Remove -Werror from default flags or give cmake option to avoid it

[wjwwood]

Does the feature exist in the most recent commit?

No, the -Werror flag is included by default on master as of now:

googletest/googletest/cmake/internal_utils.cmake

Lines 86 to 93 in 7153098

	elseif (CMAKE_CXX_COMPILER_ID STREQUAL "Clang")
	set(cxx_base_flags "-Wall -Wshadow -Werror -Wconversion")
	set(cxx_exception_flags "-fexceptions")
	set(cxx_no_exception_flags "-fno-exceptions")
	set(cxx_strict_flags "-W -Wpointer-arith -Wreturn-type -Wcast-qual -Wwrite-strings -Wswitch -Wunused-parameter -Wcast-align -Wchar-subscripts -Winline -Wredundant-decls")
	set(cxx_no_rtti_flags "-fno-rtti")
	elseif (CMAKE_COMPILER_IS_GNUCXX)
	set(cxx_base_flags "-Wall -Wshadow -Werror")

Why do we need this feature?

When building googletest/googlemock as part of another project (recommended best practice AFAIK), if that project is built with extremely pedantic warning flags, e.g. clang's -Weverything, then googletest will fail with errors rather than warnings. It is desirable for the project to finish building so all warning can be collected. googletest failing part way through due to -Werror prevents this.

Describe the proposal

In my opinion, googletest should not set -Werror in its cmake logic. The user (developer on local machine, CI infrastructure, CD infrastructure) can enable this with export CXXFLAGS=-Werror (and export CFLAGS=-Werror if needed) or with an argument to cmake -DCMAKE_CXX_FLAGS=-Werror. The opposite is not true, however (AFAIK), because though you can disable individual warnings as errors with -Wno-error=..., there is no -werror or -Wno-error=all or something like that. If there is, then that would probably be a sufficient workaround, and I'd appreciate anyone who could point out how to do that to me.

However, if there is no desire to change existing infrastructure, then I'd request a way to influence googletest to not include this flag, likely by having a cmake build option like GOOGLE_TEST_INCLUDE_W_ERROR and have it default to true. This would allow a project to prevent google test from adding that flag when using ExternalProject_Add, for example.

Without either removing the flag altogether, or a build option to prevent it, the only alternative I can think of is patching googletest before compiling, again you could do this with ExternalProject_Add, but that is fragile when upgrading to newer versions of googletest, and therefore a burden to maintain.

Is the feature specific to an operating system, compiler, or build system version?

It was added in 1ded831.

It is specific to CMake, and it appears to be specific to clang and gcc:

• clang:

  googletest/googletest/cmake/internal_utils.cmake

  Lines 86 to 87 in 7153098

  	elseif (CMAKE_CXX_COMPILER_ID STREQUAL "Clang")
  	set(cxx_base_flags "-Wall -Wshadow -Werror -Wconversion")

• gcc:

  googletest/googletest/cmake/internal_utils.cmake

  Lines 92 to 93 in 7153098

  	elseif (CMAKE_COMPILER_IS_GNUCXX)
  	set(cxx_base_flags "-Wall -Wshadow -Werror")

[derekmauro]

Thanks for pointing this out. I completely agree and will get it removed.