[PATCH] D19895: cmake: Introduce TEST_SUITE_C_FLAGS, TEST_SUITE_CXX_FLAGS, etc.

[Justin Bogner via llvm-commits]

Matthias Braun via llvm-commits <llvm-commits at lists.llvm.org> writes:
> MatzeB created this revision.
> MatzeB added reviewers: cmatthews, kristof.beyls, jmolloy.
> MatzeB added a subscriber: llvm-commits.
> MatzeB set the repository for this revision to rL LLVM.
> Herald added a subscriber: mcrosier.
>
> Intuitively one would use CMAKE_C_FLAGS, CMAKE_CXX_FLAGS and
> CMAKE_EXE_LINKER_FLAGS to inject custom flags into the build. However
> this clashes with the use of cmake cache files which want to add flags as well.
> A user specifying CMAKE_C_FLAGS would (accidentally) override the
> flags set by the cache files.

AFAIK The usual trick is to set CMAKE_C_FLAGS_RELEASE or
CMAKE_C_FLAGS_MINSIZEREL or whatever in the cache file, and leave the
CMAKE_C_FLAGS for the command line user to do what they want with.

> The solution here is to introduce a new set of flags called
> TEST_SUITE_C_FLAGS, TEST_SUITE_CXX_FLAGS and TEST_SUITE_EXE_LINKER_FLAGS
> as a means for users to specify additional flags. This way the flags
> will not override the settings from the cache file.
>
> In order to educate users to use the new flags a warning message is
> displayed if CMAKE_C_FLAGS is set.
>
> Repository:
>   rL LLVM
>
> http://reviews.llvm.org/D19895
>
> Files:
>   CMakeLists.txt
>   cmake/caches/util/arch_flags.cmake
>
> Index: cmake/caches/util/arch_flags.cmake
> ===================================================================
> --- cmake/caches/util/arch_flags.cmake
> +++ cmake/caches/util/arch_flags.cmake
> @@ -2,3 +2,5 @@
>  set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} ${ARCH_FLAGS}" CACHE STRING "")
>  set(CMAKE_MODULE_LINKER_FLAGS "${CMAKE_MODULE_LINKER_FLAGS} ${ARCH_FLAGS}" CACHE STRING "")
>  set(CMAKE_EXE_LINKER_FLAGS "${CMAKE_EXE_LINKER_FLAGS} ${ARCH_FLAGS}" CACHE STRING "")
> +# Silence the warning in the toplevel CMakeLists.txt.
> +set(EXPECTED_CMAKE_C_FLAGS "${CMAKE_C_FLAGS}" CACHE STRING "")
> Index: CMakeLists.txt
> ===================================================================
> --- CMakeLists.txt
> +++ CMakeLists.txt
> @@ -12,13 +12,33 @@
>  mark_as_advanced(CMAKE_INSTALL_PREFIX)
>  # On the other hand we often want to switch compiler or cflags
>  mark_as_advanced(CLEAR CMAKE_C_COMPILER CMAKE_CXX_COMPILER CMAKE_LINKER
> -  CMAKE_C_FLAGS CMAKE_C_FLAGS_DEBUG CMAKE_C_FLAGS_MINSIZEREL
> +  CMAKE_C_FLAGS_DEBUG CMAKE_C_FLAGS_MINSIZEREL
>    CMAKE_C_FLAGS_RELEASE CMAKE_C_FLAGS_RELWITHDEBINFO
> -  CMAKE_CXX_FLAGS CMAKE_CXX_FLAGS_DEBUG CMAKE_CXX_FLAGS_MINSIZEREL
> +  CMAKE_CXX_FLAGS_DEBUG CMAKE_CXX_FLAGS_MINSIZEREL
>    CMAKE_CXX_FLAGS_RELEASE CMAKE_CXX_FLAGS_RELWITHDEBINFO
> -  CMAKE_EXE_LINKER_FLAGS CMAKE_EXE_LINKER_FLAGS_DEBUG
> -  CMAKE_EXE_LINKER_FLAGS_MINSIZEREL CMAKE_EXE_LINKER_FLAGS_RELEASE
> -  CMAKE_EXE_LINKER_FLAGS_RELWITHDEBINFO)
> +  CMAKE_EXE_LINKER_FLAGS_DEBUG CMAKE_EXE_LINKER_FLAGS_MINSIZEREL
> +  CMAKE_EXE_LINKER_FLAGS_RELEASE CMAKE_EXE_LINKER_FLAGS_RELWITHDEBINFO)
> +
> +# Encourage people to use TEST_SUITE_C_FLAGS/TEST_SUITE_CXX_FLAGS so
> +# CMAKE_C_FLAGS can be used exclusively by -C cachefiles for specifying
> +# target flags without the user accidentally overriding them.
> +set(EXPECTED_CMAKE_C_FLAGS "" CACHE STRING
> +    "Allows cache files to disable the CMAKE_C_FLAGS warning message")
> +mark_as_advanced(EXPECTED_CMAKE_C_FLAGS)
> +if(NOT "${CMAKE_C_FLAGS}" STREQUAL "${EXPECTED_CMAKE_C_FLAGS}")
> +  message(WARNING "
> +Specifying CMAKE_C_FLAGS, CMAKE_CXX_FLAGS, \
> +CMAKE_EXE_LINKER_FLAGS is discouraged. Use TEST_SUITE_C_FLAGS, \
> +TEST_SUITE_CXX_FLAGS and TEST_SUITE_EXE_LINKER_FLAGS instead.\
> +")
> +endif()
> +mark_as_advanced(CMAKE_C_FLAGS CMAKE_CXX_FLAGS CMAKE_EXE_LINKER_FLAGS)
> +set(TEST_SUITE_C_FLAGS "" CACHE STRING "Flags used by the C compiler.")
> +set(TEST_SUITE_CXX_FLAGS "${TEST_SUITE_C_FLAGS}" CACHE STRING "Flags used by the C++ compiler.")
> +set(TEST_SUITE_EXE_LINKER_FLAGS "" CACHE STRING "Flags used by the linker.")
> +set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} ${TEST_SUITE_C_FLAGS}")
> +set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} ${TEST_SUITE_CXX_FLAGS}")
> +set(CMAKE_EXE_LINKER_FLAGS "${CMAKE_EXE_LINKER_FLAGS} ${TEST_SUITE_EXE_LINKER_FLAGS}")
>  
>  project(test-suite C CXX)
>  
>
>