Pass CFLAGS and CPPFLAGS to build process

[coldtobi]

When overriding compiler options in cmake CMake does not by default honor environment set compiler options, this has to be manually considered. In Debian, CFLAGS and CPPFLAGS are injected by the environment to set some archive-wide defaults, for example enabling hardening features.

(If the environment variables are not set, this patch has no effect.)

Patch origin:
https://salsa.debian.org/games-team/minetest/-/blob/master/debian/patches/enable_hardening.patch (minus some extra blank lines, which I missed when creating the patch for Debian))

[numberZero]

Does any CMake-based project does that?

[numberZero]

Actually, this PR made me realize there is a problem. See #164 for details.

[coldtobi]

Does any CMake-based project does that?

This is a known issue with CMake. Background: https://gitlab.kitware.com/cmake/cmake/-/issues/20631 https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=653916

[numberZero]

Can’t you simply cmake -DCMAKE_C_FLAGS="$CFLAGS $CPPFLAGS" -DCMAKE_CXX_FLAGS="$CXXFLAGS $CPPFLAGS"?

[Desour]

CFLAGS and CXXFLAGS are already used to initialize CMAKE_CXX_FLAGS and CMAKE_C_FLAGS (see https://cmake.org/cmake/help/latest/envvar/CXXFLAGS.html, https://cmake.org/cmake/help/latest/envvar/CFLAGS.html).
We should probably use those cmake variables, and also add the preprocessor flags (CPPFLAGS).

[numberZero]

CFLAGS and CXXFLAGS are already used to initialize CMAKE_CXX_FLAGS and CMAKE_C_FLAGS (see https://cmake.org/cmake/help/latest/envvar/CXXFLAGS.html, https://cmake.org/cmake/help/latest/envvar/CFLAGS.html).

They are, but not CPPFLAGS. And specifying CMAKE_CXX_FLAGS explicitly on the command line overrides CXXFLAGS IIRC.

We should probably use those cmake variables

No, CMake does that itself.

and also add the preprocessor flags (CPPFLAGS).

If you really want to use that, add a cache variable (e.g. CPP_FLAGS), initialize it to CPPFLAGS, and add to compilation flags of everything (either via add_compile_options or non-cache CMAKE_CXX_FLAGS). Going without a dedicated cache variable would lead to very fragile builds.

[numberZero]

Fragile. Each time CMake runs, it rereads these environment variables.

[Desour]

https://irc.minetest.net/minetest-dev/2023-05-14#i_6083236

[okias]

minetest/minetest#12799 (comment)