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<title>Using the GNU Compiler Collection (GCC): Variable Attributes</title>
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Next: <a href="Type-Attributes.html#Type-Attributes" accesskey="n" rel="next">Type Attributes</a>, Previous: <a href="Function-Attributes.html#Function-Attributes" accesskey="p" rel="previous">Function Attributes</a>, Up: <a href="C-Extensions.html#C-Extensions" accesskey="u" rel="up">C Extensions</a> [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Indices.html#Indices" title="Index" rel="index">Index</a>]</p>
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<a name="Specifying-Attributes-of-Variables"></a>
<h3 class="section">6.34 Specifying Attributes of Variables</h3>
<a name="index-attribute-of-variables"></a>
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<p>The keyword <code>__attribute__</code> allows you to specify special properties
of variables, function parameters, or structure, union, and, in C++, class
members. This <code>__attribute__</code> keyword is followed by an attribute
specification enclosed in double parentheses. Some attributes are currently
defined generically for variables. Other attributes are defined for
variables on particular target systems. Other attributes are available
for functions (see <a href="Function-Attributes.html#Function-Attributes">Function Attributes</a>), labels (see <a href="Label-Attributes.html#Label-Attributes">Label Attributes</a>),
enumerators (see <a href="Enumerator-Attributes.html#Enumerator-Attributes">Enumerator Attributes</a>), statements
(see <a href="Statement-Attributes.html#Statement-Attributes">Statement Attributes</a>), and for types (see <a href="Type-Attributes.html#Type-Attributes">Type Attributes</a>).
Other front ends might define more attributes
(see <a href="C_002b_002b-Extensions.html#C_002b_002b-Extensions">Extensions to the C++ Language</a>).
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<p>See <a href="Attribute-Syntax.html#Attribute-Syntax">Attribute Syntax</a>, for details of the exact syntax for using
attributes.
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<table class="menu" border="0" cellspacing="0">
<tr><td align="left" valign="top">• <a href="Common-Variable-Attributes.html#Common-Variable-Attributes" accesskey="1">Common Variable Attributes</a>:</td><td> </td><td align="left" valign="top">
</td></tr>
<tr><td align="left" valign="top">• <a href="ARC-Variable-Attributes.html#ARC-Variable-Attributes" accesskey="2">ARC Variable Attributes</a>:</td><td> </td><td align="left" valign="top">
</td></tr>
<tr><td align="left" valign="top">• <a href="AVR-Variable-Attributes.html#AVR-Variable-Attributes" accesskey="3">AVR Variable Attributes</a>:</td><td> </td><td align="left" valign="top">
</td></tr>
<tr><td align="left" valign="top">• <a href="Blackfin-Variable-Attributes.html#Blackfin-Variable-Attributes" accesskey="4">Blackfin Variable Attributes</a>:</td><td> </td><td align="left" valign="top">
</td></tr>
<tr><td align="left" valign="top">• <a href="H8_002f300-Variable-Attributes.html#H8_002f300-Variable-Attributes" accesskey="5">H8/300 Variable Attributes</a>:</td><td> </td><td align="left" valign="top">
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<tr><td align="left" valign="top">• <a href="IA_002d64-Variable-Attributes.html#IA_002d64-Variable-Attributes" accesskey="6">IA-64 Variable Attributes</a>:</td><td> </td><td align="left" valign="top">
</td></tr>
<tr><td align="left" valign="top">• <a href="LoongArch-Variable-Attributes.html#LoongArch-Variable-Attributes" accesskey="7">LoongArch Variable Attributes</a>:</td><td> </td><td align="left" valign="top">
</td></tr>
<tr><td align="left" valign="top">• <a href="M32R_002fD-Variable-Attributes.html#M32R_002fD-Variable-Attributes" accesskey="8">M32R/D Variable Attributes</a>:</td><td> </td><td align="left" valign="top">
</td></tr>
<tr><td align="left" valign="top">• <a href="Microsoft-Windows-Variable-Attributes.html#Microsoft-Windows-Variable-Attributes" accesskey="9">Microsoft Windows Variable Attributes</a>:</td><td> </td><td align="left" valign="top">
</td></tr>
<tr><td align="left" valign="top">• <a href="MSP430-Variable-Attributes.html#MSP430-Variable-Attributes">MSP430 Variable Attributes</a>:</td><td> </td><td align="left" valign="top">
</td></tr>
<tr><td align="left" valign="top">• <a href="Nvidia-PTX-Variable-Attributes.html#Nvidia-PTX-Variable-Attributes">Nvidia PTX Variable Attributes</a>:</td><td> </td><td align="left" valign="top">
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<tr><td align="left" valign="top">• <a href="PowerPC-Variable-Attributes.html#PowerPC-Variable-Attributes">PowerPC Variable Attributes</a>:</td><td> </td><td align="left" valign="top">
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<tr><td align="left" valign="top">• <a href="RL78-Variable-Attributes.html#RL78-Variable-Attributes">RL78 Variable Attributes</a>:</td><td> </td><td align="left" valign="top">
</td></tr>
<tr><td align="left" valign="top">• <a href="V850-Variable-Attributes.html#V850-Variable-Attributes">V850 Variable Attributes</a>:</td><td> </td><td align="left" valign="top">
</td></tr>
<tr><td align="left" valign="top">• <a href="x86-Variable-Attributes.html#x86-Variable-Attributes">x86 Variable Attributes</a>:</td><td> </td><td align="left" valign="top">
</td></tr>
<tr><td align="left" valign="top">• <a href="Xstormy16-Variable-Attributes.html#Xstormy16-Variable-Attributes">Xstormy16 Variable Attributes</a>:</td><td> </td><td align="left" valign="top">
</td></tr>
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