109 lines
4.4 KiB
HTML
109 lines
4.4 KiB
HTML
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<title>The C Preprocessor: Newlines in Arguments</title>
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<a name="Newlines-in-Arguments"></a>
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<p>
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Previous: <a href="Argument-Prescan.html#Argument-Prescan" accesskey="p" rel="prev">Argument Prescan</a>, Up: <a href="Macro-Pitfalls.html#Macro-Pitfalls" accesskey="u" rel="up">Macro Pitfalls</a> [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Index-of-Directives.html#Index-of-Directives" title="Index" rel="index">Index</a>]</p>
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</div>
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<hr>
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<a name="Newlines-in-Arguments-1"></a>
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<h4 class="subsection">3.10.7 Newlines in Arguments</h4>
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<a name="index-newlines-in-macro-arguments"></a>
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<p>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>
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<p>Here is an example illustrating this:
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</p>
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<div class="smallexample">
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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></div>
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<p>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>
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<p>We consider this a bug, and intend to fix it in the near future.
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</p>
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