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<h3 class="section">Alternate Keywords</h3>
<p><code>-ansi</code> and the various <code>-std</code> options disable certain
keywords. This causes trouble when you want to use GNU C extensions, or
a general-purpose header file that should be usable by all programs,
including ISO C programs. The keywords <code>asm</code>, <code>typeof</code> and
<code>inline</code> are not available in programs compiled with
<code>-ansi</code> or <code>-std</code> (although <code>inline</code> can be used in a
program compiled with <code>-std=c99</code>). The ISO C99 keyword
<code>restrict</code> is only available when <code>-std=gnu99</code> (which will
eventually be the default) or <code>-std=c99</code> (or the equivalent
<code>-std=iso9899:1999</code>) is used.
<p>The way to solve these problems is to put <code>__</code> at the beginning and
end of each problematical keyword. For example, use <code>__asm__</code>
instead of <code>asm</code>, and <code>__inline__</code> instead of <code>inline</code>.
<p>Other C compilers won't accept these alternative keywords; if you want to
compile with another compiler, you can define the alternate keywords as
macros to replace them with the customary keywords. It looks like this:
<pre class="example"> #ifndef __GNUC__
#define __asm__ asm
#endif
</pre>
<p><code>-pedantic</code> and other options cause warnings for many GNU C extensions.
You can
prevent such warnings within one expression by writing
<code>__extension__</code> before the expression. <code>__extension__</code> has no
effect aside from this.
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