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[libc] Generate a stub for libpthread.a (#200908)

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Several build systems / existing scripts assume that pthread functions
are exposed through separate library (`libpthread.so` / `libpthread.a`)
and thus use `-lpthread` flag explicitly. Since llvm-libc puts all the
pthread functions into the regular `libc`, teach the CMake build rules
to produce an empty static archive `libpthread.a` for compatibility
purposes.
This commit is contained in:
Alexey Samsonov 2026-06-15 23:35:20 -07:00 committed by GitHub
parent ccef34d45a
commit f88e9de37a
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1 changed files with 25 additions and 0 deletions
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25
libc/lib/CMakeLists.txt
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@ -70,6 +70,29 @@ foreach(file ${added_bitcode_targets})
)
endforeach()
# Add empty archive libraries for compatibility with systems expecting certain
# bits of libc to be located in separate files (e.g. libpthread).
set(added_empty_archives "")
if(LLVM_LIBC_FULL_BUILD AND ${LIBC_TARGET_OS} STREQUAL "linux")
list(APPEND libc_empty_archive_names pthread)
foreach(archive ${libc_empty_archive_names})
set(empty_archive_path ${LIBC_LIBRARY_DIR}/lib${archive}.a)
add_custom_command(
OUTPUT ${empty_archive_path}
COMMAND ${CMAKE_AR} cqs ${empty_archive_path}
COMMENT "Creating empty archive ${empty_archive_path}"
VERBATIM
)
install(
FILES ${empty_archive_path}
DESTINATION ${LIBC_INSTALL_LIBRARY_DIR}
COMPONENT libc
)
add_custom_target(empty-${archive} ALL DEPENDS ${empty_archive_path})
list(APPEND added_empty_archives empty-${archive})
endforeach()
endif()
set(startup_target "")
if(LLVM_LIBC_FULL_BUILD AND NOT LIBC_TARGET_OS_IS_BAREMETAL)
# For now we will disable libc-startup installation for baremetal. The
@ -86,6 +109,7 @@ endif()
add_custom_target(install-libc
DEPENDS ${added_archive_targets}
${added_bitcode_targets}
${added_empty_archives}
${startup_target}
${header_install_target}
COMMAND "${CMAKE_COMMAND}"
@ -94,6 +118,7 @@ add_custom_target(install-libc
add_custom_target(install-libc-stripped
DEPENDS ${added_archive_targets}
${added_bitcode_targets}
${added_empty_archives}
${startup_target}
${header_install_target}
COMMAND "${CMAKE_COMMAND}"