detect the use of global constructors.

  2361. </p>

  2362. <a name="index-_002d_002dwarn_002dmultiple_002dgp"></a>

  2363. </dd>

  2364. <dt><code>--warn-multiple-gp</code></dt>

  2365. <dd><p>Warn if multiple global pointer values are required in the output file.

  2366. This is only meaningful for certain processors, such as the Alpha.

  2367. Specifically, some processors put large-valued constants in a special

  2368. section.  A special register (the global pointer) points into the middle

  2369. of this section, so that constants can be loaded efficiently via a

  2370. base-register relative addressing mode.  Since the offset in

  2371. base-register relative mode is fixed and relatively small (e.g., 16

  2372. bits), this limits the maximum size of the constant pool.  Thus, in

  2373. large programs, it is often necessary to use multiple global pointer

  2374. values in order to be able to address all possible constants.  This

  2375. option causes a warning to be issued whenever this case occurs.

  2376. </p>

  2377. <a name="index-_002d_002dwarn_002donce"></a>

  2378. <a name="index-warnings_002c-on-undefined-symbols"></a>

  2379. <a name="index-undefined-symbols_002c-warnings-on"></a>

  2380. </dd>

  2381. <dt><code>--warn-once</code></dt>

  2382. <dd><p>Only warn once for each undefined symbol, rather than once per module

  2383. which refers to it.

  2384. </p>

  2385. <a name="index-_002d_002dwarn_002dsection_002dalign"></a>

  2386. <a name="index-warnings_002c-on-section-alignment"></a>

  2387. <a name="index-section-alignment_002c-warnings-on"></a>

  2388. </dd>

  2389. <dt><code>--warn-section-align</code></dt>

  2390. <dd><p>Warn if the address of an output section is changed because of

  2391. alignment.  Typically, the alignment will be set by an input section.

  2392. The address will only be changed if it not explicitly specified; that

  2393. is, if the <code>SECTIONS</code> command does not specify a start address for

  2394. the section (see <a href="SECTIONS.html#SECTIONS">SECTIONS</a>).

  2395. </p>

  2396. <a name="index-_002d_002dwarn_002dtextrel"></a>

  2397. </dd>

  2398. <dt><code>--warn-textrel</code></dt>

  2399. <dd><p>Warn if the linker adds DT_TEXTREL to a position-independent executable

  2400. or shared object.

  2401. </p>

  2402. <a name="index-_002d_002dwarn_002dalternate_002dem"></a>

  2403. </dd>

  2404. <dt><code>--warn-alternate-em</code></dt>

  2405. <dd><p>Warn if an object has alternate ELF machine code.

  2406. </p>

  2407. <a name="index-_002d_002dwarn_002dunresolved_002dsymbols"></a>

  2408. </dd>

  2409. <dt><code>--warn-unresolved-symbols</code></dt>

  2410. <dd><p>If the linker is going to report an unresolved symbol (see the option

  2411. <samp>--unresolved-symbols</samp>) it will normally generate an error.

  2412. This option makes it generate a warning instead.

  2413. </p>

  2414. <a name="index-_002d_002derror_002dunresolved_002dsymbols"></a>

  2415. </dd>

  2416. <dt><code>--error-unresolved-symbols</code></dt>

  2417. <dd><p>This restores the linker&rsquo;s default behaviour of generating errors when

  2418. it is reporting unresolved symbols.

  2419. </p>

  2420. <a name="index-_002d_002dwhole_002darchive"></a>

  2421. <a name="index-including-an-entire-archive"></a>

  2422. </dd>

  2423. <dt><code>--whole-archive</code></dt>

  2424. <dd><p>For each archive mentioned on the command line after the

  2425. <samp>--whole-archive</samp> option, include every object file in the archive

  2426. in the link, rather than searching the archive for the required object

  2427. files.  This is normally used to turn an archive file into a shared

  2428. library, forcing every object to be included in the resulting shared

  2429. library.  This option may be used more than once.

  2430. </p>

  2431. <p>Two notes when using this option from gcc: First, gcc doesn&rsquo;t know

  2432. about this option, so you have to use <samp>-Wl,-whole-archive</samp>.

  2433. Second, don&rsquo;t forget to use <samp>-Wl,-no-whole-archive</samp> after your

  2434. list of archives, because gcc will add its own list of archives to

  2435. your link and you may not want this flag to affect those as well.

  2436. </p>

  2437. <a name="index-_002d_002dwrap_003dsymbol"></a>

  2438. </dd>

  2439. <dt><code>--wrap=<var>symbol</var></code></dt>

  2440. <dd><p>Use a wrapper function for <var>symbol</var>.  Any undefined reference to

  2441. <var>symbol</var> will be resolved to <code>__wrap_<var>symbol</var></code>.  Any

  2442. undefined reference to <code>__real_<var>symbol</var></code> will be resolved to

  2443. <var>symbol</var>.

  2444. </p>

  2445. <p>This can be used to provide a wrapper for a system function.  The

  2446. wrapper function should be called <code>__wrap_<var>symbol</var></code>.  If it

  2447. wishes to call the system function, it should call

  2448. <code>__real_<var>symbol</var></code>.

  2449. </p>

  2450. <p>Here is a trivial example:

  2451. </p>

  2452. <div class="smallexample">

  2453. <pre class="smallexample">void *

  2454. __wrap_malloc (size_t c)

  2455. {

  2456.   printf (&quot;malloc called with %zu\n&quot;, c);

  2457.   return __real_malloc (c);

  2458. }

  2459. </pre></div>

  2460. 

  2461. <p>If you link other code with this file using <samp>--wrap malloc</samp>, then

  2462. all calls to <code>malloc</code> will call the function <code>__wrap_malloc</code>

  2463. instead.  The call to <code>__real_malloc</code> in <code>__wrap_malloc</code> will

  2464. call the real <code>malloc</code> function.

  2465. </p>

  2466. <p>You may wish to provide a <code>__real_malloc</code> function as well, so that

  2467. links without the <samp>--wrap</samp> option will succeed.  If you do this,

  2468. you should not put the definition of <code>__real_malloc</code> in the same

  2469. file as <code>__wrap_malloc</code>; if you do, the assembler may resolve the

  2470. call before the linker has a chance to wrap it to <code>malloc</code>.

  2471. </p>

  2472. <p>Only undefined references are replaced by the linker.  So, translation unit

  2473. internal references to <var>symbol</var> are not resolved to

  2474. <code>__wrap_<var>symbol</var></code>.  In the next example, the call to <code>f</code> in

  2475. <code>g</code> is not resolved to <code>__wrap_f</code>.

  2476. </p>

  2477. <div class="smallexample">

  2478. <pre class="smallexample">int

  2479. f (void)

  2480. {

  2481.   return 123;

  2482. }

  2483. 

  2484. int

  2485. g (void)

  2486. {

  2487.   return f();

  2488. }

  2489. </pre></div>

  2490. 

  2491. <a name="index-_002d_002deh_002dframe_002dhdr"></a>

  2492. <a name="index-_002d_002dno_002deh_002dframe_002dhdr"></a>

  2493. </dd>

  2494. <dt><code>--eh-frame-hdr</code></dt>

  2495. <dt><code>--no-eh-frame-hdr</code></dt>

  2496. <dd><p>Request (<samp>--eh-frame-hdr</samp>) or suppress

  2497. (<samp>--no-eh-frame-hdr</samp>) the creation of <code>.eh_frame_hdr</code>

  2498. section and ELF <code>PT_GNU_EH_FRAME</code> segment header.

