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| <h4 class="subsection">1.2.1 ISO C</h4> |
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| <p><a name="index-ISO-C-3"></a> |
| The GNU C library is compatible with the C standard adopted by the |
| American National Standards Institute (ANSI): |
| <cite>American National Standard X3.159-1989—“ANSI C”</cite> and later |
| by the International Standardization Organization (ISO): |
| <cite>ISO/IEC 9899:1990, “Programming languages—C”</cite>. |
| We here refer to the standard as ISO C<!-- /@w --> since this is the more |
| general standard in respect of ratification. |
| The header files and library facilities that make up the GNU library are |
| a superset of those specified by the ISO C<!-- /@w --> standard. |
| |
| <p><a name="index-gcc-4"></a>If you are concerned about strict adherence to the ISO C<!-- /@w --> standard, you |
| should use the ‘<samp><span class="samp">-ansi</span></samp>’ option when you compile your programs with |
| the GNU C compiler. This tells the compiler to define <em>only</em> ISO |
| standard features from the library header files, unless you explicitly |
| ask for additional features. See <a href="Feature-Test-Macros.html#Feature-Test-Macros">Feature Test Macros</a>, for |
| information on how to do this. |
| |
| <p>Being able to restrict the library to include only ISO C<!-- /@w --> features is |
| important because ISO C<!-- /@w --> puts limitations on what names can be defined |
| by the library implementation, and the GNU extensions don't fit these |
| limitations. See <a href="Reserved-Names.html#Reserved-Names">Reserved Names</a>, for more information about these |
| restrictions. |
| |
| <p>This manual does not attempt to give you complete details on the |
| differences between ISO C<!-- /@w --> and older dialects. It gives advice on how |
| to write programs to work portably under multiple C dialects, but does |
| not aim for completeness. |
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