The change to C++17 for Emscripten was made in commit 37484dc. This update modified the CMake configuration to set CMAKE_CXX_STANDARD to 17 when the EMSCRIPTEN condition is true. However, despite these changes, the build failed to use C++17, leading to compilation errors.

The issue lies in the following:

    Top-level CMake configuration: The changed code sets the C++ standard based on the EMSCRIPTEN condition:
    CMake

    if(EMSCRIPTEN)
      set(CMAKE_CXX_STANDARD 17)
    else()
      set(CMAKE_CXX_STANDARD 11)
    endif()
    set(CMAKE_CXX_STANDARD_REQUIRED YES)

    This should ensure that Emscripten builds use at least C++17. However, in the build logs, Emscripten was not applying this configuration.

    Scoping problem: The CMAKE_CXX_STANDARD declaration applies globally but might be overridden elsewhere in project-specific or subdirectory CMakeLists.txt files. For example:
        The code in /bench, /exposed, or other directories may override or not inherit the correct C++ standard.
        These subdirectories may explicitly set target_compile_features or other settings conflicting with the top-level configuration.

    This can happen if subdirectory CMakeLists.txt files are missing explicit inheritance of the C++ standard set at the root level.

    Emscripten detection issue: If Emscripten's toolchain file isn't included early in the CMake configuration, the EMSCRIPTEN condition might not be evaluated correctly.

Fix Recommendations:

    Enforce C++17 globally for Emscripten: Use set_property to enforce the C++ standard for all targets, ensuring subdirectories inherit the configuration:
    CMake

    if(EMSCRIPTEN)
      set(CMAKE_CXX_STANDARD 17)
      set(CMAKE_CXX_STANDARD_REQUIRED YES)
      set_property(GLOBAL PROPERTY CXX_STANDARD 17)
    else()
      set(CMAKE_CXX_STANDARD 11)
    endif()

    Audit subdirectory configurations:
        Check subdirectory CMakeLists.txt files (like /bench/CMakeLists.txt) for target_compile_features or custom compiler flags. Ensure they do not conflict with the global configuration.

    Include the Emscripten toolchain file early: Make sure the Emscripten toolchain is loaded correctly so the EMSCRIPTEN condition is evaluated. If the condition is not recognized, add include(Platform/Emscripten) to ensure proper detection.

Let me know if you'd like assistance identifying conflicts in your subdirectory configuration files!

Code	File	Line	Column
set(CMAKE_CXX_STANDARD 17)	C:\PAR\Projects\Solvespace\git\extlib\mimalloc\test\CMakeLists.txt	5	11
  set(CMAKE_CXX_STANDARD 17)	C:\PAR\Projects\Solvespace\git\CMakeLists.txt	17	13
  set(CMAKE_CXX_STANDARD 11)	C:\PAR\Projects\Solvespace\git\CMakeLists.txt	19	13
set(CMAKE_CXX_STANDARD_REQUIRED YES)	C:\PAR\Projects\Solvespace\git\CMakeLists.txt	21	11
  set(CMAKE_CXX_STANDARD_COMPUTED_DEFAULT 98)	C:\PAR\Projects\Solvespace\git\cmake\Platform\Emscripten.cmake	152	13
set(CMAKE_CXX_STANDARD 11)	C:\PAR\Projects\Solvespace\git\extlib\angle\CMakeLists.txt	5	11
set(CMAKE_CXX_STANDARD_REQUIRED YES)	C:\PAR\Projects\Solvespace\git\extlib\angle\CMakeLists.txt	6	11
  set_property(TARGET btl_blaze PROPERTY CXX_STANDARD 14)	C:\PAR\Projects\Solvespace\git\extlib\eigen\bench\btl\libs\blaze\CMakeLists.txt	9	42
  get_target_property(targetCxxStandard ${SDK_BUILD_IR_TARGET} CXX_STANDARD)	C:\PAR\Projects\Solvespace\git\extlib\eigen\cmake\FindComputeCpp.cmake	251	64
set(CMAKE_CXX_STANDARD 17)	C:\PAR\Projects\Solvespace\git\extlib\eigen\cmake\FindTriSYCL.cmake	65	11
set(CXX_STANDARD_REQUIRED ON)	C:\PAR\Projects\Solvespace\git\extlib\eigen\cmake\FindTriSYCL.cmake	66	5
  set(CMAKE_CXX_STANDARD 11)	C:\PAR\Projects\Solvespace\git\extlib\eigen\CMakeLists.txt	80	13
  #set(CMAKE_CXX_STANDARD 03)	C:\PAR\Projects\Solvespace\git\extlib\eigen\CMakeLists.txt	86	14
  set(CMAKE_CXX_STANDARD 17)	C:\PAR\Projects\Solvespace\git\extlib\eigen\unsupported\doc\examples\SYCL\CMakeLists.txt	6	13
    set(CMAKE_CXX_STANDARD 14)	C:\PAR\Projects\Solvespace\git\extlib\eigen\unsupported\doc\examples\SYCL\CMakeLists.txt	11	15
    set(CMAKE_CXX_STANDARD 11)	C:\PAR\Projects\Solvespace\git\extlib\eigen\unsupported\doc\examples\SYCL\CMakeLists.txt	14	15
      set(CMAKE_CXX_STANDARD 17)	C:\PAR\Projects\Solvespace\git\extlib\eigen\unsupported\test\CMakeLists.txt	167	17
        set(CMAKE_CXX_STANDARD 14)	C:\PAR\Projects\Solvespace\git\extlib\eigen\unsupported\test\CMakeLists.txt	172	19
        set(CMAKE_CXX_STANDARD 11)	C:\PAR\Projects\Solvespace\git\extlib\eigen\unsupported\test\CMakeLists.txt	175	19
set(CMAKE_CXX_STANDARD 17)	C:\PAR\Projects\Solvespace\git\extlib\mimalloc\CMakeLists.txt	5	11