| <!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"> |
| <html> |
| <!-- This file documents the GNU Assembler "as". |
| |
| Copyright (C) 1991-2015 Free Software Foundation, Inc. |
| |
| Permission is granted to copy, distribute and/or modify this document |
| under the terms of the GNU Free Documentation License, Version 1.3 |
| or any later version published by the Free Software Foundation; |
| with no Invariant Sections, with no Front-Cover Texts, and with no |
| Back-Cover Texts. A copy of the license is included in the |
| section entitled "GNU Free Documentation License". |
| --> |
| <!-- Created by GNU Texinfo 5.2, http://www.gnu.org/software/texinfo/ --> |
| <head> |
| <title>Using as: Symver</title> |
| |
| <meta name="description" content="Using as: Symver"> |
| <meta name="keywords" content="Using as: Symver"> |
| <meta name="resource-type" content="document"> |
| <meta name="distribution" content="global"> |
| <meta name="Generator" content="makeinfo"> |
| <meta http-equiv="Content-Type" content="text/html; charset=utf-8"> |
| <link href="index.html#Top" rel="start" title="Top"> |
| <link href="AS-Index.html#AS-Index" rel="index" title="AS Index"> |
| <link href="index.html#SEC_Contents" rel="contents" title="Table of Contents"> |
| <link href="Pseudo-Ops.html#Pseudo-Ops" rel="up" title="Pseudo Ops"> |
| <link href="Tag.html#Tag" rel="next" title="Tag"> |
| <link href="SubSection.html#SubSection" rel="prev" title="SubSection"> |
| <style type="text/css"> |
| <!-- |
| a.summary-letter {text-decoration: none} |
| blockquote.smallquotation {font-size: smaller} |
| div.display {margin-left: 3.2em} |
| div.example {margin-left: 3.2em} |
| div.indentedblock {margin-left: 3.2em} |
| div.lisp {margin-left: 3.2em} |
| div.smalldisplay {margin-left: 3.2em} |
| div.smallexample {margin-left: 3.2em} |
| div.smallindentedblock {margin-left: 3.2em; font-size: smaller} |
| div.smalllisp {margin-left: 3.2em} |
| kbd {font-style:oblique} |
| pre.display {font-family: inherit} |
| pre.format {font-family: inherit} |
| pre.menu-comment {font-family: serif} |
| pre.menu-preformatted {font-family: serif} |
| pre.smalldisplay {font-family: inherit; font-size: smaller} |
| pre.smallexample {font-size: smaller} |
| pre.smallformat {font-family: inherit; font-size: smaller} |
| pre.smalllisp {font-size: smaller} |
| span.nocodebreak {white-space:nowrap} |
| span.nolinebreak {white-space:nowrap} |
| span.roman {font-family:serif; font-weight:normal} |
| span.sansserif {font-family:sans-serif; font-weight:normal} |
| ul.no-bullet {list-style: none} |
| --> |
| </style> |
| |
| |
| </head> |
| |
| <body lang="en" bgcolor="#FFFFFF" text="#000000" link="#0000FF" vlink="#800080" alink="#FF0000"> |
| <a name="Symver"></a> |
| <div class="header"> |
| <p> |
| Next: <a href="Tag.html#Tag" accesskey="n" rel="next">Tag</a>, Previous: <a href="SubSection.html#SubSection" accesskey="p" rel="prev">SubSection</a>, Up: <a href="Pseudo-Ops.html#Pseudo-Ops" accesskey="u" rel="up">Pseudo Ops</a> [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="AS-Index.html#AS-Index" title="Index" rel="index">Index</a>]</p> |
| </div> |
| <hr> |
| <a name="g_t_002esymver"></a> |
| <h3 class="section">7.90 <code>.symver</code></h3> |
| <a name="index-symver-directive"></a> |
| <a name="index-symbol-versioning"></a> |
| <a name="index-versions-of-symbols"></a> |
| <p>Use the <code>.symver</code> directive to bind symbols to specific version nodes |
| within a source file. This is only supported on ELF platforms, and is |
| typically used when assembling files to be linked into a shared library. |
| There are cases where it may make sense to use this in objects to be bound |
| into an application itself so as to override a versioned symbol from a |
| shared library. |
| </p> |
| <p>For ELF targets, the <code>.symver</code> directive can be used like this: |
| </p><div class="smallexample"> |
| <pre class="smallexample">.symver <var>name</var>, <var>name2@nodename</var> |
| </pre></div> |
| <p>If the symbol <var>name</var> is defined within the file |
| being assembled, the <code>.symver</code> directive effectively creates a symbol |
| alias with the name <var>name2@nodename</var>, and in fact the main reason that we |
| just don’t try and create a regular alias is that the <var>@</var> character isn’t |
| permitted in symbol names. The <var>name2</var> part of the name is the actual name |
| of the symbol by which it will be externally referenced. The name <var>name</var> |
| itself is merely a name of convenience that is used so that it is possible to |
| have definitions for multiple versions of a function within a single source |
| file, and so that the compiler can unambiguously know which version of a |
| function is being mentioned. The <var>nodename</var> portion of the alias should be |
| the name of a node specified in the version script supplied to the linker when |
| building a shared library. If you are attempting to override a versioned |
| symbol from a shared library, then <var>nodename</var> should correspond to the |
| nodename of the symbol you are trying to override. |
| </p> |
| <p>If the symbol <var>name</var> is not defined within the file being assembled, all |
| references to <var>name</var> will be changed to <var>name2@nodename</var>. If no |
| reference to <var>name</var> is made, <var>name2@nodename</var> will be removed from the |
| symbol table. |
| </p> |
| <p>Another usage of the <code>.symver</code> directive is: |
| </p><div class="smallexample"> |
| <pre class="smallexample">.symver <var>name</var>, <var>name2@@nodename</var> |
| </pre></div> |
| <p>In this case, the symbol <var>name</var> must exist and be defined within |
| the file being assembled. It is similar to <var>name2@nodename</var>. The |
| difference is <var>name2@@nodename</var> will also be used to resolve |
| references to <var>name2</var> by the linker. |
| </p> |
| <p>The third usage of the <code>.symver</code> directive is: |
| </p><div class="smallexample"> |
| <pre class="smallexample">.symver <var>name</var>, <var>name2@@@nodename</var> |
| </pre></div> |
| <p>When <var>name</var> is not defined within the |
| file being assembled, it is treated as <var>name2@nodename</var>. When |
| <var>name</var> is defined within the file being assembled, the symbol |
| name, <var>name</var>, will be changed to <var>name2@@nodename</var>. |
| </p> |
| <hr> |
| <div class="header"> |
| <p> |
| Next: <a href="Tag.html#Tag" accesskey="n" rel="next">Tag</a>, Previous: <a href="SubSection.html#SubSection" accesskey="p" rel="prev">SubSection</a>, Up: <a href="Pseudo-Ops.html#Pseudo-Ops" accesskey="u" rel="up">Pseudo Ops</a> [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="AS-Index.html#AS-Index" title="Index" rel="index">Index</a>]</p> |
| </div> |
| |
| |
| |
| </body> |
| </html> |
