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<span id="External-Macro-Processors"></span><div class="header">
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Previous: <a href="_0040definfoenclose.html" accesskey="p" rel="prev"><code>@definfoenclose</code></a>, Up: <a href="Defining-New-Texinfo-Commands.html" accesskey="u" rel="up">Defining New Texinfo Commands</a> [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Command-and-Variable-Index.html" title="Index" rel="index">Index</a>]</p>
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<hr>
<span id="External-Macro-Processors_003a-Line-Directives"></span><h3 class="section">17.6 External Macro Processors: Line Directives</h3>
<span id="index-External-macro-processors"></span>
<span id="index-Macro-processors_002c-external"></span>
<p>Texinfo macros (and its other text substitution facilities) work fine
in straightforward cases. If your document needs unusually complex
processing, however, their fragility and limitations can be a problem.
In this case, you may want to use a different macro processor
altogether, such as M4 (see <cite><a href="../m4/index.html#Top">M4</a></cite>) or CPP (see <cite><a href="../cpp/index.html#Top">The C Preprocessor</a></cite>).
</p>
<p>With one exception, Texinfo does not need to know whether its input is
“original” source or preprocessed from some other source file.
Therefore, you can arrange your build system to invoke whatever
programs you like to handle macro expansion or other preprocessing
needs. Texinfo does not offer built-in support for any particular
preprocessor, since no one program seemed likely to suffice for the
requirements of all documents.
</p>
<span id="index-Line-numbers_002c-in-error-messages"></span>
<span id="index-Error-messages_002c-line-numbers-in"></span>
<p>The one exception is line numbers in error messages. In that case,
the line number should refer to the original source file, whatever it
may be. There’s a well-known mechanism for this: the so-called
‘<samp>#line</samp>’ directive. Texinfo supports this.
</p>
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