Created attachment 924336 [details]
test code :
int *j = i;
in shell $g++ test.cxx
will have a diagnostics color output.
but $g++ -c test.cxx and $g++ -c -fdiagnostics-color=auto test.cxx
the output is black.
I just use $g++ -c -fdiagnostics-color=always test.cxx.
so -c and default diagnostics-color not compatible
when i remove ccache,the output have color.
Don't use ccache then, this is something beyond control of gcc.
ccache 3.2 (entering rawhide soon) seems to have this partially fixed, these give colorized output with it:
g++ -c -fdiagnostics-color=auto test.cxx
...but this still doesn't:
g++ -c test.cxx
Don't you need to set GCC_COLORS (or pass -fdiagnostics-color) to get color diagnostics from GCC in Fedora?
/ccache upstream maintainer, not running Fedora
Fedora has the same default as upstream trunk, i.e. even if GCC_COLORS env var is not defined, colors are output if stderr is a tty and TERM is not dumb.
I.e. as if trunk has been configured with the default --with-diagnostics-color=auto. Upstream 4.9 on the other side defaults to trunk's --with-diagnostics-color=auto-if-env. See https://gcc.gnu.org/gcc-5/changes.html for more details.
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From a ccache point of view, I don't see any good solution for this issue. The problem is that ccache needs to pass -fdiagnostics-color to the preprocessor to get colored output and that is currently done if GCC_COLORS is set. ccache can't just pass -fdiagnostics-color unconditionally since it doesn't know whether the compiler is new enough to support it.
Fedora 22 changed to end-of-life (EOL) status on 2016-07-19. Fedora 22 is
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