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80 lines
3.1 KiB
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80 lines
3.1 KiB
HTML
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<title>Newlines in Arguments - The C Preprocessor</title>
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<a name="Newlines-in-Arguments"></a>
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<p>
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Previous: <a rel="previous" accesskey="p" href="Argument-Prescan.html#Argument-Prescan">Argument Prescan</a>,
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Up: <a rel="up" accesskey="u" href="Macro-Pitfalls.html#Macro-Pitfalls">Macro Pitfalls</a>
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</div>
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<h4 class="subsection">3.10.7 Newlines in Arguments</h4>
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<p><a name="index-newlines-in-macro-arguments-82"></a>
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The invocation of a function-like macro can extend over many logical
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lines. However, in the present implementation, the entire expansion
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comes out on one line. Thus line numbers emitted by the compiler or
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debugger refer to the line the invocation started on, which might be
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different to the line containing the argument causing the problem.
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<p>Here is an example illustrating this:
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<pre class="smallexample"> #define ignore_second_arg(a,b,c) a; c
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ignore_second_arg (foo (),
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ignored (),
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syntax error);
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</pre>
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<p class="noindent">The syntax error triggered by the tokens <code>syntax error</code> results in
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an error message citing line three—the line of ignore_second_arg—
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even though the problematic code comes from line five.
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<p>We consider this a bug, and intend to fix it in the near future.
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</body></html>
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