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, 1989, 1992, 1993, 1994, 1995, 1996, 1997, 141998, 1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009, 152010 Free Software Foundation, Inc. 16 17Permission is granted to copy, distribute and/or modify this document 18under the terms of the GNU Free Documentation License, Version 1.3 or 19any later version published by the Free Software Foundation; with the 20Invariant Sections being ``Funding Free Software'', the Front-Cover 21Texts being (a) (see below), and with the Back-Cover Texts being (b) 22(see below). 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For example, a 62project's policy might require that all sources compile with 63<samp><span class="option">-Werror</span></samp> but certain files might have exceptions allowing 64specific types of warnings. Or, a project might selectively enable 65diagnostics and treat them as errors depending on which preprocessor 66macros are defined. 67 68 <dl> 69<dt><code>#pragma GCC diagnostic </code><var>kind</var> <var>option</var><dd><a name="index-pragma_002c-diagnostic-3235"></a> 70Modifies the disposition of a diagnostic. Note that not all 71diagnostics are modifiable; at the moment only warnings (normally 72controlled by ‘<samp><span class="samp">-W...</span></samp>’) can be controlled, and not all of them. 73Use <samp><span class="option">-fdiagnostics-show-option</span></samp> to determine which diagnostics 74are controllable and which option controls them. 75 76 <p><var>kind</var> is ‘<samp><span class="samp">error</span></samp>’ to treat this diagnostic as an error, 77‘<samp><span class="samp">warning</span></samp>’ to treat it like a warning (even if <samp><span class="option">-Werror</span></samp> is 78in effect), or ‘<samp><span class="samp">ignored</span></samp>’ if the diagnostic is to be ignored. 79<var>option</var> is a double quoted string which matches the command-line 80option. 81 82 <pre class="example"> #pragma GCC diagnostic warning "-Wformat" 83 #pragma GCC diagnostic error "-Wformat" 84 #pragma GCC diagnostic ignored "-Wformat" 85</pre> 86 <p>Note that these pragmas override any command-line options. GCC keeps 87track of the location of each pragma, and issues diagnostics according 88to the state as of that point in the source file. Thus, pragmas occurring 89after a line do not affect diagnostics caused by that line. 90 91 <br><dt><code>#pragma GCC diagnostic push</code><dt><code>#pragma GCC diagnostic pop</code><dd> 92Causes GCC to remember the state of the diagnostics as of each 93<code>push</code>, and restore to that point at each <code>pop</code>. If a 94<code>pop</code> has no matching <code>push</code>, the command line options are 95restored. 96 97 <pre class="example"> #pragma GCC diagnostic error "-Wuninitialized" 98 foo(a); /* error is given for this one */ 99 #pragma GCC diagnostic push 100 #pragma GCC diagnostic ignored "-Wuninitialized" 101 foo(b); /* no diagnostic for this one */ 102 #pragma GCC diagnostic pop 103 foo(c); /* error is given for this one */ 104 #pragma GCC diagnostic pop 105 foo(d); /* depends on command line options */ 106</pre> 107 </dl> 108 109 <p>GCC also offers a simple mechanism for printing messages during 110compilation. 111 112 <dl> 113<dt><code>#pragma message </code><var>string</var><dd><a name="index-pragma_002c-diagnostic-3236"></a> 114Prints <var>string</var> as a compiler message on compilation. The message 115is informational only, and is neither a compilation warning nor an error. 116 117 <pre class="smallexample"> #pragma message "Compiling " __FILE__ "..." 118</pre> 119 <p><var>string</var> may be parenthesized, and is printed with location 120information. For example, 121 122 <pre class="smallexample"> #define DO_PRAGMA(x) _Pragma (#x) 123 #define TODO(x) DO_PRAGMA(message ("TODO - " #x)) 124 125 TODO(Remember to fix this) 126</pre> 127 <p>prints ‘<samp><span class="samp">/tmp/file.c:4: note: #pragma message: 128TODO - Remember to fix this</span></samp>’. 129 130 </dl> 131 132 </body></html> 133 134