  2499. </p>

  2500. <a name="index-_002d_002dld_002dgenerated_002dunwind_002dinfo"></a>

  2501. </dd>

  2502. <dt><code>--no-ld-generated-unwind-info</code></dt>

  2503. <dd><p>Request creation of <code>.eh_frame</code> unwind info for linker

  2504. generated code sections like PLT.  This option is on by default

  2505. if linker generated unwind info is supported.

  2506. </p>

  2507. <a name="index-_002d_002denable_002dnew_002ddtags"></a>

  2508. <a name="index-_002d_002ddisable_002dnew_002ddtags"></a>

  2509. </dd>

  2510. <dt><code>--enable-new-dtags</code></dt>

  2511. <dt><code>--disable-new-dtags</code></dt>

  2512. <dd><p>This linker can create the new dynamic tags in ELF. But the older ELF

  2513. systems may not understand them. If you specify

  2514. <samp>--enable-new-dtags</samp>, the new dynamic tags will be created as needed

  2515. and older dynamic tags will be omitted.

  2516. If you specify <samp>--disable-new-dtags</samp>, no new dynamic tags will be

  2517. created. By default, the new dynamic tags are not created. Note that

  2518. those options are only available for ELF systems.

  2519. </p>

  2520. <a name="index-_002d_002dhash_002dsize_003dnumber"></a>

  2521. </dd>

  2522. <dt><code>--hash-size=<var>number</var></code></dt>

  2523. <dd><p>Set the default size of the linker&rsquo;s hash tables to a prime number

  2524. close to <var>number</var>.  Increasing this value can reduce the length of

  2525. time it takes the linker to perform its tasks, at the expense of

  2526. increasing the linker&rsquo;s memory requirements.  Similarly reducing this

  2527. value can reduce the memory requirements at the expense of speed.

  2528. </p>

  2529. <a name="index-_002d_002dhash_002dstyle_003dstyle"></a>

  2530. </dd>

  2531. <dt><code>--hash-style=<var>style</var></code></dt>

  2532. <dd><p>Set the type of linker&rsquo;s hash table(s).  <var>style</var> can be either

  2533. <code>sysv</code> for classic ELF <code>.hash</code> section, <code>gnu</code> for

  2534. new style GNU <code>.gnu.hash</code> section or <code>both</code> for both

  2535. the classic ELF <code>.hash</code> and new style GNU <code>.gnu.hash</code>

  2536. hash tables.  The default depends upon how the linker was configured,

  2537. but for most Linux based systems it will be <code>both</code>.

  2538. </p>

  2539. <a name="index-_002d_002dcompress_002ddebug_002dsections_003dnone"></a>

  2540. <a name="index-_002d_002dcompress_002ddebug_002dsections_003dzlib"></a>

  2541. <a name="index-_002d_002dcompress_002ddebug_002dsections_003dzlib_002dgnu"></a>

  2542. <a name="index-_002d_002dcompress_002ddebug_002dsections_003dzlib_002dgabi"></a>

  2543. </dd>

  2544. <dt><code>--compress-debug-sections=none</code></dt>

  2545. <dt><code>--compress-debug-sections=zlib</code></dt>

  2546. <dt><code>--compress-debug-sections=zlib-gnu</code></dt>

  2547. <dt><code>--compress-debug-sections=zlib-gabi</code></dt>

  2548. <dd><p>On ELF platforms, these options control how DWARF debug sections are

  2549. compressed using zlib.

  2550. </p>

  2551. <p><samp>--compress-debug-sections=none</samp> doesn&rsquo;t compress DWARF debug

  2552. sections.  <samp>--compress-debug-sections=zlib-gnu</samp> compresses

  2553. DWARF debug sections and renames them to begin with &lsquo;<samp>.zdebug</samp>&rsquo;

  2554. instead of &lsquo;<samp>.debug</samp>&rsquo;.  <samp>--compress-debug-sections=zlib-gabi</samp>

  2555. also compresses DWARF debug sections, but rather than renaming them it

  2556. sets the SHF_COMPRESSED flag in the sections&rsquo; headers.

  2557. </p>

  2558. <p>The <samp>--compress-debug-sections=zlib</samp> option is an alias for

  2559. <samp>--compress-debug-sections=zlib-gabi</samp>.

  2560. </p>

  2561. <p>Note that this option overrides any compression in input debug

  2562. sections, so if a binary is linked with <samp>--compress-debug-sections=none</samp>

  2563. for example, then any compressed debug sections in input files will be

  2564. uncompressed before they are copied into the output binary.

  2565. </p>

  2566. <p>The default compression behaviour varies depending upon the target

  2567. involved and the configure options used to build the toolchain.  The

  2568. default can be determined by examining the output from the linker&rsquo;s

  2569. <samp>--help</samp> option.

  2570. </p>

  2571. <a name="index-_002d_002dreduce_002dmemory_002doverheads"></a>

  2572. </dd>

  2573. <dt><code>--reduce-memory-overheads</code></dt>

  2574. <dd><p>This option reduces memory requirements at ld runtime, at the expense of

  2575. linking speed.  This was introduced to select the old O(n^2) algorithm

  2576. for link map file generation, rather than the new O(n) algorithm which uses

  2577. about 40% more memory for symbol storage.

  2578. </p>

  2579. <p>Another effect of the switch is to set the default hash table size to

  2580. 1021, which again saves memory at the cost of lengthening the linker&rsquo;s

  2581. run time.  This is not done however if the <samp>--hash-size</samp> switch

  2582. has been used.

  2583. </p>

  2584. <p>The <samp>--reduce-memory-overheads</samp> switch may be also be used to

  2585. enable other tradeoffs in future versions of the linker.

  2586. </p>

  2587. <a name="index-_002d_002dbuild_002did"></a>

  2588. <a name="index-_002d_002dbuild_002did_003dstyle"></a>

  2589. </dd>

  2590. <dt><code>--build-id</code></dt>

  2591. <dt><code>--build-id=<var>style</var></code></dt>

  2592. <dd><p>Request the creation of a <code>.note.gnu.build-id</code> ELF note section

  2593. or a <code>.buildid</code> COFF section.  The contents of the note are

  2594. unique bits identifying this linked file.  <var>style</var> can be

  2595. <code>uuid</code> to use 128 random bits, <code>sha1</code> to use a 160-bit

  2596. <small>SHA1</small> hash on the normative parts of the output contents,

  2597. <code>md5</code> to use a 128-bit <small>MD5</small> hash on the normative parts of

  2598. the output contents, or <code>0x<var>hexstring</var></code> to use a chosen bit

  2599. string specified as an even number of hexadecimal digits (<code>-</code> and

  2600. <code>:</code> characters between digit pairs are ignored).  If <var>style</var>

  2601. is omitted, <code>sha1</code> is used.

  2602. </p>

  2603. <p>The <code>md5</code> and <code>sha1</code> styles produces an identifier

  2604. that is always the same in an identical output file, but will be

  2605. unique among all nonidentical output files.  It is not intended

  2606. to be compared as a checksum for the file&rsquo;s contents.  A linked

  2607. file may be changed later by other tools, but the build ID bit

  2608. string identifying the original linked file does not change.

