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| <h3 class="section">3.7 Options to Control Diagnostic Messages Formatting</h3> |
| |
| <p><a name="index-options-to-control-diagnostics-formatting-212"></a><a name="index-diagnostic-messages-213"></a><a name="index-message-formatting-214"></a> |
| Traditionally, diagnostic messages have been formatted irrespective of |
| the output device's aspect (e.g. its width, <small class="dots">...</small>). The options described |
| below can be used to control the diagnostic messages formatting |
| algorithm, e.g. how many characters per line, how often source location |
| information should be reported. Right now, only the C++ front end can |
| honor these options. However it is expected, in the near future, that |
| the remaining front ends would be able to digest them correctly. |
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| <dl> |
| <dt><code>-fmessage-length=</code><var>n</var><dd><a name="index-fmessage_002dlength-215"></a>Try to format error messages so that they fit on lines of about <var>n</var> |
| characters. The default is 72 characters for <samp><span class="command">g++</span></samp> and 0 for the rest of |
| the front ends supported by GCC. If <var>n</var> is zero, then no |
| line-wrapping will be done; each error message will appear on a single |
| line. |
| |
| <p><a name="index-fdiagnostics_002dshow_002dlocation-216"></a><br><dt><code>-fdiagnostics-show-location=once</code><dd>Only meaningful in line-wrapping mode. Instructs the diagnostic messages |
| reporter to emit <em>once</em> source location information; that is, in |
| case the message is too long to fit on a single physical line and has to |
| be wrapped, the source location won't be emitted (as prefix) again, |
| over and over, in subsequent continuation lines. This is the default |
| behavior. |
| |
| <br><dt><code>-fdiagnostics-show-location=every-line</code><dd>Only meaningful in line-wrapping mode. Instructs the diagnostic |
| messages reporter to emit the same source location information (as |
| prefix) for physical lines that result from the process of breaking |
| a message which is too long to fit on a single line. |
| |
| <br><dt><code>-fdiagnostics-show-option</code><dd><a name="index-fdiagnostics_002dshow_002doption-217"></a>This option instructs the diagnostic machinery to add text to each |
| diagnostic emitted, which indicates which command line option directly |
| controls that diagnostic, when such an option is known to the |
| diagnostic machinery. |
| |
| <br><dt><code>-Wcoverage-mismatch</code><dd><a name="index-Wcoverage_002dmismatch-218"></a>Warn if feedback profiles do not match when using the |
| <samp><span class="option">-fprofile-use</span></samp> option. |
| If a source file was changed between <samp><span class="option">-fprofile-gen</span></samp> and |
| <samp><span class="option">-fprofile-use</span></samp>, the files with the profile feedback can fail |
| to match the source file and GCC can not use the profile feedback |
| information. By default, GCC emits an error message in this case. |
| The option <samp><span class="option">-Wcoverage-mismatch</span></samp> emits a warning instead of an |
| error. GCC does not use appropriate feedback profiles, so using this |
| option can result in poorly optimized code. This option is useful |
| only in the case of very minor changes such as bug fixes to an |
| existing code-base. |
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