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Fix lantern compilation with clang compilers #280

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Fix lantern compilation with clang compilers #280

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5d28dd5
Fix lantern compilation with clang compilers
Ngalstyan4 Feb 4, 2024
cc0e532
is linking libstdc++.a still needed?
Ngalstyan4 Feb 4, 2024
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40 changes: 8 additions & 32 deletions CMakeLists.txt
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Original file line number Diff line number Diff line change
Expand Up @@ -174,41 +174,17 @@ set_target_properties(

# THIRD PARTY LIBRARIES

# needed to make sure cmake does not add libstdc++ to the linker command when an
# external cpp library is added more at`
# link in c++ runtime so our extension can be binary-distributed to environments with no libstdc++
# N.B. the flag is meaningful for clang++ and g++, but not to clang and gcc, so we need to make sure CXX is set
# as the linker language
target_link_options(lantern PRIVATE -static-libstdc++)
# interesting discussion on all the hoops one has to go through to statically link stdc++ when
# using C as the link language. We used to do that, but it seems there is no reason to
# https://cmake-developers.cmake.narkive.com/JnbrDyGT/setting-linker-language-still-adds-lstdc
if(NOT APPLE)
# clang handles static libstdc++ differently than gcc
if ("${CMAKE_CXX_COMPILER_ID}" STREQUAL "Clang")
find_library(STATIC_LIBSTDCPP NAMES libstdc++.a PATHS ${CMAKE_CXX_IMPLICIT_LINK_DIRECTORIES})

if(STATIC_LIBSTDCPP)
set(CMAKE_CXX_IMPLICIT_LINK_LIBRARIES "${CMAKE_CXX_IMPLICIT_LINK_LIBRARIES};${STATIC_LIBSTDCPP}")
endif()
else()
# apples does not understand -static-libstdc++ used in usearch to bundle libstdc++ with the
# created archive.
# so, on apple we dynamically link to the c++ runtime
# todo:: find a way to statically link the c++ runtime on mac
set(CMAKE_CXX_IMPLICIT_LINK_LIBRARIES "")
set(CMAKE_CXX_IMPLICIT_LINK_DIRECTORIES "")
endif()
endif()

# Note: -static-libstdc++ is only meaningful for dynamic builds.
# If we ever switch back to statically linking usearch or other third party libs,
# we need to explicitly link against libstdc++.a
if (CMAKE_CXX_COMPILER_ID STREQUAL "GNU")
target_link_options(lantern PRIVATE -static-libstdc++)
elseif (CMAKE_CXX_COMPILER_ID MATCHES "Clang")
target_link_options(lantern PRIVATE -static)
endif ()
# not sure why, but the above is not enough to force pulling cpp runtime into lantern.so
# the following is also necessary
set_target_properties(lantern PROPERTIES LINKER_LANGUAGE CXX)
# todo:: why is still needed?
target_link_libraries(lantern PRIVATE "libstdc++.a")

set_target_properties(lantern PROPERTIES LINKER_LANGUAGE C)

target_compile_definitions(lantern PRIVATE LANTERN_USE_USEARCH)
target_compile_definitions(lantern PRIVATE "USEARCH_USE_SIMSIMD=$<BOOL:${USEARCH_USE_SIMSIMD}>")

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