Error when using installed c++ module with MSVC

[autoantwort]

First of all I am not sure if this is a cmake or fmtlib issue:
I am using the latest MSVC Version and CMake 4.0.3
I am configured master fmtlib with -G Ninja -DFMT_MODULE=ON and installed it to prefix

If I try to use this in my project via import fmt; and find_package(fmt CONFIG REQUIRED) + target_link_libraries(test-lib PRIVATE fmt::fmt) I get the following error:

[build] [1/7  14% :: 0.405] Scanning F:\git_projects\fmt\build\dist\include\fmt\src\fmt.cc for CXX dependencies
[build] FAILED: CMakeFiles/fmt__fmt@synth_c5f2e4a688d1.dir/4feac3a26265.bmi.ddi 
[build] C:\PROGRA~1\MIB055~1\2022\PROFES~1\VC\Tools\MSVC\1444~1.352\bin\Hostx64\x64\cl.exe  -external:IF:\git_projects\fmt\build\dist\include -external:W0 /DWIN32 /D_WINDOWS /EHsc /Ob0 /Od -std:c++20 -MDd -RTC1 -Zi /interface /ifcOutput CMakeFiles\fmt.dir\fmt.ifc /utf-8 /reference fmt=CMakeFiles\fmt.dir\fmt.ifc -ifcOnly -ifcOutput CMakeFiles\fmt__fmt@synth_c5f2e4a688d1.dir\4feac3a26265.bmi F:\git_projects\fmt\build\dist\include\fmt\src\fmt.cc -nologo -TP -showIncludes -scanDependencies CMakeFiles\fmt__fmt@synth_c5f2e4a688d1.dir\4feac3a26265.bmi.ddi -FoCMakeFiles\fmt__fmt@synth_c5f2e4a688d1.dir\4feac3a26265.bmi
[build] c1xx: error C3472: new output file name CMakeFiles\fmt__fmt@synth_c5f2e4a688d1.dir\4feac3a26265.bmi (set on command line) conflicts with previous file name CMakeFiles\fmt.dir\fmt.ifc

The problem seems to be the following:

dist/lib/cmake/fmt/fmt-targets.cmake

set_target_properties(fmt::fmt PROPERTIES
  CXX_MODULE_STD ""
  IMPORTED_CXX_MODULES_COMPILE_FEATURES "cxx_std_20;cxx_std_11"
  IMPORTED_CXX_MODULES_COMPILE_OPTIONS "/interface;/ifcOutput;CMakeFiles\\fmt.dir\\fmt.ifc;\$<\$<AND:\$<COMPILE_LANGUAGE:CXX>,\$<CXX_COMPILER_ID:MSVC>>:/utf-8>"
  IMPORTED_CXX_MODULES_INCLUDE_DIRECTORIES "${_IMPORT_PREFIX}/include"
  INTERFACE_COMPILE_FEATURES "cxx_std_20;cxx_std_11"
  INTERFACE_COMPILE_OPTIONS "/reference;fmt=CMakeFiles\\fmt.dir\\fmt.ifc;\$<\$<AND:\$<COMPILE_LANGUAGE:CXX>,\$<CXX_COMPILER_ID:MSVC>>:/utf-8>"
  INTERFACE_INCLUDE_DIRECTORIES "${_IMPORT_PREFIX}/include"
)

If I remove /interface;/ifcOutput;CMakeFiles\\fmt.dir\\fmt.ifc and /reference;fmt=CMakeFiles\\fmt.dir\\fmt.ifc the project compiles fine. The question is who is adding these options?

[vitaut]

@DanielaE do you by any chance know what might be causing this?

[autoantwort]

I tried again with cmake 4.1.0-rc1 and cmake master, but cmake simply crashes at the end ... Will report a bug there (Issue is https://gitlab.kitware.com/cmake/cmake/-/issues/27054, was fixed in https://gitlab.kitware.com/cmake/cmake/-/merge_requests/10938)

[autoantwort]

Ah it comes from here:

fmt/CMakeLists.txt

Lines 28 to 43 in 20c8fda

	function(enable_module target)
	if (MSVC)
	if(CMAKE_GENERATOR STREQUAL "Ninja")
	# Ninja dyndep expects the .ifc output to be located in a specific relative path
	file(RELATIVE_PATH BMI_DIR "${CMAKE_BINARY_DIR}" "${CMAKE_CURRENT_BINARY_DIR}/CMakeFiles/${target}.dir")
	else()
	set(BMI_DIR "${CMAKE_CURRENT_BINARY_DIR}")
	endif()
	file(TO_NATIVE_PATH "${BMI_DIR}/${target}.ifc" BMI)
	target_compile_options(${target}
	PRIVATE /interface /ifcOutput ${BMI}
	INTERFACE /reference fmt=${BMI})
	set_target_properties(${target} PROPERTIES ADDITIONAL_CLEAN_FILES ${BMI})
	set_source_files_properties(${BMI} PROPERTIES GENERATED ON)
	endif ()
	endfunction()

[autoantwort]

If I simply remove the whole code there is works with msvc and ninja/msbuild and with install/add_submodule