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178 lines
7.5 KiB
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<head>
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<title>Diagnostic Pragmas (Using the GNU Compiler Collection (GCC))</title>
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<link href="index.html#Top" rel="start" title="Top">
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<link href="Option-Index.html#Option-Index" rel="index" title="Option Index">
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<link href="index.html#SEC_Contents" rel="contents" title="Table of Contents">
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<link href="Pragmas.html#Pragmas" rel="up" title="Pragmas">
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<link href="Visibility-Pragmas.html#Visibility-Pragmas" rel="next" title="Visibility Pragmas">
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<link href="Weak-Pragmas.html#Weak-Pragmas" rel="prev" title="Weak Pragmas">
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</head>
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<a name="Diagnostic-Pragmas"></a>
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<div class="header">
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<p>
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Next: <a href="Visibility-Pragmas.html#Visibility-Pragmas" accesskey="n" rel="next">Visibility Pragmas</a>, Previous: <a href="Weak-Pragmas.html#Weak-Pragmas" accesskey="p" rel="prev">Weak Pragmas</a>, Up: <a href="Pragmas.html#Pragmas" accesskey="u" rel="up">Pragmas</a> [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Option-Index.html#Option-Index" title="Index" rel="index">Index</a>]</p>
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</div>
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<hr>
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<a name="Diagnostic-Pragmas-1"></a>
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<h4 class="subsection">6.61.12 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>-Werror</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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</p>
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<dl compact="compact">
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<dt><code>#pragma GCC diagnostic <var>kind</var> <var>option</var></code></dt>
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<dd><a name="index-pragma_002c-diagnostic"></a>
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<p>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>-W…</samp>’) can be controlled, and not all of them.
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Use <samp>-fdiagnostics-show-option</samp> to determine which diagnostics
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are controllable and which option controls them.
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</p>
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<p><var>kind</var> is ‘<samp>error</samp>’ to treat this diagnostic as an error,
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‘<samp>warning</samp>’ to treat it like a warning (even if <samp>-Werror</samp> is
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in effect), or ‘<samp>ignored</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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</p>
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<div class="smallexample">
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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></div>
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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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</p>
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</dd>
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<dt><code>#pragma GCC diagnostic push</code></dt>
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<dt><code>#pragma GCC diagnostic pop</code></dt>
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<dd>
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<p>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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</p>
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<div class="smallexample">
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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></div>
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</dd>
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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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</p>
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<dl compact="compact">
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<dt><code>#pragma message <var>string</var></code></dt>
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<dd><a name="index-pragma_002c-diagnostic-1"></a>
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<p>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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</p>
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<div class="smallexample">
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<pre class="smallexample">#pragma message "Compiling " __FILE__ "..."
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</pre></div>
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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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</p>
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<div class="smallexample">
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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></div>
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<p>prints ‘<samp>/tmp/file.c:4: note: #pragma message:
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TODO - Remember to fix this</samp>’.
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</p>
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</dd>
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</dl>
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<hr>
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<div class="header">
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<p>
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Next: <a href="Visibility-Pragmas.html#Visibility-Pragmas" accesskey="n" rel="next">Visibility Pragmas</a>, Previous: <a href="Weak-Pragmas.html#Weak-Pragmas" accesskey="p" rel="prev">Weak Pragmas</a>, Up: <a href="Pragmas.html#Pragmas" accesskey="u" rel="up">Pragmas</a> [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Option-Index.html#Option-Index" title="Index" rel="index">Index</a>]</p>
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</div>
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</body>
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