3.7 Options to Control Diagnostic Messages Formatting
Traditionally, diagnostic messages have been formatted irrespective of
the output device's aspect (e.g. its width, ...). 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.
- Try to format error messages so that they fit on lines of about n
characters. The default is 72 characters for g++ and 0 for the rest of
the front ends supported by GCC. If n is zero, then no
line-wrapping will be done; each error message will appear on a single
- Only meaningful in line-wrapping mode. Instructs the diagnostic messages
reporter to emit once 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
- 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.
- By default, each diagnostic emitted includes text which indicates the
command line option that directly controls the diagnostic (if such an
option is known to the diagnostic machinery). Specifying the
-fno-diagnostics-show-option flag suppresses that behavior.
- Warn if feedback profiles do not match when using the
If a source file was changed between -fprofile-gen and
-fprofile-use, the files with the profile feedback can fail
to match the source file and GCC can not use the profile feedback
information. By default, this warning is enabled and is treated as an
error. -Wno-coverage-mismatch can be used to disable the
warning or -Wno-error=coverage-mismatch can be used to
disable the error. Disable the error for this warning can result in
poorly optimized code, so disabling the error is useful only in the
case of very minor changes such as bug fixes to an existing code-base.
Completely disabling the warning is not recommended.