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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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  11. "GNU Free Documentation License".

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  13. (a) The FSF's Front-Cover Text is:

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  15. A GNU Manual

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  23. <head>

  24. <meta http-equiv="Content-Type" content="text/html; charset=utf-8">

  25. <title>GGC Roots (GNU Compiler Collection (GCC) Internals)</title>

  26. 

  27. <meta name="description" content="GGC Roots (GNU Compiler Collection (GCC) Internals)">

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

  33. <link href="Option-Index.html#Option-Index" rel="index" title="Option Index">

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

  35. <link href="Type-Information.html#Type-Information" rel="up" title="Type Information">

  36. <link href="Files.html#Files" rel="next" title="Files">

  37. <link href="User-GC.html#User-GC" rel="prev" title="User GC">

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  69. <body lang="en">

  70. <a name="GGC-Roots"></a>

  71. <div class="header">

  72. <p>

  73. Next: <a href="Files.html#Files" accesskey="n" rel="next">Files</a>, Previous: <a href="User-GC.html#User-GC" accesskey="p" rel="prev">User GC</a>, Up: <a href="Type-Information.html#Type-Information" accesskey="u" rel="up">Type Information</a> &nbsp; [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Option-Index.html#Option-Index" title="Index" rel="index">Index</a>]</p>

  74. </div>

  75. <hr>

  76. <a name="Marking-Roots-for-the-Garbage-Collector"></a>

  77. <h3 class="section">23.4 Marking Roots for the Garbage Collector</h3>

  78. <a name="index-roots_002c-marking"></a>

  79. <a name="index-marking-roots"></a>

  80. 

  81. <p>In addition to keeping track of types, the type machinery also locates

  82. the global variables (<em>roots</em>) that the garbage collector starts

  83. at.  Roots must be declared using one of the following syntaxes:

  84. </p>

  85. <ul>

  86. <li> <code>extern GTY(([<var>options</var>])) <var>type</var> <var>name</var>;</code>

  87. </li><li> <code>static GTY(([<var>options</var>])) <var>type</var> <var>name</var>;</code>

  88. </li></ul>

  89. <p>The syntax

  90. </p><ul>

  91. <li> <code>GTY(([<var>options</var>])) <var>type</var> <var>name</var>;</code>

  92. </li></ul>

  93. <p>is <em>not</em> accepted.  There should be an <code>extern</code> declaration

  94. of such a variable in a header somewhere&mdash;mark that, not the

  95. definition.  Or, if the variable is only used in one file, make it

  96. <code>static</code>.

  97. </p>

  98. 

  99. 

  100. 

  101. </body>

  102. </html>