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| <h2 class="chapter">8 Other Directives</h2> |
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| <p><a name="index-g_t_0023ident-104"></a><a name="index-g_t_0023sccs-105"></a>The ‘<samp><span class="samp">#ident</span></samp>’ directive takes one argument, a string constant. On |
| some systems, that string constant is copied into a special segment of |
| the object file. On other systems, the directive is ignored. The |
| ‘<samp><span class="samp">#sccs</span></samp>’ directive is a synonym for ‘<samp><span class="samp">#ident</span></samp>’. |
| |
| <p>These directives are not part of the C standard, but they are not |
| official GNU extensions either. What historical information we have |
| been able to find, suggests they originated with System V. |
| |
| <p><a name="index-null-directive-106"></a>The <dfn>null directive</dfn> consists of a ‘<samp><span class="samp">#</span></samp>’ followed by a newline, |
| with only whitespace (including comments) in between. A null directive |
| is understood as a preprocessing directive but has no effect on the |
| preprocessor output. The primary significance of the existence of the |
| null directive is that an input line consisting of just a ‘<samp><span class="samp">#</span></samp>’ will |
| produce no output, rather than a line of output containing just a |
| ‘<samp><span class="samp">#</span></samp>’. Supposedly some old C programs contain such lines. |
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