forked from OSchip/llvm-project
[libc++] Simplify how we define the linker script for libc++
Trying to be generic didn't work properly because we had to special-case some interface libraries that we didn't want in the linker script. Instead, only look at the ABI and the unwinding libraries explicitly. This should solve the issue reported by @dim in [1]. [1]: https://discourse.llvm.org/t/15-0-0-rc1-has-been-tagged/64174/22 Differential Revision: https://reviews.llvm.org/D131037
This commit is contained in:
Louis Dionne
parent
44b4f4df31
commit
b7fb856397
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@ -1,56 +0,0 @@
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# This function defines a linker script in place of the symlink traditionally
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# created for shared libraries.
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#
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# More specifically, this function goes through the PUBLIC and INTERFACE
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# library dependencies of <target> and gathers them into a linker script,
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# such that those libraries are linked against when the shared library for
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# <target> is linked against.
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#
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# Arguments:
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# <target>: A target representing a shared library. A linker script will be
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# created in place of that target's TARGET_LINKER_FILE, which is
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# the symlink pointing to the actual shared library (usually
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# libFoo.so pointing to libFoo.so.1, which itself points to
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# libFoo.so.1.0).
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function(define_linker_script target)
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if (NOT TARGET "${target}")
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message(FATAL_ERROR "The provided target '${target}' is not actually a target.")
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endif()
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get_target_property(target_type "${target}" TYPE)
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if (NOT "${target_type}" STREQUAL "SHARED_LIBRARY")
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message(FATAL_ERROR "The provided target '${target}' is not a shared library (its type is '${target_type}').")
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endif()
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set(symlink "$<TARGET_LINKER_FILE:${target}>")
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set(soname "$<TARGET_SONAME_FILE_NAME:${target}>")
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get_target_property(interface_libs "${target}" INTERFACE_LINK_LIBRARIES)
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set(link_libraries)
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if (interface_libs)
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foreach(lib IN LISTS interface_libs)
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if ("${lib}" MATCHES "cxx-headers|ParallelSTL")
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continue()
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endif()
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# If ${lib} is not a target, we use a dummy target which we know will
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# have an OUTPUT_NAME property so that CMake doesn't fail when evaluating
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# the non-selected branch of the `IF`. It doesn't matter what it evaluates
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# to because it's not selected, but it must not cause an error.
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# See https://gitlab.kitware.com/cmake/cmake/-/issues/21045.
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set(output_name_tgt "$<IF:$<TARGET_EXISTS:${lib}>,${lib},${target}>")
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set(libname "$<IF:$<TARGET_EXISTS:${lib}>,$<TARGET_PROPERTY:${output_name_tgt},OUTPUT_NAME>,${lib}>")
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list(APPEND link_libraries "${CMAKE_LINK_LIBRARY_FLAG}${libname}")
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endforeach()
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endif()
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string(REPLACE ";" " " link_libraries "${link_libraries}")
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set(linker_script "INPUT(${soname} ${link_libraries})")
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add_custom_command(TARGET "${target}" POST_BUILD
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COMMAND "${CMAKE_COMMAND}" -E remove "${symlink}"
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COMMAND "${CMAKE_COMMAND}" -E echo "${linker_script}" > "${symlink}"
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COMMENT "Generating linker script: '${linker_script}' as file ${symlink}"
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VERBATIM
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)
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endfunction()
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@ -212,20 +212,6 @@ if (LIBCXX_ENABLE_SHARED)
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cxx_add_common_build_flags(cxx_shared)
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cxx_set_common_defines(cxx_shared)
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# Link against LLVM libunwind
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# Note that we do need to link against libunwind directly to ensure that the correct
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# dependencies are recorded when creating a linker script.
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# TODO: Look into modifying the linker script creation to recursively consider interface libraries
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if (LIBCXXABI_USE_LLVM_UNWINDER)
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if (LIBCXXABI_STATICALLY_LINK_UNWINDER_IN_SHARED_LIBRARY)
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# libunwind is already included in libc++abi
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elseif (TARGET unwind_shared OR HAVE_LIBUNWIND)
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target_link_libraries(cxx_shared PUBLIC unwind_shared)
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else()
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target_link_libraries(cxx_shared PUBLIC unwind)
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endif()
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endif()
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# Link against libc++abi
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if (LIBCXX_STATICALLY_LINK_ABI_IN_SHARED_LIBRARY)
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target_link_libraries(cxx_shared PRIVATE libcxx-abi-shared-objects)
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@ -254,8 +240,30 @@ if (LIBCXX_ENABLE_SHARED)
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# Generate a linker script in place of a libc++.so symlink.
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if (LIBCXX_ENABLE_ABI_LINKER_SCRIPT)
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include(DefineLinkerScript)
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define_linker_script(cxx_shared)
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set(link_libraries)
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set(imported_libname "$<TARGET_PROPERTY:libcxx-abi-shared,IMPORTED_LIBNAME>")
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set(output_name "$<TARGET_PROPERTY:libcxx-abi-shared,OUTPUT_NAME>")
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string(APPEND link_libraries "${CMAKE_LINK_LIBRARY_FLAG}$<IF:$<BOOL:${imported_libname}>,${imported_libname},${output_name}>")
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# TODO: Move to the same approach as above for the unwind library
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if (LIBCXXABI_USE_LLVM_UNWINDER)
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if (LIBCXXABI_STATICALLY_LINK_UNWINDER_IN_SHARED_LIBRARY)
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# libunwind is already included in libc++abi
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elseif (TARGET unwind_shared OR HAVE_LIBUNWIND)
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string(APPEND link_libraries " ${CMAKE_LINK_LIBRARY_FLAG}$<TARGET_PROPERTY:unwind_shared,OUTPUT_NAME>")
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else()
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string(APPEND link_libraries " ${CMAKE_LINK_LIBRARY_FLAG}unwind")
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endif()
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endif()
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set(linker_script "INPUT($<TARGET_SONAME_FILE_NAME:cxx_shared> ${link_libraries})")
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add_custom_command(TARGET cxx_shared POST_BUILD
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COMMAND "${CMAKE_COMMAND}" -E remove "$<TARGET_LINKER_FILE:cxx_shared>"
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COMMAND "${CMAKE_COMMAND}" -E echo "${linker_script}" > "$<TARGET_LINKER_FILE:cxx_shared>"
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COMMENT "Generating linker script: '${linker_script}' as file $<TARGET_LINKER_FILE:cxx_shared>"
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VERBATIM
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)
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endif()
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list(APPEND LIBCXX_BUILD_TARGETS "cxx_shared")
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