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toolchain-gcc-arm-embedded/share/doc/gcc-arm-none-eabi/html/stabs/Statics.html

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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>

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  14. <head>

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  16. <title>Statics (STABS)</title>

  17. 

  18. <meta name="description" content="Statics (STABS)">

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  23. <link href="index.html#Top" rel="start" title="Top">

  24. <link href="Symbol-Types-Index.html#Symbol-Types-Index" rel="index" title="Symbol Types Index">

  25. <link href="index.html#SEC_Contents" rel="contents" title="Table of Contents">

  26. <link href="Variables.html#Variables" rel="up" title="Variables">

  27. <link href="Based-Variables.html#Based-Variables" rel="next" title="Based Variables">

  28. <link href="Common-Blocks.html#Common-Blocks" rel="prev" title="Common Blocks">

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  59. 

  60. <body lang="en">

  61. <a name="Statics"></a>

  62. <div class="header">

  63. <p>

  64. Next: <a href="Based-Variables.html#Based-Variables" accesskey="n" rel="next">Based Variables</a>, Previous: <a href="Common-Blocks.html#Common-Blocks" accesskey="p" rel="prev">Common Blocks</a>, Up: <a href="Variables.html#Variables" accesskey="u" rel="up">Variables</a> &nbsp; [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Symbol-Types-Index.html#Symbol-Types-Index" title="Index" rel="index">Index</a>]</p>

  65. </div>

  66. <hr>

  67. <a name="Static-Variables"></a>

  68. <h3 class="section">4.5 Static Variables</h3>

  69. 

  70. <p>Initialized static variables are represented by the &lsquo;<samp>S</samp>&rsquo; and

  71. &lsquo;<samp>V</samp>&rsquo; symbol descriptors.  &lsquo;<samp>S</samp>&rsquo; means file scope static, and

  72. &lsquo;<samp>V</samp>&rsquo; means procedure scope static.  One exception: in XCOFF, IBM&rsquo;s

  73. xlc compiler always uses &lsquo;<samp>V</samp>&rsquo;, and whether it is file scope or not

  74. is distinguished by whether the stab is located within a function.

  75. </p>

  76. <a name="index-N_005fSTSYM"></a>

  77. <a name="index-N_005fLCSYM"></a>

  78. <a name="index-N_005fFUN_002c-for-variables"></a>

  79. <a name="index-N_005fROSYM"></a>

  80. <p>In a.out files, <code>N_STSYM</code> means the data section, <code>N_FUN</code>

  81. means the text section, and <code>N_LCSYM</code> means the bss section.  For

  82. those systems with a read-only data section separate from the text

  83. section (Solaris), <code>N_ROSYM</code> means the read-only data section.

  84. </p>

  85. <p>For example, the source lines:

  86. </p>

  87. <div class="example">

  88. <pre class="example">static const int var_const = 5;

  89. static int var_init = 2;

  90. static int var_noinit;

  91. </pre></div>

  92. 

  93. <p>yield the following stabs:

  94. </p>

  95. <div class="example">

  96. <pre class="example">.stabs &quot;var_const:S1&quot;,36,0,0,_var_const      # <span class="roman">36 is N_FUN</span>

  97. &hellip;

  98. .stabs &quot;var_init:S1&quot;,38,0,0,_var_init        # <span class="roman">38 is N_STSYM</span>

  99. &hellip;

  100. .stabs &quot;var_noinit:S1&quot;,40,0,0,_var_noinit    # <span class="roman">40 is N_LCSYM</span>

  101. </pre></div>

  102. 

  103. <a name="index-C_005fSTSYM"></a>

  104. <a name="index-C_005fBSTAT"></a>

  105. <a name="index-C_005fESTAT"></a>

  106. <p>In XCOFF files, the stab type need not indicate the section;

  107. <code>C_STSYM</code> can be used for all statics.  Also, each static variable

  108. is enclosed in a static block.  A <code>C_BSTAT</code> (emitted with a

  109. &lsquo;<samp>.bs</samp>&rsquo; assembler directive) symbol begins the static block; its

  110. value is the symbol number of the csect symbol whose value is the

  111. address of the static block, its section is the section of the variables

  112. in that static block, and its name is &lsquo;<samp>.bs</samp>&rsquo;.  A <code>C_ESTAT</code>

  113. (emitted with a &lsquo;<samp>.es</samp>&rsquo; assembler directive) symbol ends the static

  114. block; its name is &lsquo;<samp>.es</samp>&rsquo; and its value and section are ignored.

  115. </p>

  116. <p>In ECOFF files, the storage class is used to specify the section, so the

  117. stab type need not indicate the section.

  118. </p>

  119. <p>In ELF files, for the SunPRO compiler version 2.0.1, symbol descriptor

  120. &lsquo;<samp>S</samp>&rsquo; means that the address is absolute (the linker relocates it)

  121. and symbol descriptor &lsquo;<samp>V</samp>&rsquo; means that the address is relative to the

  122. start of the relevant section for that compilation unit.  SunPRO has

  123. plans to have the linker stop relocating stabs; I suspect that their the

  124. debugger gets the address from the corresponding ELF (not stab) symbol.

  125. I&rsquo;m not sure how to find which symbol of that name is the right one.

  126. The clean way to do all this would be to have the value of a symbol

  127. descriptor &lsquo;<samp>S</samp>&rsquo; symbol be an offset relative to the start of the

  128. file, just like everything else, but that introduces obvious

  129. compatibility problems.  For more information on linker stab relocation,

  130. See <a href="ELF-Linker-Relocation.html#ELF-Linker-Relocation">ELF Linker Relocation</a>.

  131. </p>

  132. <hr>

  133. <div class="header">

  134. <p>

  135. Next: <a href="Based-Variables.html#Based-Variables" accesskey="n" rel="next">Based Variables</a>, Previous: <a href="Common-Blocks.html#Common-Blocks" accesskey="p" rel="prev">Common Blocks</a>, Up: <a href="Variables.html#Variables" accesskey="u" rel="up">Variables</a> &nbsp; [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Symbol-Types-Index.html#Symbol-Types-Index" title="Index" rel="index">Index</a>]</p>

  136. </div>

  137. 

  138. 

  139. 

  140. </body>

  141. </html>