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