CMake GoogleTest override flags

January 13, 2026

GoogleTest internally set CMake compiler flags are too aggressive for end users, and can cause build errors. We experienced this with Intel oneAPI, and created a workaround for the GoogleTest-consuming CMake project to override the offending flags. This technique is useful in general with third-party CMake projects, including those obtained by FetchContent.

For GoogleTest, we determined that Intel oneAPI was experiencing nusiance internal errors:

Windows “-WX” flag
Linux “-Werror” flag

We overrode those flags with this CMake script:

FetchContent_MakeAvailable(googletest)

if(CMAKE_CXX_COMPILER_ID STREQUAL "IntelLLVM")
  foreach(t IN ITEMS gtest gtest_main gmock gmock_main)
    if(WIN32)
      # necessary since GoogleTest injects /WX blindly and that fails builds with modern IntelLLVM.
      # https://learn.microsoft.com/en-us/cpp/build/reference/compiler-option-warning-level
      target_compile_options(${t} PRIVATE $<$<COMPILE_LANGUAGE:CXX>:/WX->)
    else()
      # necessary to avoid
      # error: unknown warning option '-Wno-implicit-float-size-conversion' [-Werror,-Wunknown-warning-option]
      target_compile_options(${t} PRIVATE $<$<COMPILE_LANGUAGE:CXX>:-Wno-error=unknown-warning-option>)
    endif()
  endforeach()
endif()

The override “/WX-” nullifies the /WX flag that errors for nuisance warnings internal to GoogleTest. The “-Wno-” flag is the same as the underlying GCC compiler on Linux.