  2609. </p>

  2610. <p>Passing <code>none</code> for <var>style</var> disables the setting from any

  2611. <code>--build-id</code> options earlier on the command line.

  2612. </p></dd>

  2613. </dl>

  2614. 

  2615. 

  2616. <a name="Options-Specific-to-i386-PE-Targets"></a>

  2617. <h4 class="subsection">2.1.1 Options Specific to i386 PE Targets</h4>

  2618. 

  2619. 

  2620. <p>The i386 PE linker supports the <samp>-shared</samp> option, which causes

  2621. the output to be a dynamically linked library (DLL) instead of a

  2622. normal executable.  You should name the output <code>*.dll</code> when you

  2623. use this option.  In addition, the linker fully supports the standard

  2624. <code>*.def</code> files, which may be specified on the linker command line

  2625. like an object file (in fact, it should precede archives it exports

  2626. symbols from, to ensure that they get linked in, just like a normal

  2627. object file).

  2628. </p>

  2629. <p>In addition to the options common to all targets, the i386 PE linker

  2630. support additional command-line options that are specific to the i386

  2631. PE target.  Options that take values may be separated from their

  2632. values by either a space or an equals sign.

  2633. </p>

  2634. <dl compact="compact">

  2635. <dd>

  2636. <a name="index-_002d_002dadd_002dstdcall_002dalias"></a>

  2637. </dd>

  2638. <dt><code>--add-stdcall-alias</code></dt>

  2639. <dd><p>If given, symbols with a stdcall suffix (@<var>nn</var>) will be exported

  2640. as-is and also with the suffix stripped.

  2641. [This option is specific to the i386 PE targeted port of the linker]

  2642. </p>

  2643. <a name="index-_002d_002dbase_002dfile"></a>

  2644. </dd>

  2645. <dt><code>--base-file <var>file</var></code></dt>

  2646. <dd><p>Use <var>file</var> as the name of a file in which to save the base

  2647. addresses of all the relocations needed for generating DLLs with

  2648. <samp>dlltool</samp>.

  2649. [This is an i386 PE specific option]

  2650. </p>

  2651. <a name="index-_002d_002ddll"></a>

  2652. </dd>

  2653. <dt><code>--dll</code></dt>

  2654. <dd><p>Create a DLL instead of a regular executable.  You may also use

  2655. <samp>-shared</samp> or specify a <code>LIBRARY</code> in a given <code>.def</code>

  2656. file.

  2657. [This option is specific to the i386 PE targeted port of the linker]

  2658. </p>

  2659. <a name="index-_002d_002denable_002dlong_002dsection_002dnames"></a>

  2660. <a name="index-_002d_002ddisable_002dlong_002dsection_002dnames"></a>

  2661. </dd>

  2662. <dt><code>--enable-long-section-names</code></dt>

  2663. <dt><code>--disable-long-section-names</code></dt>

  2664. <dd><p>The PE variants of the COFF object format add an extension that permits

  2665. the use of section names longer than eight characters, the normal limit

  2666. for COFF.  By default, these names are only allowed in object files, as

  2667. fully-linked executable images do not carry the COFF string table required

  2668. to support the longer names.  As a GNU extension, it is possible to

  2669. allow their use in executable images as well, or to (probably pointlessly!)

  2670. disallow it in object files, by using these two options.  Executable images

  2671. generated with these long section names are slightly non-standard, carrying

  2672. as they do a string table, and may generate confusing output when examined

  2673. with non-GNU PE-aware tools, such as file viewers and dumpers.  However,

  2674. GDB relies on the use of PE long section names to find Dwarf-2 debug

  2675. information sections in an executable image at runtime, and so if neither

  2676. option is specified on the command-line, <code>ld</code> will enable long

  2677. section names, overriding the default and technically correct behaviour,

  2678. when it finds the presence of debug information while linking an executable

  2679. image and not stripping symbols.

  2680. [This option is valid for all PE targeted ports of the linker]

  2681. </p>

  2682. <a name="index-_002d_002denable_002dstdcall_002dfixup"></a>

  2683. <a name="index-_002d_002ddisable_002dstdcall_002dfixup"></a>

  2684. </dd>

  2685. <dt><code>--enable-stdcall-fixup</code></dt>

  2686. <dt><code>--disable-stdcall-fixup</code></dt>

  2687. <dd><p>If the link finds a symbol that it cannot resolve, it will attempt to

  2688. do &ldquo;fuzzy linking&rdquo; by looking for another defined symbol that differs

  2689. only in the format of the symbol name (cdecl vs stdcall) and will

  2690. resolve that symbol by linking to the match.  For example, the

  2691. undefined symbol <code>_foo</code> might be linked to the function

  2692. <code>_foo@12</code>, or the undefined symbol <code>_bar@16</code> might be linked

  2693. to the function <code>_bar</code>.  When the linker does this, it prints a

  2694. warning, since it normally should have failed to link, but sometimes

  2695. import libraries generated from third-party dlls may need this feature

  2696. to be usable.  If you specify <samp>--enable-stdcall-fixup</samp>, this

  2697. feature is fully enabled and warnings are not printed.  If you specify

  2698. <samp>--disable-stdcall-fixup</samp>, this feature is disabled and such

  2699. mismatches are considered to be errors.

  2700. [This option is specific to the i386 PE targeted port of the linker]

  2701. </p>

  2702. <a name="index-_002d_002dleading_002dunderscore"></a>

  2703. <a name="index-_002d_002dno_002dleading_002dunderscore"></a>

  2704. </dd>

  2705. <dt><code>--leading-underscore</code></dt>

  2706. <dt><code>--no-leading-underscore</code></dt>

  2707. <dd><p>For most targets default symbol-prefix is an underscore and is defined

  2708. in target&rsquo;s description. By this option it is possible to

  2709. disable/enable the default underscore symbol-prefix.

  2710. </p>

  2711. <a name="index-DLLs_002c-creating"></a>

  2712. <a name="index-_002d_002dexport_002dall_002dsymbols"></a>

  2713. </dd>

  2714. <dt><code>--export-all-symbols</code></dt>

  2715. <dd><p>If given, all global symbols in the objects used to build a DLL will

  2716. be exported by the DLL.  Note that this is the default if there

  2717. otherwise wouldn&rsquo;t be any exported symbols.  When symbols are

  2718. explicitly exported via DEF files or implicitly exported via function

  2719. attributes, the default is to not export anything else unless this

  2720. option is given.  Note that the symbols <code>DllMain@12</code>,

  2721. <code>DllEntryPoint@0</code>, <code>DllMainCRTStartup@12</code>, and

  2722. <code>impure_ptr</code> will not be automatically

  2723. exported.  Also, symbols imported from other DLLs will not be

  2724. re-exported, nor will symbols specifying the DLL&rsquo;s internal layout

  2725. such as those beginning with <code>_head_</code> or ending with

  2726. <code>_iname</code>.  In addition, no symbols from <code>libgcc</code>,

  2727. <code>libstd++</code>, <code>libmingw32</code>, or <code>crtX.o</code> will be exported.

