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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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16 changes: 5 additions & 11 deletions llvm/cmake/modules/AddLLVM.cmake
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Original file line number Diff line number Diff line change
Expand Up @@ -51,19 +51,13 @@ 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 "")
# TODO: GTEST_HAS_RTTI should be determined automatically, evaluate whether
# the explicit definition is actually required.
list(APPEND LLVM_COMPILE_DEFINITIONS GTEST_HAS_RTTI=0)
if (LLVM_COMPILER_IS_GCC_COMPATIBLE)
list(APPEND LLVM_COMPILE_CXXFLAGS "-fno-rtti")
elseif (MSVC)
list(APPEND LLVM_COMPILE_CXXFLAGS "/GR-")
elseif (CMAKE_CXX_COMPILER_ID MATCHES "XL")
list(APPEND LLVM_COMPILE_CXXFLAGS "-qnortti")
endif ()
elseif(MSVC)
list(APPEND LLVM_COMPILE_CXXFLAGS "/GR")
list(APPEND LLVM_COMPILE_CXXFLAGS ${LLVM_CXXFLAGS_RTTI_DISABLE})
else()
list(APPEND LLVM_COMPILE_CXXFLAGS ${LLVM_CXXFLAGS_RTTI_ENABLE})
endif()

target_compile_options(${name} PRIVATE ${LLVM_COMPILE_FLAGS} $<$<COMPILE_LANGUAGE:CXX>:${LLVM_COMPILE_CXXFLAGS}>)
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15 changes: 12 additions & 3 deletions llvm/cmake/modules/HandleLLVMOptions.cmake
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Expand Up @@ -1162,13 +1162,22 @@ elseif(MSVC)
endif()
endif()

if(MSVC)
# llvm_update_compile_flags adds one of these to each target.
set(LLVM_CXXFLAGS_RTTI_DISABLE "")
set(LLVM_CXXFLAGS_RTTI_ENABLE "")
if(LLVM_COMPILER_IS_GCC_COMPATIBLE)
set(LLVM_CXXFLAGS_RTTI_DISABLE "-fno-rtti")
elseif(MSVC)
# Remove flags here, for exceptions and RTTI.
# Each target property or source property should be responsible to control
# them.
# CL.EXE complains to override flags like "/GR /GR-".
string(REGEX REPLACE "(^| ) */EH[-cs]+ *( |$)" "\\1 \\2" CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS}")
string(REGEX REPLACE "(^| ) */GR-? *( |$)" "\\1 \\2" CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS}")
string(REGEX REPLACE "(^| ) */EH[-cs]+ *( |$)" "\\1 \\2" CMAKE_CXXFLAGS "${CMAKE_CXX_FLAGS}")
string(REGEX REPLACE "(^| ) */GR-? *( |$)" "\\1 \\2" CMAKE_CXXFLAGS "${CMAKE_CXX_FLAGS}")
set(LLVM_CXXFLAGS_RTTI_DISABLE "/GR-")
set(LLVM_CXXFLAGS_RTTI_ENABLE "/GR")
elseif(CMAKE_CXXCOMPILER_ID MATCHES "XL")
set(LLVM_CXXFLAGS_RTTI_DISABLE "-qnortti")
endif()

# Provide public options to globally control RTTI and EH
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12 changes: 7 additions & 5 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 @@ -61,9 +58,14 @@ 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} ${LLVM_DEFINITIONS}")
if(LLVM_ENABLE_RTTI)
append(${LLVM_CXXFLAGS_RTTI_ENABLE} LLVM_CXXFLAGS)
else()
append(${LLVM_CXXFLAGS_RTTI_DISABLE} LLVM_CXXFLAGS)
endif()
set(LLVM_BUILD_SYSTEM cmake)
set(LLVM_HAS_RTTI ${LLVM_CONFIG_HAS_RTTI})
set(LLVM_HAS_RTTI ${LLVM_ENABLE_RTTI})
set(LLVM_DYLIB_VERSION "${LLVM_VERSION_MAJOR}${LLVM_VERSION_SUFFIX}")
set(LLVM_SHARED_LIBRARY_PREFIX "${CMAKE_SHARED_LIBRARY_PREFIX}")

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