Summary

The current recipe for metis allows conflicting optimization levels to appear on the compile line in a way that isn't expected. For example: spack -d install metis build_type=RelWithDebInfo cflags="-O3 -g" doesn't compile with the expected CFLAGS. I expect to see compile lines similar to this:

/usr/bin/gcc -O3 -g <include directives and defines> -o file.o -c file.c

Actual Result

/usr/bin/gcc -O3 -g <include directives and defines> -O3 -O2 -g -DDNDEBUG -o file.o -c file.c

Because -O2 is listed after -O3 the optimization is not what I expect. I believe the -O2 -g -DDNDEBUG flags are inserted by CMake as they are the default CMAKE_C__FLAGS_RELWITHDEBINFO values for gcc.

I'm actually not sure where that second -O3 is coming from.

Possible solution

If SPACK_CFLAGS is set in the build environment, then zero-out the cmake defaulted CMAKE_C_FLAGS_XXX variables.

I have a patch incoming (#6840) to fix this problem (if it passes review).

Related Issues

#6732
#6640
#6749
#6745
#6714