  2728. Symbols whose names begin with <code>__rtti_</code> or <code>__builtin_</code> will

  2729. not be exported, to help with C++ DLLs.  Finally, there is an

  2730. extensive list of cygwin-private symbols that are not exported

  2731. (obviously, this applies on when building DLLs for cygwin targets).

  2732. These cygwin-excludes are: <code>_cygwin_dll_entry@12</code>,

  2733. <code>_cygwin_crt0_common@8</code>, <code>_cygwin_noncygwin_dll_entry@12</code>,

  2734. <code>_fmode</code>, <code>_impure_ptr</code>, <code>cygwin_attach_dll</code>,

  2735. <code>cygwin_premain0</code>, <code>cygwin_premain1</code>, <code>cygwin_premain2</code>,

  2736. <code>cygwin_premain3</code>, and <code>environ</code>.

  2737. [This option is specific to the i386 PE targeted port of the linker]

  2738. </p>

  2739. <a name="index-_002d_002dexclude_002dsymbols"></a>

  2740. </dd>

  2741. <dt><code>--exclude-symbols <var>symbol</var>,<var>symbol</var>,...</code></dt>

  2742. <dd><p>Specifies a list of symbols which should not be automatically

  2743. exported.  The symbol names may be delimited by commas or colons.

  2744. [This option is specific to the i386 PE targeted port of the linker]

  2745. </p>

  2746. <a name="index-_002d_002dexclude_002dall_002dsymbols"></a>

  2747. </dd>

  2748. <dt><code>--exclude-all-symbols</code></dt>

  2749. <dd><p>Specifies no symbols should be automatically exported.

  2750. [This option is specific to the i386 PE targeted port of the linker]

  2751. </p>

  2752. <a name="index-_002d_002dfile_002dalignment"></a>

  2753. </dd>

  2754. <dt><code>--file-alignment</code></dt>

  2755. <dd><p>Specify the file alignment.  Sections in the file will always begin at

  2756. file offsets which are multiples of this number.  This defaults to

  2757. 512.

  2758. [This option is specific to the i386 PE targeted port of the linker]

  2759. </p>

  2760. <a name="index-heap-size"></a>

  2761. <a name="index-_002d_002dheap"></a>

  2762. </dd>

  2763. <dt><code>--heap <var>reserve</var></code></dt>

  2764. <dt><code>--heap <var>reserve</var>,<var>commit</var></code></dt>

  2765. <dd><p>Specify the number of bytes of memory to reserve (and optionally commit)

  2766. to be used as heap for this program.  The default is 1MB reserved, 4K

  2767. committed.

  2768. [This option is specific to the i386 PE targeted port of the linker]

  2769. </p>

  2770. <a name="index-image-base"></a>

  2771. <a name="index-_002d_002dimage_002dbase"></a>

  2772. </dd>

  2773. <dt><code>--image-base <var>value</var></code></dt>

  2774. <dd><p>Use <var>value</var> as the base address of your program or dll.  This is

  2775. the lowest memory location that will be used when your program or dll

  2776. is loaded.  To reduce the need to relocate and improve performance of

  2777. your dlls, each should have a unique base address and not overlap any

  2778. other dlls.  The default is 0x400000 for executables, and 0x10000000

  2779. for dlls.

  2780. [This option is specific to the i386 PE targeted port of the linker]

  2781. </p>

  2782. <a name="index-_002d_002dkill_002dat"></a>

  2783. </dd>

  2784. <dt><code>--kill-at</code></dt>

  2785. <dd><p>If given, the stdcall suffixes (@<var>nn</var>) will be stripped from

  2786. symbols before they are exported.

  2787. [This option is specific to the i386 PE targeted port of the linker]

  2788. </p>

  2789. <a name="index-_002d_002dlarge_002daddress_002daware"></a>

  2790. </dd>

  2791. <dt><code>--large-address-aware</code></dt>

  2792. <dd><p>If given, the appropriate bit in the &ldquo;Characteristics&rdquo; field of the COFF

  2793. header is set to indicate that this executable supports virtual addresses

  2794. greater than 2 gigabytes.  This should be used in conjunction with the /3GB

  2795. or /USERVA=<var>value</var> megabytes switch in the &ldquo;[operating systems]&rdquo;

  2796. section of the BOOT.INI.  Otherwise, this bit has no effect.

  2797. [This option is specific to PE targeted ports of the linker]

  2798. </p>

  2799. <a name="index-_002d_002ddisable_002dlarge_002daddress_002daware"></a>

  2800. </dd>

  2801. <dt><code>--disable-large-address-aware</code></dt>

  2802. <dd><p>Reverts the effect of a previous &lsquo;<samp>--large-address-aware</samp>&rsquo; option.

  2803. This is useful if &lsquo;<samp>--large-address-aware</samp>&rsquo; is always set by the compiler

  2804. driver (e.g. Cygwin gcc) and the executable does not support virtual

  2805. addresses greater than 2 gigabytes.

  2806. [This option is specific to PE targeted ports of the linker]

  2807. </p>

  2808. <a name="index-_002d_002dmajor_002dimage_002dversion"></a>

  2809. </dd>

  2810. <dt><code>--major-image-version <var>value</var></code></dt>

  2811. <dd><p>Sets the major number of the &ldquo;image version&rdquo;.  Defaults to 1.

  2812. [This option is specific to the i386 PE targeted port of the linker]

  2813. </p>

  2814. <a name="index-_002d_002dmajor_002dos_002dversion"></a>

  2815. </dd>

  2816. <dt><code>--major-os-version <var>value</var></code></dt>

  2817. <dd><p>Sets the major number of the &ldquo;os version&rdquo;.  Defaults to 4.

  2818. [This option is specific to the i386 PE targeted port of the linker]

  2819. </p>

  2820. <a name="index-_002d_002dmajor_002dsubsystem_002dversion"></a>

  2821. </dd>

  2822. <dt><code>--major-subsystem-version <var>value</var></code></dt>

  2823. <dd><p>Sets the major number of the &ldquo;subsystem version&rdquo;.  Defaults to 4.

  2824. [This option is specific to the i386 PE targeted port of the linker]

  2825. </p>

  2826. <a name="index-_002d_002dminor_002dimage_002dversion"></a>

  2827. </dd>

  2828. <dt><code>--minor-image-version <var>value</var></code></dt>

  2829. <dd><p>Sets the minor number of the &ldquo;image version&rdquo;.  Defaults to 0.

  2830. [This option is specific to the i386 PE targeted port of the linker]

  2831. </p>

  2832. <a name="index-_002d_002dminor_002dos_002dversion"></a>

  2833. </dd>

  2834. <dt><code>--minor-os-version <var>value</var></code></dt>

  2835. <dd><p>Sets the minor number of the &ldquo;os version&rdquo;.  Defaults to 0.

  2836. [This option is specific to the i386 PE targeted port of the linker]

  2837. </p>

  2838. <a name="index-_002d_002dminor_002dsubsystem_002dversion"></a>

  2839. </dd>

  2840. <dt><code>--minor-subsystem-version <var>value</var></code></dt>

  2841. <dd><p>Sets the minor number of the &ldquo;subsystem version&rdquo;.  Defaults to 0.

