7af584ed87
If Clang is set up to link directly against libunwind (via the --unwindlib option, or the corresponding builtin default option), configuring libunwind will fail while bootstrapping (before the initial libunwind is built), because every cmake test will fail due to -lunwind not being found, and linking the shared library will fail similarly. Check if --unwindlib=none is supported, and add it in that case. Using check_c_compiler_flag on its own doesn't work, because that only adds the tested flag to the compilation command, and if -lunwind is missing, the linking step would still fail - instead try adding it to CMAKE_REQUIRED_FLAGS and restore the variable if it doesn't work. This avoids having to pass --unwindlib=none while building libunwind. Differential Revision: https://reviews.llvm.org/D112126
18 lines
688 B
CMake
18 lines
688 B
CMake
include(CMakePushCheckState)
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include(CheckCCompilerFlag)
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function(llvm_check_linker_flag flag dest)
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# If testing a flag with check_c_compiler_flag, it gets added to the compile
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# command only, but not to the linker command in that test. If the flag
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# is vital for linking to succeed, the test would fail even if it would
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# have succeeded if it was included on both commands.
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#
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# Therefore, try adding the flag to CMAKE_REQUIRED_FLAGS, which gets
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# added to both compiling and linking commands in the tests.
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cmake_push_check_state()
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set(CMAKE_REQUIRED_FLAGS "${CMAKE_REQUIRED_FLAGS} ${flag}")
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check_c_compiler_flag("" ${dest})
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cmake_pop_check_state()
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endfunction()
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