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131 lines
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131 lines
6.0 KiB
HTML
4 years ago
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<html lang="en">
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<title>Diagnostic Pragmas - Using the GNU Compiler Collection (GCC)</title>
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<meta name="description" content="Using the GNU Compiler Collection (GCC)">
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<link title="Top" rel="start" href="index.html#Top">
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<link rel="up" href="Pragmas.html#Pragmas" title="Pragmas">
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<link rel="prev" href="Weak-Pragmas.html#Weak-Pragmas" title="Weak Pragmas">
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<link rel="next" href="Visibility-Pragmas.html#Visibility-Pragmas" title="Visibility Pragmas">
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<link href="http://www.gnu.org/software/texinfo/" rel="generator-home" title="Texinfo Homepage">
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Copyright (C) 1988-2015 Free Software Foundation, Inc.
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Permission is granted to copy, distribute and/or modify this document
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under the terms of the GNU Free Documentation License, Version 1.3 or
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any later version published by the Free Software Foundation; with the
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Invariant Sections being ``Funding Free Software'', the Front-Cover
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(see below). A copy of the license is included in the section entitled
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``GNU Free Documentation License''.
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(a) The FSF's Front-Cover Text is:
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A GNU Manual
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(b) The FSF's Back-Cover Text is:
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You have freedom to copy and modify this GNU Manual, like GNU
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</head>
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<body>
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<div class="node">
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<a name="Diagnostic-Pragmas"></a>
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<p>
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Next: <a rel="next" accesskey="n" href="Visibility-Pragmas.html#Visibility-Pragmas">Visibility Pragmas</a>,
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Previous: <a rel="previous" accesskey="p" href="Weak-Pragmas.html#Weak-Pragmas">Weak Pragmas</a>,
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Up: <a rel="up" accesskey="u" href="Pragmas.html#Pragmas">Pragmas</a>
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<hr>
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</div>
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<h4 class="subsection">6.60.10 Diagnostic Pragmas</h4>
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<p>GCC allows the user to selectively enable or disable certain types of
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diagnostics, and change the kind of the diagnostic. For example, a
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project's policy might require that all sources compile with
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<samp><span class="option">-Werror</span></samp> but certain files might have exceptions allowing
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specific types of warnings. Or, a project might selectively enable
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diagnostics and treat them as errors depending on which preprocessor
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macros are defined.
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<dl>
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<dt><code>#pragma GCC diagnostic </code><var>kind</var> <var>option</var><dd><a name="index-pragma_002c-diagnostic-4178"></a>
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Modifies the disposition of a diagnostic. Note that not all
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diagnostics are modifiable; at the moment only warnings (normally
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controlled by ‘<samp><span class="samp">-W...</span></samp>’) can be controlled, and not all of them.
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Use <samp><span class="option">-fdiagnostics-show-option</span></samp> to determine which diagnostics
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are controllable and which option controls them.
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<p><var>kind</var> is ‘<samp><span class="samp">error</span></samp>’ to treat this diagnostic as an error,
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‘<samp><span class="samp">warning</span></samp>’ to treat it like a warning (even if <samp><span class="option">-Werror</span></samp> is
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in effect), or ‘<samp><span class="samp">ignored</span></samp>’ if the diagnostic is to be ignored.
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<var>option</var> is a double quoted string that matches the command-line
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option.
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<pre class="smallexample"> #pragma GCC diagnostic warning "-Wformat"
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#pragma GCC diagnostic error "-Wformat"
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#pragma GCC diagnostic ignored "-Wformat"
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</pre>
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<p>Note that these pragmas override any command-line options. GCC keeps
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track of the location of each pragma, and issues diagnostics according
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to the state as of that point in the source file. Thus, pragmas occurring
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after a line do not affect diagnostics caused by that line.
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<br><dt><code>#pragma GCC diagnostic push</code><dt><code>#pragma GCC diagnostic pop</code><dd>
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Causes GCC to remember the state of the diagnostics as of each
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<code>push</code>, and restore to that point at each <code>pop</code>. If a
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<code>pop</code> has no matching <code>push</code>, the command-line options are
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restored.
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<pre class="smallexample"> #pragma GCC diagnostic error "-Wuninitialized"
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foo(a); /* error is given for this one */
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#pragma GCC diagnostic push
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#pragma GCC diagnostic ignored "-Wuninitialized"
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foo(b); /* no diagnostic for this one */
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#pragma GCC diagnostic pop
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foo(c); /* error is given for this one */
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#pragma GCC diagnostic pop
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foo(d); /* depends on command-line options */
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</pre>
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</dl>
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<p>GCC also offers a simple mechanism for printing messages during
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compilation.
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<dl>
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<dt><code>#pragma message </code><var>string</var><dd><a name="index-pragma_002c-diagnostic-4179"></a>
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Prints <var>string</var> as a compiler message on compilation. The message
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is informational only, and is neither a compilation warning nor an error.
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<pre class="smallexample"> #pragma message "Compiling " __FILE__ "..."
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</pre>
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<p><var>string</var> may be parenthesized, and is printed with location
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information. For example,
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<pre class="smallexample"> #define DO_PRAGMA(x) _Pragma (#x)
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#define TODO(x) DO_PRAGMA(message ("TODO - " #x))
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TODO(Remember to fix this)
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</pre>
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<p class="noindent">prints ‘<samp><span class="samp">/tmp/file.c:4: note: #pragma message:
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TODO - Remember to fix this</span></samp>’.
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</dl>
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</body></html>
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