  2842. [This option is specific to the i386 PE targeted port of the linker]

  2843. </p>

  2844. <a name="index-DEF-files_002c-creating"></a>

  2845. <a name="index-DLLs_002c-creating-1"></a>

  2846. <a name="index-_002d_002doutput_002ddef"></a>

  2847. </dd>

  2848. <dt><code>--output-def <var>file</var></code></dt>

  2849. <dd><p>The linker will create the file <var>file</var> which will contain a DEF

  2850. file corresponding to the DLL the linker is generating.  This DEF file

  2851. (which should be called <code>*.def</code>) may be used to create an import

  2852. library with <code>dlltool</code> or may be used as a reference to

  2853. automatically or implicitly exported symbols.

  2854. [This option is specific to the i386 PE targeted port of the linker]

  2855. </p>

  2856. <a name="index-DLLs_002c-creating-2"></a>

  2857. <a name="index-_002d_002denable_002dauto_002dimage_002dbase"></a>

  2858. </dd>

  2859. <dt><code>--enable-auto-image-base</code></dt>

  2860. <dt><code>--enable-auto-image-base=<var>value</var></code></dt>

  2861. <dd><p>Automatically choose the image base for DLLs, optionally starting with base

  2862. <var>value</var>, unless one is specified using the <code>--image-base</code> argument.

  2863. By using a hash generated from the dllname to create unique image bases

  2864. for each DLL, in-memory collisions and relocations which can delay program

  2865. execution are avoided.

  2866. [This option is specific to the i386 PE targeted port of the linker]

  2867. </p>

  2868. <a name="index-_002d_002ddisable_002dauto_002dimage_002dbase"></a>

  2869. </dd>

  2870. <dt><code>--disable-auto-image-base</code></dt>

  2871. <dd><p>Do not automatically generate a unique image base.  If there is no

  2872. user-specified image base (<code>--image-base</code>) then use the platform

  2873. default.

  2874. [This option is specific to the i386 PE targeted port of the linker]

  2875. </p>

  2876. <a name="index-DLLs_002c-linking-to"></a>

  2877. <a name="index-_002d_002ddll_002dsearch_002dprefix"></a>

  2878. </dd>

  2879. <dt><code>--dll-search-prefix <var>string</var></code></dt>

  2880. <dd><p>When linking dynamically to a dll without an import library,

  2881. search for <code>&lt;string&gt;&lt;basename&gt;.dll</code> in preference to

  2882. <code>lib&lt;basename&gt;.dll</code>. This behaviour allows easy distinction

  2883. between DLLs built for the various &quot;subplatforms&quot;: native, cygwin,

  2884. uwin, pw, etc.  For instance, cygwin DLLs typically use

  2885. <code>--dll-search-prefix=cyg</code>.

  2886. [This option is specific to the i386 PE targeted port of the linker]

  2887. </p>

  2888. <a name="index-_002d_002denable_002dauto_002dimport"></a>

  2889. </dd>

  2890. <dt><code>--enable-auto-import</code></dt>

  2891. <dd><p>Do sophisticated linking of <code>_symbol</code> to <code>__imp__symbol</code> for

  2892. DATA imports from DLLs, thus making it possible to bypass the dllimport

  2893. mechanism on the user side and to reference unmangled symbol names.

  2894. [This option is specific to the i386 PE targeted port of the linker]

  2895. </p>

  2896. <p>The following remarks pertain to the original implementation of the

  2897. feature and are obsolete nowadays for Cygwin and MinGW targets.

  2898. </p>

  2899. <p>Note: Use of the &rsquo;auto-import&rsquo; extension will cause the text section

  2900. of the image file to be made writable. This does not conform to the

  2901. PE-COFF format specification published by Microsoft.

  2902. </p>

  2903. <p>Note - use of the &rsquo;auto-import&rsquo; extension will also cause read only

  2904. data which would normally be placed into the .rdata section to be

  2905. placed into the .data section instead.  This is in order to work

  2906. around a problem with consts that is described here:

  2907. http://www.cygwin.com/ml/cygwin/2004-09/msg01101.html

  2908. </p>

  2909. <p>Using &rsquo;auto-import&rsquo; generally will &rsquo;just work&rsquo; &ndash; but sometimes you may

  2910. see this message:

  2911. </p>

  2912. <p>&quot;variable &rsquo;&lt;var&gt;&rsquo; can&rsquo;t be auto-imported. Please read the

  2913. documentation for ld&rsquo;s <code>--enable-auto-import</code> for details.&quot;

  2914. </p>

  2915. <p>This message occurs when some (sub)expression accesses an address

  2916. ultimately given by the sum of two constants (Win32 import tables only

  2917. allow one).  Instances where this may occur include accesses to member

  2918. fields of struct variables imported from a DLL, as well as using a

  2919. constant index into an array variable imported from a DLL.  Any

  2920. multiword variable (arrays, structs, long long, etc) may trigger

  2921. this error condition.  However, regardless of the exact data type

  2922. of the offending exported variable, ld will always detect it, issue

  2923. the warning, and exit.

  2924. </p>

  2925. <p>There are several ways to address this difficulty, regardless of the

  2926. data type of the exported variable:

  2927. </p>

  2928. <p>One way is to use &ndash;enable-runtime-pseudo-reloc switch. This leaves the task

  2929. of adjusting references in your client code for runtime environment, so

  2930. this method works only when runtime environment supports this feature.

  2931. </p>

  2932. <p>A second solution is to force one of the &rsquo;constants&rsquo; to be a variable &ndash;

  2933. that is, unknown and un-optimizable at compile time.  For arrays,

  2934. there are two possibilities: a) make the indexee (the array&rsquo;s address)

  2935. a variable, or b) make the &rsquo;constant&rsquo; index a variable.  Thus:

  2936. </p>

  2937. <div class="example">

  2938. <pre class="example">extern type extern_array[];

  2939. extern_array[1] --&gt;

  2940.    { volatile type *t=extern_array; t[1] }

  2941. </pre></div>

  2942. 

  2943. <p>or

  2944. </p>

  2945. <div class="example">

  2946. <pre class="example">extern type extern_array[];

  2947. extern_array[1] --&gt;

  2948.    { volatile int t=1; extern_array[t] }

  2949. </pre></div>

  2950. 

  2951. <p>For structs (and most other multiword data types) the only option

  2952. is to make the struct itself (or the long long, or the ...) variable:

  2953. </p>

  2954. <div class="example">

  2955. <pre class="example">extern struct s extern_struct;

  2956. extern_struct.field --&gt;

  2957.    { volatile struct s *t=&amp;extern_struct; t-&gt;field }

  2958. </pre></div>

  2959. 

  2960. <p>or

  2961. </p>

  2962. <div class="example">

  2963. <pre class="example">extern long long extern_ll;

  2964. extern_ll --&gt;

  2965.   { volatile long long * local_ll=&amp;extern_ll; *local_ll }

  2966. </pre></div>

  2967. 

  2968. <p>A third method of dealing with this difficulty is to abandon

  2969. &rsquo;auto-import&rsquo; for the offending symbol and mark it with

  2970. <code>__declspec(dllimport)</code>.  However, in practice that

  2971. requires using compile-time #defines to indicate whether you are

  2972. building a DLL, building client code that will link to the DLL, or

  2973. merely building/linking to a static library.   In making the choice

  2974. between the various methods of resolving the &rsquo;direct address with

  2975. constant offset&rsquo; problem, you should consider typical real-world usage:

  2976. </p>

  2977. <p>Original:

  2978. </p><div class="example">

  2979. <pre class="example">--foo.h

  2980. extern int arr[];

  2981. --foo.c

  2982. #include &quot;foo.h&quot;

  2983. void main(int argc, char **argv){

  2984.   printf(&quot;%d\n&quot;,arr[1]);

  2985. }

  2986. </pre></div>

  2987. 

