GCC_COLORS in combination with ccache

Question

I am using gcc 4.9.2 with ccache 3.1.10. My shell environment contains GCC_COLORS=auto (from here; tried yes and always too).

As a minimal test I compile this main.c file

int main() {
    int a;
    return 0;
}

with gcc -c main.c -Wall -o main.o and observe (as desired)

main.c: In function ‘main’:
main.c:2:7: warning: unused variable ‘a’ [-Wunused-variable]
   int a;
       ^

with main.c: and main.c:2:7:, ‘main’: and ‘a’ in bold face, the ^ in boldface green, and the warning: in magenta bold face.

Compiling with ccache the colorisation disappears.

NB: ccache gcc -Wall -c main.c -o main.o is colorless, but ccache gcc -Wall main.c -o main remains colored.

NB2: ccache gcc -Wall -c main.c -o main.o -fdiagnostics-color also preserves colors in the output.

Question: Is there a recommended way to have the export GCC_COLORS functionality with ccache? I'd prefer to have colors globally enabled (as through the ~/.MYSHELLrc) and without adding -fdiagnostics-color globally to $CFLAGS[0] and I want to avoid custom wrappers which parse the output messages (and might get confused with LC_MESSAGES settings).

[0]: I have many Makefiles which don't add their config to CFLAGS but overwrite the environment settings.

Answer 1

Not really sure it's relevant anymore, but I just tested with GCC_COLORS=yes with ccache version 3.4.1 and gcc 7.4.0 and that seems to work fine for me. I had the same issue when GCC_COLORS wasn't set.