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85 lines
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<a name="Traditional-miscellany"></a>
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<p>
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Next: <a rel="next" accesskey="n" href="Traditional-warnings.html#Traditional-warnings">Traditional warnings</a>,
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Previous: <a rel="previous" accesskey="p" href="Traditional-macros.html#Traditional-macros">Traditional macros</a>,
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Up: <a rel="up" accesskey="u" href="Traditional-Mode.html#Traditional-Mode">Traditional Mode</a>
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<h3 class="section">10.3 Traditional miscellany</h3>
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<p>Here are some things to be aware of when using the traditional
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preprocessor.
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<ul>
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<li>Preprocessing directives are recognized only when their leading
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‘<samp><span class="samp">#</span></samp>’ appears in the first column. There can be no whitespace
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between the beginning of the line and the ‘<samp><span class="samp">#</span></samp>’, but whitespace can
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follow the ‘<samp><span class="samp">#</span></samp>’.
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<li>A true traditional C preprocessor does not recognize ‘<samp><span class="samp">#error</span></samp>’ or
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‘<samp><span class="samp">#pragma</span></samp>’, and may not recognize ‘<samp><span class="samp">#elif</span></samp>’. CPP supports all
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the directives in traditional mode that it supports in ISO mode,
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including extensions, with the exception that the effects of
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‘<samp><span class="samp">#pragma GCC poison</span></samp>’ are undefined.
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<li>__STDC__ is not defined.
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<li>If you use digraphs the behavior is undefined.
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<li>If a line that looks like a directive appears within macro arguments,
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the behavior is undefined.
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</ul>
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