  2988. <p>Solution 1:

  2989. </p><div class="example">

  2990. <pre class="example">--foo.h

  2991. extern int arr[];

  2992. --foo.c

  2993. #include &quot;foo.h&quot;

  2994. void main(int argc, char **argv){

  2995.   /* This workaround is for win32 and cygwin; do not &quot;optimize&quot; */

  2996.   volatile int *parr = arr;

  2997.   printf(&quot;%d\n&quot;,parr[1]);

  2998. }

  2999. </pre></div>

  3000. 

  3001. <p>Solution 2:

  3002. </p><div class="example">

  3003. <pre class="example">--foo.h

  3004. /* Note: auto-export is assumed (no __declspec(dllexport)) */

  3005. #if (defined(_WIN32) || defined(__CYGWIN__)) &amp;&amp; \

  3006.   !(defined(FOO_BUILD_DLL) || defined(FOO_STATIC))

  3007. #define FOO_IMPORT __declspec(dllimport)

  3008. #else

  3009. #define FOO_IMPORT

  3010. #endif

  3011. extern FOO_IMPORT int arr[];

  3012. --foo.c

  3013. #include &quot;foo.h&quot;

  3014. void main(int argc, char **argv){

  3015.   printf(&quot;%d\n&quot;,arr[1]);

  3016. }

  3017. </pre></div>

  3018. 

  3019. <p>A fourth way to avoid this problem is to re-code your

  3020. library to use a functional interface rather than a data interface

  3021. for the offending variables (e.g. set_foo() and get_foo() accessor

  3022. functions).

  3023. </p>

  3024. <a name="index-_002d_002ddisable_002dauto_002dimport"></a>

  3025. </dd>

  3026. <dt><code>--disable-auto-import</code></dt>

  3027. <dd><p>Do not attempt to do sophisticated linking of <code>_symbol</code> to

  3028. <code>__imp__symbol</code> for DATA imports from DLLs.

  3029. [This option is specific to the i386 PE targeted port of the linker]

  3030. </p>

  3031. <a name="index-_002d_002denable_002druntime_002dpseudo_002dreloc"></a>

  3032. </dd>

  3033. <dt><code>--enable-runtime-pseudo-reloc</code></dt>

  3034. <dd><p>If your code contains expressions described in &ndash;enable-auto-import section,

  3035. that is, DATA imports from DLL with non-zero offset, this switch will create

  3036. a vector of &rsquo;runtime pseudo relocations&rsquo; which can be used by runtime

  3037. environment to adjust references to such data in your client code.

  3038. [This option is specific to the i386 PE targeted port of the linker]

  3039. </p>

  3040. <a name="index-_002d_002ddisable_002druntime_002dpseudo_002dreloc"></a>

  3041. </dd>

  3042. <dt><code>--disable-runtime-pseudo-reloc</code></dt>

  3043. <dd><p>Do not create pseudo relocations for non-zero offset DATA imports from DLLs.

  3044. [This option is specific to the i386 PE targeted port of the linker]

  3045. </p>

  3046. <a name="index-_002d_002denable_002dextra_002dpe_002ddebug"></a>

  3047. </dd>

  3048. <dt><code>--enable-extra-pe-debug</code></dt>

  3049. <dd><p>Show additional debug info related to auto-import symbol thunking.

  3050. [This option is specific to the i386 PE targeted port of the linker]

  3051. </p>

  3052. <a name="index-_002d_002dsection_002dalignment"></a>

  3053. </dd>

  3054. <dt><code>--section-alignment</code></dt>

  3055. <dd><p>Sets the section alignment.  Sections in memory will always begin at

  3056. addresses which are a multiple of this number.  Defaults to 0x1000.

  3057. [This option is specific to the i386 PE targeted port of the linker]

  3058. </p>

  3059. <a name="index-stack-size"></a>

  3060. <a name="index-_002d_002dstack"></a>

  3061. </dd>

  3062. <dt><code>--stack <var>reserve</var></code></dt>

  3063. <dt><code>--stack <var>reserve</var>,<var>commit</var></code></dt>

  3064. <dd><p>Specify the number of bytes of memory to reserve (and optionally commit)

  3065. to be used as stack for this program.  The default is 2MB reserved, 4K

  3066. committed.

  3067. [This option is specific to the i386 PE targeted port of the linker]

  3068. </p>

  3069. <a name="index-_002d_002dsubsystem"></a>

  3070. </dd>

  3071. <dt><code>--subsystem <var>which</var></code></dt>

  3072. <dt><code>--subsystem <var>which</var>:<var>major</var></code></dt>

  3073. <dt><code>--subsystem <var>which</var>:<var>major</var>.<var>minor</var></code></dt>

  3074. <dd><p>Specifies the subsystem under which your program will execute.  The

  3075. legal values for <var>which</var> are <code>native</code>, <code>windows</code>,

  3076. <code>console</code>, <code>posix</code>, and <code>xbox</code>.  You may optionally set

  3077. the subsystem version also.  Numeric values are also accepted for

  3078. <var>which</var>.

  3079. [This option is specific to the i386 PE targeted port of the linker]

  3080. </p>

  3081. <p>The following options set flags in the <code>DllCharacteristics</code> field

  3082. of the PE file header:

  3083. [These options are specific to PE targeted ports of the linker]

  3084. </p>

  3085. <a name="index-_002d_002dhigh_002dentropy_002dva"></a>

  3086. </dd>

  3087. <dt><code>--high-entropy-va</code></dt>

  3088. <dd><p>Image is compatible with 64-bit address space layout randomization

  3089. (ASLR).

  3090. This option also implies <samp>--dynamicbase</samp> and

  3091. <samp>--enable-reloc-section</samp>.

  3092. </p>

  3093. <a name="index-_002d_002ddynamicbase"></a>

  3094. </dd>

  3095. <dt><code>--dynamicbase</code></dt>

  3096. <dd><p>The image base address may be relocated using address space layout

  3097. randomization (ASLR).  This feature was introduced with MS Windows

  3098. Vista for i386 PE targets.

  3099. This option also implies <samp>--enable-reloc-section</samp>.

  3100. </p>

  3101. <a name="index-_002d_002dforceinteg"></a>

  3102. </dd>

  3103. <dt><code>--forceinteg</code></dt>

  3104. <dd><p>Code integrity checks are enforced.

  3105. </p>

  3106. <a name="index-_002d_002dnxcompat"></a>

  3107. </dd>

  3108. <dt><code>--nxcompat</code></dt>

  3109. <dd><p>The image is compatible with the Data Execution Prevention.

  3110. This feature was introduced with MS Windows XP SP2 for i386 PE targets.

  3111. </p>

  3112. <a name="index-_002d_002dno_002disolation"></a>

  3113. </dd>

  3114. <dt><code>--no-isolation</code></dt>

  3115. <dd><p>Although the image understands isolation, do not isolate the image.

