incompatible BUILD_SHARED_LIBS + WINDOWS_EXPORT_ALL_SYMBOLS + INTERPROCEDURAL_OPTIMIZATION #334
Comments
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I have a workaround. For any DLL that will export functions/classes, the If LTCG isn't put on the linker flags, then when dependencies compiled GL+LTCG are linked without it, then the linker will run for seconds->minutes and then notice a dependency is GL+LTCG and discard the link in process and restart the link with LTCG. The linker will literally display that warning and the restart on console output. The depthai-core project has three libraries which are affected: # disable /GL and enable /LTCG for bug https://github.com/luxonis/depthai-core/issues/334
if(WIN32 AND MSVC AND CMAKE_WINDOWS_EXPORT_ALL_SYMBOLS)
get_target_property(_INTER_OPT ${TARGET_CORE_NAME} INTERPROCEDURAL_OPTIMIZATION)
if(_INTER_OPT)
message(STATUS "Workaround MSVC dll exports with INTERPROCEDURAL_OPTIMIZATION")
set_target_properties(${TARGET_CORE_NAME} PROPERTIES INTERPROCEDURAL_OPTIMIZATION OFF)
target_link_options(${TARGET_CORE_NAME} PRIVATE /LTCG)
endif()
unset(_INTER_OPT)
endif()Using that approach, I am able to enable INTERPROCEDURAL_OPTIMIZATION for Windows shared lib (DLL) builds. Is this something the depthai-core project wants to include? If yes, I can make a PR. |
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Thanks for reporting and for the proposed workaround. Unfortunate that this is required... I think it could fit - can you try performing this snippet by looping through |
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Sure. I will explore that looping, macro/func, and/or separate include file in The cmake code that does this is https://github.com/Kitware/CMake/blob/master/Source/bindexplib.cxx. After reviewing it and then reading https://docs.microsoft.com/en-us/cpp/build/reference/gl-whole-program-optimization?view=msvc-170 and https://docs.microsoft.com/en-us/cpp/build/reference/symbols?view=msvc-170
This setting combination may be impossible to WINDOWS_EXPORT_ALL_SYMBOLS scan for symbols since even MSVC's own tool dumpbin can not do it. |
The interprocedular (
Thanks. |
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I think When the MSVC linker runs and links in obj files it looks for the I set the The subset of devs that encounter this are those with the combination: Windows, MSVC, global opt, cmake, building a DLL from code that needs WINDOWS_EXPORT_ALL_SYMBOLS. It is that last qualifier that depthai-core catches this limitation. Other projects use a macro and declspec to declare which APIs will be available (exported) outside the DLL. e.g. Overall, this is a minor annoy and I don't see any urgent need for depthai-core to stop using |
- workaround MSVC incompat BUILD_SHARED_LIBS + WINDOWS_EXPORT_ALL_SYMBOLS + INTERPROCEDURAL_OPTIMIZATION - fixes luxonis#334
- workaround MSVC incompat BUILD_SHARED_LIBS + WINDOWS_EXPORT_ALL_SYMBOLS + INTERPROCEDURAL_OPTIMIZATION - fixes luxonis#334
On Windows, all Release builds fail when
BUILD_SHARED_LIBS=ONandCMAKE_INTERPROCEDURAL_OPTIMIZATION=ON.I think because CMakeLists.txt line 15 sets
CMAKE_WINDOWS_EXPORT_ALL_SYMBOLS=ON.And that
...EXPORT_ALL_SYMBOLS=ONfeature of cmake is incompatible withCMAKE_INTERPROCEDURAL_OPTIMIZATION=ON.When both are
ONandBUILD_SHARED_LIBS=ONthen theexports.def filecreated by theCMAKE_WINDOWS_EXPORT_ALL_SYMBOLSfeature is empty. With no def file, nothing is exported from the DLL and the linker fails.Because depthai-core uses
CMAKE_WINDOWS_EXPORT_ALL_SYMBOLSinstead of exporting via Windows standard approachs (e.g __declspec), it appears (from what I know so far) that theINTERPROCEDURAL_OPTIMIZATION=ONsetting can not be used on Windows with the MSVC toolchain. FYI,INTERPROCEDURAL_OPTIMIZATION=ONcmake setting enables link-time code generation on MSVC with/LTCG.Setup
develop3d5dc2eRepro
BUILD_SHARED_LIBS=ON,CMAKE_INTERPROCEDURAL_OPTIMIZATION=ON, andDEPTHAI_ENABLE_BACKWARD=ONResult
The file
depthai-core\build\CMakeFiles\depthai-core.dir\exports.defis 0 bytes.If I change
CMAKE_INTERPROCEDURAL_OPTIMIZATION=OFFand do the same repro steps then the build is successful and theexports.deffile is 5+MB.Expected
Clean build, no errors.
Workarounds
CMAKE_INTERPROCEDURAL_OPTIMIZATION=OFForINTERPROCEDURAL_OPTIMIZATION=OFF. This is the default.Related
https://vcpkg.readthedocs.io/en/latest/maintainers/maintainer-guide/#do-not-add-cmake_windows_export_all_symbols
https://gitlab.kitware.com/cmake/cmake/-/issues/23035
https://manpages.debian.org/bullseye-backports/cmake-data/cmake-properties.7.en.html#WINDOWS_EXPORT_ALL_SYMBOLS
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