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<title>Using the GNU Compiler Collection (GCC): Asm Labels</title>
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<p>
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Next: <a href="Explicit-Register-Variables.html#Explicit-Register-Variables" accesskey="n" rel="next">Explicit Register Variables</a>, Previous: <a href="Constraints.html#Constraints" accesskey="p" rel="prev">Constraints</a>, Up: <a href="Using-Assembly-Language-with-C.html#Using-Assembly-Language-with-C" accesskey="u" rel="up">Using Assembly Language with C</a> [<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>
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<hr>
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<a name="Controlling-Names-Used-in-Assembler-Code"></a>
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<h4 class="subsection">6.44.4 Controlling Names Used in Assembler Code</h4>
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<a name="index-assembler-names-for-identifiers"></a>
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<a name="index-names-used-in-assembler-code"></a>
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<a name="index-identifiers_002c-names-in-assembler-code"></a>
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<p>You can specify the name to be used in the assembler code for a C
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function or variable by writing the <code>asm</code> (or <code>__asm__</code>)
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keyword after the declarator.
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It is up to you to make sure that the assembler names you choose do not
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conflict with any other assembler symbols, or reference registers.
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</p>
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<a name="Assembler-names-for-data_003a"></a>
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<h4 class="subsubheading">Assembler names for data:</h4>
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<p>This sample shows how to specify the assembler name for data:
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</p>
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<div class="smallexample">
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<pre class="smallexample">int foo asm ("myfoo") = 2;
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</pre></div>
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<p>This specifies that the name to be used for the variable <code>foo</code> in
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the assembler code should be ‘<samp>myfoo</samp>’ rather than the usual
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‘<samp>_foo</samp>’.
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</p>
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<p>On systems where an underscore is normally prepended to the name of a C
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variable, this feature allows you to define names for the
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linker that do not start with an underscore.
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</p>
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<p>GCC does not support using this feature with a non-static local variable
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since such variables do not have assembler names. If you are
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trying to put the variable in a particular register, see
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<a href="Explicit-Register-Variables.html#Explicit-Register-Variables">Explicit Register Variables</a>.
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</p>
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<a name="Assembler-names-for-functions_003a"></a>
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<h4 class="subsubheading">Assembler names for functions:</h4>
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<p>To specify the assembler name for functions, write a declaration for the
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function before its definition and put <code>asm</code> there, like this:
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</p>
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<div class="smallexample">
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<pre class="smallexample">int func (int x, int y) asm ("MYFUNC");
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int func (int x, int y)
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{
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/* <span class="roman">…</span> */
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</pre></div>
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<p>This specifies that the name to be used for the function <code>func</code> in
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the assembler code should be <code>MYFUNC</code>.
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</p>
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<hr>
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<div class="header">
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<p>
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Next: <a href="Explicit-Register-Variables.html#Explicit-Register-Variables" accesskey="n" rel="next">Explicit Register Variables</a>, Previous: <a href="Constraints.html#Constraints" accesskey="p" rel="prev">Constraints</a>, Up: <a href="Using-Assembly-Language-with-C.html#Using-Assembly-Language-with-C" accesskey="u" rel="up">Using Assembly Language with C</a> [<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>
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