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[flang-rt] Use --as-needed for linking flang-rt libraries. (#130856)

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This change makes sure that there is no unnecessary library
dependencies like libc++/libstdc++.
This commit is contained in:
Slava Zakharin 2025-03-14 08:26:03 -07:00 committed by GitHub
parent fdb4b89bc0
commit eeb27331dc
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2 changed files with 20 additions and 0 deletions
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6
flang-rt/CMakeLists.txt
View File

@ -244,6 +244,12 @@ check_cxx_compiler_flag("-UTESTFLAG" FLANG_RT_SUPPORTS_UNDEFINE_FLAG)
# Check whether -fno-lto is supported.
check_cxx_compiler_flag(-fno-lto FLANG_RT_HAS_FNO_LTO_FLAG)
# Check whether -Wl,--as-needed is supported.
check_linker_flag(C "LINKER:--as-needed" LINKER_SUPPORTS_AS_NEEDED)
if (LINKER_SUPPORTS_AS_NEEDED)
set(LINKER_AS_NEEDED_OPT "LINKER:--as-needed")
endif()
# Different platform may have different name for the POSIX thread library.
# For example, libpthread.a on AIX. Search for it as it is needed when
# building the shared flang_rt.runtime.so.

14
flang-rt/cmake/modules/AddFlangRT.cmake
View File

@ -145,6 +145,20 @@ function (add_flangrt_library name)
if (Threads_FOUND)
target_link_libraries(${name_shared} PUBLIC Threads::Threads)
endif ()
# Special dependencies handling for shared libraries only:
#
# flang-rt libraries must not depend on libc++/libstdc++,
# so set the linker language to C to avoid the unnecessary
# library dependence. Note that libc++/libstdc++ may still
# come through CMAKE_CXX_IMPLICIT_LINK_LIBRARIES.
set_target_properties(${name_shared} PROPERTIES LINKER_LANGUAGE C)
# Use --as-needed to avoid unnecessary dependencies.
if (LINKER_AS_NEEDED_OPT)
target_link_options(${name_shared} BEFORE PRIVATE
"${LINKER_AS_NEEDED_OPT}"
)
endif()
endif ()
if (libtargets)