Failed to build on Clang/Windows: `W4` and `WX` flags passed to Clang

[LesleyLai]

Hi, thanks for this amazing library! I've used it a long throughout the years.

I am trying to build approval tests with Clang on Windows, and I got the following error:

clang++: error: no such file or directory: '/W4'
clang++: error: no such file or directory: '/WX'

It appears that those warning flags are being added by CMake/WarningsAsErrors.cmake.

My current escape hatch:

get_target_property(approval_tests_opts ApprovalTests COMPILE_OPTIONS)

if (approval_tests_opts)
    string(REPLACE "/W4" "" approval_tests_opts "${approval_tests_opts}")
    string(REPLACE "/WX" "" approval_tests_opts "${approval_tests_opts}")
    set_target_properties(ApprovalTests PROPERTIES COMPILE_OPTIONS "${approval_tests_opts}")
endif ()

Extra information of my build

Project: Charlie3D
target to build: charlie3d_test

The Approval Test libary are pulled via CPM:

CPMAddPackage(
        NAME approvaltests
        GITHUB_REPOSITORY approvals/ApprovalTests.cpp
        GIT_TAG v.10.13.0
        SYSTEM TRUE
)

CMake generated command:

C:\Users\Lenovo\AppData\Local\Programs\CLion\bin\cmake\win\x64\bin\cmake.exe -DCMAKE_BUILD_TYPE=Debug -DCMAKE_MAKE_PROGRAM=C:/Users/Lenovo/AppData/Local/Programs/CLion/bin/ninja/win/x64/ninja.exe -DBEYOND_CORE_BUILD_TESTS=ON -DCMAKE_TOOLCHAIN_FILE=C:\Users\Lenovo\.clion-vcpkg\vcpkg\scripts\buildsystems\vcpkg.cmake -DCHARLIE3D_BUILD_TESTS=OFF -G Ninja -S E:\Dev\Charlie3D -B E:\Dev\Charlie3D\cmake-build-debug-clang

Other Information:

clang version 21.1.8
Target: x86_64-pc-windows-msvc
cmake version 3.31.6 (CMake; JetBrains IDE bundle; build 29)
OS: Windows 11