1<html lang="en"> 2<head> 3<title>Diagnostic Pragmas - Using the GNU Compiler Collection (GCC)</title> 4<meta http-equiv="Content-Type" content="text/html"> 5<meta name="description" content="Using the GNU Compiler Collection (GCC)"> 6<meta name="generator" content="makeinfo 4.13"> 7<link title="Top" rel="start" href="index.html#Top"> 8<link rel="up" href="Pragmas.html#Pragmas" title="Pragmas"> 9<link rel="prev" href="Weak-Pragmas.html#Weak-Pragmas" title="Weak Pragmas"> 10<link rel="next" href="Visibility-Pragmas.html#Visibility-Pragmas" title="Visibility Pragmas"> 11<link href="http://www.gnu.org/software/texinfo/" rel="generator-home" title="Texinfo Homepage"> 12<!-- 13Copyright (C) 1988-2013 Free Software Foundation, Inc. 14 15Permission is granted to copy, distribute and/or modify this document 16under the terms of the GNU Free Documentation License, Version 1.3 or 17any later version published by the Free Software Foundation; with the 18Invariant Sections being ``Funding Free Software'', the Front-Cover 19Texts being (a) (see below), and with the Back-Cover Texts being (b) 20(see below). 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For example, a 60project's policy might require that all sources compile with 61<samp><span class="option">-Werror</span></samp> but certain files might have exceptions allowing 62specific types of warnings. Or, a project might selectively enable 63diagnostics and treat them as errors depending on which preprocessor 64macros are defined. 65 66 <dl> 67<dt><code>#pragma GCC diagnostic </code><var>kind</var> <var>option</var><dd><a name="index-pragma_002c-diagnostic-3481"></a> 68Modifies the disposition of a diagnostic. Note that not all 69diagnostics are modifiable; at the moment only warnings (normally 70controlled by ‘<samp><span class="samp">-W...</span></samp>’) can be controlled, and not all of them. 71Use <samp><span class="option">-fdiagnostics-show-option</span></samp> to determine which diagnostics 72are controllable and which option controls them. 73 74 <p><var>kind</var> is ‘<samp><span class="samp">error</span></samp>’ to treat this diagnostic as an error, 75‘<samp><span class="samp">warning</span></samp>’ to treat it like a warning (even if <samp><span class="option">-Werror</span></samp> is 76in effect), or ‘<samp><span class="samp">ignored</span></samp>’ if the diagnostic is to be ignored. 77<var>option</var> is a double quoted string that matches the command-line 78option. 79 80 <pre class="smallexample"> #pragma GCC diagnostic warning "-Wformat" 81 #pragma GCC diagnostic error "-Wformat" 82 #pragma GCC diagnostic ignored "-Wformat" 83</pre> 84 <p>Note that these pragmas override any command-line options. GCC keeps 85track of the location of each pragma, and issues diagnostics according 86to the state as of that point in the source file. Thus, pragmas occurring 87after a line do not affect diagnostics caused by that line. 88 89 <br><dt><code>#pragma GCC diagnostic push</code><dt><code>#pragma GCC diagnostic pop</code><dd> 90Causes GCC to remember the state of the diagnostics as of each 91<code>push</code>, and restore to that point at each <code>pop</code>. If a 92<code>pop</code> has no matching <code>push</code>, the command-line options are 93restored. 94 95 <pre class="smallexample"> #pragma GCC diagnostic error "-Wuninitialized" 96 foo(a); /* error is given for this one */ 97 #pragma GCC diagnostic push 98 #pragma GCC diagnostic ignored "-Wuninitialized" 99 foo(b); /* no diagnostic for this one */ 100 #pragma GCC diagnostic pop 101 foo(c); /* error is given for this one */ 102 #pragma GCC diagnostic pop 103 foo(d); /* depends on command-line options */ 104</pre> 105 </dl> 106 107 <p>GCC also offers a simple mechanism for printing messages during 108compilation. 109 110 <dl> 111<dt><code>#pragma message </code><var>string</var><dd><a name="index-pragma_002c-diagnostic-3482"></a> 112Prints <var>string</var> as a compiler message on compilation. The message 113is informational only, and is neither a compilation warning nor an error. 114 115 <pre class="smallexample"> #pragma message "Compiling " __FILE__ "..." 116</pre> 117 <p><var>string</var> may be parenthesized, and is printed with location 118information. For example, 119 120 <pre class="smallexample"> #define DO_PRAGMA(x) _Pragma (#x) 121 #define TODO(x) DO_PRAGMA(message ("TODO - " #x)) 122 123 TODO(Remember to fix this) 124</pre> 125 <p class="noindent">prints ‘<samp><span class="samp">/tmp/file.c:4: note: #pragma message: 126TODO - Remember to fix this</span></samp>’. 127 128 </dl> 129 130 </body></html> 131 132