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| 3 | <!-- Copyright (C) 2022 Richard Stallman and Free Software Foundation, Inc.
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| 4 |
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| 5 | (The work of Trevis Rothwell and Nelson Beebe has been assigned or
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| 6 | licensed to the FSF.)
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| 7 |
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| 8 | Permission is granted to copy, distribute and/or modify this document
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| 9 | under the terms of the GNU Free Documentation License, Version 1.3 or
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| 12 | Front-Cover Texts being "A GNU Manual," and with the Back-Cover
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| 20 | <head>
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| 21 | <meta http-equiv="Content-Type" content="text/html; charset=utf-8">
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| 22 | <title>Diagnostics (GNU C Language Manual)</title>
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| 23 |
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| 24 | <meta name="description" content="Diagnostics (GNU C Language Manual)">
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| 25 | <meta name="keywords" content="Diagnostics (GNU C Language Manual)">
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| 30 | <link href="Symbol-Index.html" rel="index" title="Symbol Index">
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| 31 | <link href="index.html#SEC_Contents" rel="contents" title="Table of Contents">
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| 32 | <link href="Preprocessing.html" rel="up" title="Preprocessing">
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| 33 | <link href="Line-Control.html" rel="next" title="Line Control">
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| 54 |
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| 55 | </head>
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| 56 |
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| 57 | <body lang="en">
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| 58 | <span id="Diagnostics"></span><div class="header">
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| 59 | <p>
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| 60 | Next: <a href="Line-Control.html" accesskey="n" rel="next">Line Control</a>, Previous: <a href="Conditionals.html" accesskey="p" rel="prev">Conditionals</a>, Up: <a href="Preprocessing.html" accesskey="u" rel="up">Preprocessing</a> [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Symbol-Index.html" title="Index" rel="index">Index</a>]</p>
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| 61 | </div>
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| 62 | <hr>
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| 63 | <span id="Diagnostics-1"></span><h3 class="section">26.7 Diagnostics</h3>
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| 64 | <span id="index-diagnostic"></span>
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| 65 | <span id="index-reporting-errors"></span>
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| 66 | <span id="index-reporting-warnings"></span>
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| 67 |
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| 68 | <span id="index-_0023error"></span>
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| 69 | <p>The directive <code>#error</code> reports a fatal error. The
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| 70 | tokens forming the rest of the line following <code>#error</code> are used
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| 71 | as the error message.
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| 72 | </p>
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| 73 | <p>The usual place to use <code>#error</code> is inside a conditional that
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| 74 | detects a combination of parameters that you know the program does not
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| 75 | properly support. For example,
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| 76 | </p>
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| 77 | <div class="example">
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| 78 | <pre class="example">#if !defined(UNALIGNED_INT_ASM_OP) && defined(DWARF2_DEBUGGING_INFO)
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| 79 | #error "DWARF2_DEBUGGING_INFO requires UNALIGNED_INT_ASM_OP."
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| 80 | #endif
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| 81 | </pre></div>
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| 82 |
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| 83 | <span id="index-_0023warning"></span>
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| 84 | <p>The directive <code>#warning</code> is like <code>#error</code>, but it reports a
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| 85 | warning instead of an error. The tokens following <code>#warning</code> are
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| 86 | used as the warning message.
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| 87 | </p>
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| 88 | <p>You might use <code>#warning</code> in obsolete header files, with a message
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| 89 | saying which header file to use instead.
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| 90 | </p>
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| 91 | <p>Neither <code>#error</code> nor <code>#warning</code> macro-expands its argument.
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| 92 | Internal whitespace sequences are each replaced with a single space.
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| 93 | The line must consist of complete tokens. It is wisest to make the
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| 94 | argument of these directives be a single string constant; this avoids
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| 95 | problems with apostrophes and the like.
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| 96 | </p>
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| 97 |
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| 98 |
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| 99 |
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| 100 | </body>
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| 101 | </html>
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