  3116. </p>

  3117. <a name="index-_002d_002dno_002dseh"></a>

  3118. </dd>

  3119. <dt><code>--no-seh</code></dt>

  3120. <dd><p>The image does not use SEH. No SE handler may be called from

  3121. this image.

  3122. </p>

  3123. <a name="index-_002d_002dno_002dbind"></a>

  3124. </dd>

  3125. <dt><code>--no-bind</code></dt>

  3126. <dd><p>Do not bind this image.

  3127. </p>

  3128. <a name="index-_002d_002dwdmdriver"></a>

  3129. </dd>

  3130. <dt><code>--wdmdriver</code></dt>

  3131. <dd><p>The driver uses the MS Windows Driver Model.

  3132. </p>

  3133. <a name="index-_002d_002dtsaware"></a>

  3134. </dd>

  3135. <dt><code>--tsaware</code></dt>

  3136. <dd><p>The image is Terminal Server aware.

  3137. </p>

  3138. <a name="index-_002d_002dinsert_002dtimestamp"></a>

  3139. </dd>

  3140. <dt><code>--insert-timestamp</code></dt>

  3141. <dt><code>--no-insert-timestamp</code></dt>

  3142. <dd><p>Insert a real timestamp into the image.  This is the default behaviour

  3143. as it matches legacy code and it means that the image will work with

  3144. other, proprietary tools.  The problem with this default is that it

  3145. will result in slightly different images being produced each time the

  3146. same sources are linked.  The option <samp>--no-insert-timestamp</samp>

  3147. can be used to insert a zero value for the timestamp, this ensuring

  3148. that binaries produced from identical sources will compare

  3149. identically.

  3150. </p>

  3151. <a name="index-_002d_002denable_002dreloc_002dsection"></a>

  3152. </dd>

  3153. <dt><code>--enable-reloc-section</code></dt>

  3154. <dd><p>Create the base relocation table, which is necessary if the image

  3155. is loaded at a different image base than specified in the PE header.

  3156. </p></dd>

  3157. </dl>

  3158. 

  3159. 

  3160. <a name="Options-specific-to-C6X-uClinux-targets"></a>

  3161. <h4 class="subsection">2.1.2 Options specific to C6X uClinux targets</h4>

  3162. 

  3163. 

  3164. <p>The C6X uClinux target uses a binary format called DSBT to support shared

  3165. libraries.  Each shared library in the system needs to have a unique index;

  3166. all executables use an index of 0.

  3167. </p>

  3168. <dl compact="compact">

  3169. <dd>

  3170. <a name="index-_002d_002ddsbt_002dsize"></a>

  3171. </dd>

  3172. <dt><code>--dsbt-size <var>size</var></code></dt>

  3173. <dd><p>This option sets the number of entries in the DSBT of the current executable

  3174. or shared library to <var>size</var>.  The default is to create a table with 64

  3175. entries.

  3176. </p>

  3177. <a name="index-_002d_002ddsbt_002dindex"></a>

  3178. </dd>

  3179. <dt><code>--dsbt-index <var>index</var></code></dt>

  3180. <dd><p>This option sets the DSBT index of the current executable or shared library

  3181. to <var>index</var>.  The default is 0, which is appropriate for generating

  3182. executables.  If a shared library is generated with a DSBT index of 0, the

  3183. <code>R_C6000_DSBT_INDEX</code> relocs are copied into the output file.

  3184. </p>

  3185. <a name="index-_002d_002dno_002dmerge_002dexidx_002dentries"></a>

  3186. <p>The &lsquo;<samp>--no-merge-exidx-entries</samp>&rsquo; switch disables the merging of adjacent

  3187. exidx entries in frame unwind info.

  3188. </p>

  3189. </dd>

  3190. </dl>

  3191. 

  3192. 

  3193. <a name="Options-specific-to-C_002dSKY-targets"></a>

  3194. <h4 class="subsection">2.1.3 Options specific to C-SKY targets</h4>

  3195. 

  3196. 

  3197. <dl compact="compact">

  3198. <dd>

  3199. <a name="index-_002d_002dbranch_002dstub-on-C_002dSKY"></a>

  3200. </dd>

  3201. <dt><code>--branch-stub</code></dt>

  3202. <dd><p>This option enables linker branch relaxation by inserting branch stub

  3203. sections when needed to extend the range of branches.  This option is

  3204. usually not required since C-SKY supports branch and call instructions that

  3205. can access the full memory range and branch relaxation is normally handled by

  3206. the compiler or assembler.

  3207. </p>

  3208. <a name="index-_002d_002dstub_002dgroup_002dsize-on-C_002dSKY"></a>

  3209. </dd>

  3210. <dt><code>--stub-group-size=<var>N</var></code></dt>

  3211. <dd><p>This option allows finer control of linker branch stub creation.

  3212. It sets the maximum size of a group of input sections that can

  3213. be handled by one stub section.  A negative value of <var>N</var> locates

  3214. stub sections after their branches, while a positive value allows stub

  3215. sections to appear either before or after the branches.  Values of

  3216. &lsquo;<samp>1</samp>&rsquo; or &lsquo;<samp>-1</samp>&rsquo; indicate that the

  3217. linker should choose suitable defaults.

  3218. </p>

  3219. </dd>

  3220. </dl>

  3221. 

  3222. 

  3223. <a name="Options-specific-to-Motorola-68HC11-and-68HC12-targets"></a>

  3224. <h4 class="subsection">2.1.4 Options specific to Motorola 68HC11 and 68HC12 targets</h4>

  3225. 

  3226. 

  3227. <p>The 68HC11 and 68HC12 linkers support specific options to control the

  3228. memory bank switching mapping and trampoline code generation.

  3229. </p>

  3230. <dl compact="compact">

  3231. <dd>

  3232. <a name="index-_002d_002dno_002dtrampoline"></a>

  3233. </dd>

  3234. <dt><code>--no-trampoline</code></dt>

  3235. <dd><p>This option disables the generation of trampoline. By default a trampoline

  3236. is generated for each far function which is called using a <code>jsr</code>

  3237. instruction (this happens when a pointer to a far function is taken).

  3238. </p>

  3239. <a name="index-_002d_002dbank_002dwindow"></a>

  3240. </dd>

  3241. <dt><code>--bank-window <var>name</var></code></dt>

  3242. <dd><p>This option indicates to the linker the name of the memory region in

  3243. the &lsquo;<samp>MEMORY</samp>&rsquo; specification that describes the memory bank window.

  3244. The definition of such region is then used by the linker to compute

  3245. paging and addresses within the memory window.

  3246. </p>

  3247. </dd>

  3248. </dl>

  3249. 

  3250. 

  3251. <a name="Options-specific-to-Motorola-68K-target"></a>

  3252. <h4 class="subsection">2.1.5 Options specific to Motorola 68K target</h4>

  3253. 

  3254. 

  3255. <p>The following options are supported to control handling of GOT generation

  3256. when linking for 68K targets.

  3257. </p>

  3258. <dl compact="compact">

  3259. <dd>

  3260. <a name="index-_002d_002dgot"></a>

  3261. </dd>

  3262. <dt><code>--got=<var>type</var></code></dt>

  3263. <dd><p>This option tells the linker which GOT generation scheme to use.

