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| <h4 class="subsection">6.54.10 Diagnostic Pragmas</h4> |
| |
| <p>GCC allows the user to selectively enable or disable certain types of |
| diagnostics, and change the kind of the diagnostic. For example, a |
| project's policy might require that all sources compile with |
| <samp><span class="option">-Werror</span></samp> but certain files might have exceptions allowing |
| specific types of warnings. Or, a project might selectively enable |
| diagnostics and treat them as errors depending on which preprocessor |
| macros are defined. |
| |
| <dl> |
| <dt><code>#pragma GCC diagnostic </code><var>kind</var> <var>option</var><dd><a name="index-pragma_002c-diagnostic-3140"></a> |
| Modifies the disposition of a diagnostic. Note that not all |
| diagnostics are modifiable; at the moment only warnings (normally |
| controlled by ‘<samp><span class="samp">-W...</span></samp>’) can be controlled, and not all of them. |
| Use <samp><span class="option">-fdiagnostics-show-option</span></samp> to determine which diagnostics |
| are controllable and which option controls them. |
| |
| <p><var>kind</var> is ‘<samp><span class="samp">error</span></samp>’ to treat this diagnostic as an error, |
| ‘<samp><span class="samp">warning</span></samp>’ to treat it like a warning (even if <samp><span class="option">-Werror</span></samp> is |
| in effect), or ‘<samp><span class="samp">ignored</span></samp>’ if the diagnostic is to be ignored. |
| <var>option</var> is a double quoted string which matches the command line |
| option. |
| |
| <pre class="example"> #pragma GCC diagnostic warning "-Wformat" |
| #pragma GCC diagnostic error "-Wformat" |
| #pragma GCC diagnostic ignored "-Wformat" |
| </pre> |
| <p>Note that these pragmas override any command line options. Also, |
| while it is syntactically valid to put these pragmas anywhere in your |
| sources, the only supported location for them is before any data or |
| functions are defined. Doing otherwise may result in unpredictable |
| results depending on how the optimizer manages your sources. If the |
| same option is listed multiple times, the last one specified is the |
| one that is in effect. This pragma is not intended to be a general |
| purpose replacement for command line options, but for implementing |
| strict control over project policies. |
| |
| </dl> |
| |
| <p>GCC also offers a simple mechanism for printing messages during |
| compilation. |
| |
| <dl> |
| <dt><code>#pragma message </code><var>string</var><dd><a name="index-pragma_002c-diagnostic-3141"></a> |
| Prints <var>string</var> as a compiler message on compilation. The message |
| is informational only, and is neither a compilation warning nor an error. |
| |
| <pre class="smallexample"> #pragma message "Compiling " __FILE__ "..." |
| </pre> |
| <p><var>string</var> may be parenthesized, and is printed with location |
| information. For example, |
| |
| <pre class="smallexample"> #define DO_PRAGMA(x) _Pragma (#x) |
| #define TODO(x) DO_PRAGMA(message ("TODO - " #x)) |
| |
| TODO(Remember to fix this) |
| </pre> |
| <p>prints ‘<samp><span class="samp">/tmp/file.c:4: note: #pragma message: |
| TODO - Remember to fix this</span></samp>’. |
| |
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