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[CMake] do not let builtin_clang search again for LLVM if builtin_llvm=OFF #23371

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Merged
guitargeek merged 2 commits into from
Sep 16, 2026
Merged

[CMake] do not let builtin_clang search again for LLVM if builtin_llvm=OFF #23371

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[interpreter] do not let builtin_clang search again for LLVM if built…
ferdymercury Sep 15, 2026
80875d8
[cmake] better variable name and commenting
ferdymercury Sep 16, 2026
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17 changes: 16 additions & 1 deletion interpreter/CMakeLists.txt
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Original file line number Diff line number Diff line change
Expand Up @@ -393,14 +393,29 @@ else()

# Disable linking against shared LLVM
set(LLVM_LINK_LLVM_DYLIB OFF)
# To ensure this override stays constant, we need to avoid subdirectories calling find_package(LLVM),
# which would set it to ON again if system was compiled that way
# Define a macro with a toggle flag to override find_package, that will only be visible in this scope, not in parent one.
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# TEMPORARY: remove this workaround once ROOT can link against the shared
# libLLVM.so for builtin_llvm=OFF
macro(find_package _package_name)
if(ROOT_SKIP_FIND_LLVM_WITHIN_CLANG AND "${_package_name}" STREQUAL "LLVM")
message(STATUS "[ROOT] Suppressed find_package(LLVM) at ${CMAKE_CURRENT_LIST_FILE}:${CMAKE_CURRENT_LIST_LINE}"
" to keep LLVM_LINK_LLVM_DYLIB=OFF.")
else()
_find_package(${_package_name} ${ARGN})
endif()
endmacro()

# Always build LLVM with C++17. It is not necessary to compile with the same
# C++ standard as the rest of ROOT and sometimes it doesn't even work.
set(_cxx_standard ${CMAKE_CXX_STANDARD})
set(CMAKE_CXX_STANDARD 17)

set(ROOT_SKIP_FIND_LLVM_WITHIN_CLANG ON)
add_subdirectory(llvm-project/clang EXCLUDE_FROM_ALL)

set(ROOT_SKIP_FIND_LLVM_WITHIN_CLANG OFF)

set(CMAKE_CXX_STANDARD ${_cxx_standard})
endif(builtin_clang)

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