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[CMake] Re-add -fno-rtti to llvm-config --cxxflags #174084

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Merged
aengelke merged 3 commits into from
Jan 1, 2026
Merged

[CMake] Re-add -fno-rtti to llvm-config --cxxflags #174084

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dd55b7d
[CMake] Re-add -fno-rtti to llvm-config --cxxflags
aengelke Dec 31, 2025
f8864b7
different, less hacky approach
aengelke Jan 1, 2026
20e8ba7
remove debug print
aengelke Jan 1, 2026
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19 changes: 13 additions & 6 deletions llvm/cmake/modules/AddLLVM.cmake
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Original file line number Diff line number Diff line change
Expand Up @@ -51,20 +51,27 @@ function(llvm_update_compile_flags name)

# LLVM_REQUIRES_RTTI is an internal flag that individual
# targets can use to force RTTI
set(LLVM_CONFIG_HAS_RTTI YES CACHE INTERNAL "")
if(NOT (LLVM_REQUIRES_RTTI OR LLVM_ENABLE_RTTI))
set(LLVM_CONFIG_HAS_RTTI NO CACHE INTERNAL "")
list(APPEND LLVM_COMPILE_DEFINITIONS GTEST_HAS_RTTI=0)
if (LLVM_COMPILER_IS_GCC_COMPATIBLE)
list(APPEND LLVM_COMPILE_CXXFLAGS "-fno-rtti")
set(LLVM_CONFIG_RTTI_CXXFLAG "-fno-rtti" CACHE INTERNAL "")
elseif (MSVC)
list(APPEND LLVM_COMPILE_CXXFLAGS "/GR-")
set(LLVM_CONFIG_RTTI_CXXFLAG "/GR-" CACHE INTERNAL "")
elseif (CMAKE_CXX_COMPILER_ID MATCHES "XL")
list(APPEND LLVM_COMPILE_CXXFLAGS "-qnortti")
set(LLVM_CONFIG_RTTI_CXXFLAG "-qnortti" CACHE INTERNAL "")
else()
set(LLVM_CONFIG_RTTI_CXXFLAG "" CACHE INTERNAL "")
endif ()
elseif(MSVC)
list(APPEND LLVM_COMPILE_CXXFLAGS "/GR")
else()
set(LLVM_CONFIG_HAS_RTTI YES CACHE INTERNAL "")
if(MSVC)
set(LLVM_CONFIG_RTTI_CXXFLAG "/GR" CACHE INTERNAL "")
else()
set(LLVM_CONFIG_RTTI_CXXFLAG "" CACHE INTERNAL "")
endif()
endif()
list(APPEND LLVM_COMPILE_CXXFLAGS ${LLVM_CONFIG_RTTI_CXXFLAG})

target_compile_options(${name} PRIVATE ${LLVM_COMPILE_FLAGS} $<$<COMPILE_LANGUAGE:CXX>:${LLVM_COMPILE_CXXFLAGS}>)
target_compile_definitions(${name} PRIVATE ${LLVM_COMPILE_DEFINITIONS})
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5 changes: 1 addition & 4 deletions llvm/tools/llvm-config/CMakeLists.txt
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Expand Up @@ -45,9 +45,6 @@ endforeach()

string(REPLACE ";" " " SYSTEM_LIBS "${SYSTEM_LIBS}")

# Fetch target specific compile options, e.g. RTTI option
get_property(COMPILE_FLAGS TARGET llvm-config PROPERTY COMPILE_FLAGS)

# NOTE: We don't want to start extracting any random C/CXX flags that the
# user may add that could affect the ABI. We only want to extract flags
# that have been added by the LLVM build system.
Expand All @@ -61,7 +58,7 @@ set(LLVM_CPPFLAGS "${LLVM_DEFINITIONS}")
set(LLVM_CFLAGS "${LLVM_C_STD_FLAG} ${LLVM_DEFINITIONS}")
# The language standard potentially affects the ABI/API of LLVM, so we want
# to make sure it is reported by llvm-config.
set(LLVM_CXXFLAGS "${CMAKE_CXX${CMAKE_CXX_STANDARD}_STANDARD_COMPILE_OPTION} ${LLVM_CXX_STDLIB_FLAG} ${COMPILE_FLAGS} ${LLVM_DEFINITIONS}")
set(LLVM_CXXFLAGS "${CMAKE_CXX${CMAKE_CXX_STANDARD}_STANDARD_COMPILE_OPTION} ${LLVM_CXX_STDLIB_FLAG} ${LLVM_CONFIG_RTTI_CXXFLAG} ${LLVM_DEFINITIONS}")
set(LLVM_BUILD_SYSTEM cmake)
set(LLVM_HAS_RTTI ${LLVM_CONFIG_HAS_RTTI})
set(LLVM_DYLIB_VERSION "${LLVM_VERSION_MAJOR}${LLVM_VERSION_SUFFIX}")
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