  3264. <var>type</var> should be one of &lsquo;<samp>single</samp>&rsquo;, &lsquo;<samp>negative</samp>&rsquo;,

  3265. &lsquo;<samp>multigot</samp>&rsquo; or &lsquo;<samp>target</samp>&rsquo;.  For more information refer to the

  3266. Info entry for <samp>ld</samp>.

  3267. </p>

  3268. </dd>

  3269. </dl>

  3270. 

  3271. 

  3272. <a name="Options-specific-to-MIPS-targets"></a>

  3273. <h4 class="subsection">2.1.6 Options specific to MIPS targets</h4>

  3274. 

  3275. 

  3276. <p>The following options are supported to control microMIPS instruction

  3277. generation and branch relocation checks for ISA mode transitions when

  3278. linking for MIPS targets.

  3279. </p>

  3280. <dl compact="compact">

  3281. <dd>

  3282. <a name="index-_002d_002dinsn32"></a>

  3283. </dd>

  3284. <dt><code>--insn32</code></dt>

  3285. <dd><a name="index-_002d_002dno_002dinsn32"></a>

  3286. </dd>

  3287. <dt><code>--no-insn32</code></dt>

  3288. <dd><p>These options control the choice of microMIPS instructions used in code

  3289. generated by the linker, such as that in the PLT or lazy binding stubs,

  3290. or in relaxation.  If &lsquo;<samp>--insn32</samp>&rsquo; is used, then the linker only uses

  3291. 32-bit instruction encodings.  By default or if &lsquo;<samp>--no-insn32</samp>&rsquo; is

  3292. used, all instruction encodings are used, including 16-bit ones where

  3293. possible.

  3294. </p>

  3295. <a name="index-_002d_002dignore_002dbranch_002disa"></a>

  3296. </dd>

  3297. <dt><code>--ignore-branch-isa</code></dt>

  3298. <dd><a name="index-_002d_002dno_002dignore_002dbranch_002disa"></a>

  3299. </dd>

  3300. <dt><code>--no-ignore-branch-isa</code></dt>

  3301. <dd><p>These options control branch relocation checks for invalid ISA mode

  3302. transitions.  If &lsquo;<samp>--ignore-branch-isa</samp>&rsquo; is used, then the linker

  3303. accepts any branch relocations and any ISA mode transition required

  3304. is lost in relocation calculation, except for some cases of <code>BAL</code>

  3305. instructions which meet relaxation conditions and are converted to

  3306. equivalent <code>JALX</code> instructions as the associated relocation is

  3307. calculated.  By default or if &lsquo;<samp>--no-ignore-branch-isa</samp>&rsquo; is used

  3308. a check is made causing the loss of an ISA mode transition to produce

  3309. an error.

  3310. </p>

  3311. <a name="index-_002d_002dcompact_002dbranches"></a>

  3312. </dd>

  3313. <dt><code>--compact-branches</code></dt>

  3314. <dd><a name="index-_002d_002dno_002dcompact_002dbranches"></a>

  3315. </dd>

  3316. <dt><code>--no-compact-branches</code></dt>

  3317. <dd><p>These options control the generation of compact instructions by the linker

  3318. in the PLT entries for MIPS R6.

  3319. </p>

  3320. </dd>

  3321. </dl>

  3322. 

  3323. 

  3324. 

  3325. <a name="Options-specific-to-PDP11-targets"></a>

  3326. <h4 class="subsection">2.1.7 Options specific to PDP11 targets</h4>

  3327. 

  3328. 

  3329. <p>For the pdp11-aout target, three variants of the output format can be

  3330. produced as selected by the following options.  The default variant

  3331. for pdp11-aout is the &lsquo;<samp>--omagic</samp>&rsquo; option, whereas for other

  3332. targets &lsquo;<samp>--nmagic</samp>&rsquo; is the default.  The &lsquo;<samp>--imagic</samp>&rsquo; option is

  3333. defined only for the pdp11-aout target, while the others are described

  3334. here as they apply to the pdp11-aout target.

  3335. </p>

  3336. <dl compact="compact">

  3337. <dd>

  3338. <a name="index-_002dN-1"></a>

  3339. </dd>

  3340. <dt><code>-N</code></dt>

  3341. <dd><a name="index-_002d_002domagic-1"></a>

  3342. </dd>

  3343. <dt><code>--omagic</code></dt>

  3344. <dd>

  3345. <p>Mark the output as <code>OMAGIC</code> (0407) in the <samp>a.out</samp> header to

  3346. indicate that the text segment is not to be write-protected and

  3347. shared.  Since the text and data sections are both readable and

  3348. writable, the data section is allocated immediately contiguous after

  3349. the text segment.  This is the oldest format for PDP11 executable

  3350. programs and is the default for <code>ld</code> on PDP11 Unix systems

  3351. from the beginning through 2.11BSD.

  3352. </p>

  3353. <a name="index-_002dn-1"></a>

  3354. </dd>

  3355. <dt><code>-n</code></dt>

  3356. <dd><a name="index-_002d_002dnmagic-1"></a>

  3357. </dd>

  3358. <dt><code>--nmagic</code></dt>

  3359. <dd>

  3360. <p>Mark the output as <code>NMAGIC</code> (0410) in the <samp>a.out</samp> header to

  3361. indicate that when the output file is executed, the text portion will

  3362. be read-only and shareable among all processes executing the same

  3363. file.  This involves moving the data areas up to the first possible 8K

  3364. byte page boundary following the end of the text.  This option creates

  3365. a <em>pure executable</em> format.

  3366. </p>

  3367. <a name="index-_002dz"></a>

  3368. </dd>

  3369. <dt><code>-z</code></dt>

  3370. <dd><a name="index-_002d_002dimagic"></a>

  3371. </dd>

  3372. <dt><code>--imagic</code></dt>

  3373. <dd>

  3374. <p>Mark the output as <code>IMAGIC</code> (0411) in the <samp>a.out</samp> header to

  3375. indicate that when the output file is executed, the program text and

  3376. data areas will be loaded into separate address spaces using the split

  3377. instruction and data space feature of the memory management unit in

  3378. larger models of the PDP11.  This doubles the address space available

  3379. to the program.  The text segment is again pure, write-protected, and

  3380. shareable.  The only difference in the output format between this

  3381. option and the others, besides the magic number, is that both the text

  3382. and data sections start at location 0.  The &lsquo;<samp>-z</samp>&rsquo; option selected

  3383. this format in 2.11BSD.  This option creates a <em>separate

  3384. executable</em> format.

  3385. </p>

  3386. <a name="index-_002d_002dno_002domagic-1"></a>

  3387. </dd>

  3388. <dt><code>--no-omagic</code></dt>

  3389. <dd>

  3390. <p>Equivalent to &lsquo;<samp>--nmagic</samp>&rsquo; for pdp11-aout.

  3391. </p>

  3392. </dd>

  3393. </dl>

  3394. 

  3395. 

  3396. <hr>

  3397. <div class="header">

  3398. <p>

  3399. Next: <a href="Environment.html#Environment" accesskey="n" rel="next">Environment</a>, Up: <a href="Invocation.html#Invocation" accesskey="u" rel="up">Invocation</a> &nbsp; [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="LD-Index.html#LD-Index" title="Index" rel="index">Index</a>]</p>

  3400. </div>

  3401. 

  3402. 

  3403. 

  3404. </body>

  3405. </html>