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| <title>The C Preprocessor: Newlines in Arguments</title> |
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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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| <a name="Newlines-in-Arguments-1"></a> |
| <h4 class="subsection">3.10.7 Newlines in Arguments</h4> |
| <a name="index-newlines-in-macro-arguments"></a> |
| |
| <p>The invocation of a function-like macro can extend over many logical |
| lines. However, in the present implementation, the entire expansion |
| comes out on one line. Thus line numbers emitted by the compiler or |
| debugger refer to the line the invocation started on, which might be |
| different to the line containing the argument causing the problem. |
| </p> |
| <p>Here is an example illustrating this: |
| </p> |
| <div class="smallexample"> |
| <pre class="smallexample">#define ignore_second_arg(a,b,c) a; c |
| |
| ignore_second_arg (foo (), |
| ignored (), |
| syntax error); |
| </pre></div> |
| |
| <p>The syntax error triggered by the tokens <code>syntax error</code> results in |
| an error message citing line three—the line of ignore_second_arg— |
| even though the problematic code comes from line five. |
| </p> |
| <p>We consider this a bug, and intend to fix it in the near future. |
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