Compilation flags are unexpected

[steve-downey]

[5/12] /usr/bin/g++  -I/home/sdowney/src/bemanproject/exemplar/main/src/beman/exemplar/../../../include -O3  -O2 -g -DNDEBUG -std=gnu++20 -MD -MT examples/CMakeFiles/beman.exemplar.examples.identity_as_default_projection.dir/identity_as_default_projection.cpp.o -MF examples/CMakeFiles/beman.exemplar.examples.identity_as_default_projection.dir/identity_as_default_projection.cpp.o.d -o examples/CMakeFiles/beman.exemplar.examples.identity_as_default_projection.dir/identity_as_default_projection.cpp.o -c /home/sdowney/src/bemanproject/exemplar/main/examples/identity_as_default_projection.cpp

Note the repeated optimization levels

I think this may be due to using the _INIT forms of the FLAGS variables?
Docs:

CMake may prepend or append content to the value based on the environment and target platform.

[wusatosi]

Expanded log:

[5/12] /usr/bin/g++ -I/home/sdowney/src/bemanproject/exemplar/main/src/beman/exemplar/../../../include
-O3 -O2 -g -DNDEBUG -std=gnu++20 -MD -MT
examples/CMakeFiles/beman.exemplar.examples.identity_as_default_projection.dir/identity_as_default_projection.cpp.o -MF examples/CMakeFiles/beman.exemplar.examples.identity_as_default_projection.dir/identity_as_default_projection.cpp.o.d -o examples/CMakeFiles/beman.exemplar.examples.identity_as_default_projection.dir/identity_as_default_projection.cpp.o -c /home/sdowney/src/bemanproject/exemplar/main/examples/identity_as_default_projection.cpp

Hum.... I can investigate this.

Thanks for checking this!!!

[wusatosi]

Executing workflow step 1 of 3: configure preset "gcc-release"

Preset CMake variables:

CMAKE_BUILD_TYPE="RelWithDebInfo"
CMAKE_CXX_STANDARD="20"
CMAKE_EXPORT_COMPILE_COMMANDS="ON"
CMAKE_PROJECT_TOP_LEVEL_INCLUDES="./cmake/use-fetch-content.cmake"
CMAKE_TOOLCHAIN_FILE="cmake/gnu-toolchain.cmake"

TOOLCHAIN: CMAKE_CXX_FLAGS_RELWITHDEBINFO_INIT -O3
TOOLCHAIN: CMAKE_CXX_FLAGS_RELEASE_INIT -O3

The toolchain file is not putting both -O3 and -O2 there.

[wusatosi]

Confirm replacing CMAKE_CXX_FLAGS_RELWITHDEBINFO_INIT with CMAKE_CXX_FLAGS_RELWITHDEBINFO fixes this.

Should we fix issue by just using non init variables? or is there alternative ways to approach this?

[steve-downey]

This may be a case of cmake "helping" when we actually know better, for example setting -g3 rather than just -g. It may be specified for a particular compiler which "wins" but I certainly don't remember, and first and last are both reasonable.

[wermos]

It may be specified for a particular compiler which "wins"

For GCC, the last one wins.

As per the docs:

If you use multiple -g options, with or without level numbers, the last such option is the one that is effective.