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[6.42] [CMake] Only report include dirs known to cling as compiler defaults #24023

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Merged
guitargeek merged 1 commit into from
Nov 6, 2026
+40 −1
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[6.42] [CMake] Only report include dirs known to cling as compiler defaults #24023

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41 changes: 40 additions & 1 deletion cmake/modules/RootMacros.cmake
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Original file line number Diff line number Diff line change
Expand Up @@ -754,9 +754,48 @@ function(ROOT_GENERATE_DICTIONARY dictionary)
endforeach()
endif()

# rootcling does not promote compiler default include directories to -I,
# assuming that cling adds them by itself. Cling, however, only adds the C++
# standard library directories, its own builtin headers and the sysroot
# directories added by the clang driver. Directories injected by compiler
# wrappers or environment variables like CPATH are unknown to cling at
# runtime, so only report the former as compiler defaults.
if(CMAKE_SYSROOT)
set(sysroot "${CMAKE_SYSROOT}")
elseif(APPLE AND _CMAKE_OSX_SYSROOT_PATH)
# The SDK path that CMake resolves from CMAKE_OSX_SYSROOT (possibly empty
# or a bare SDK name) and passes to the compiler as -isysroot.
set(sysroot "${_CMAKE_OSX_SYSROOT_PATH}")
elseif(APPLE AND IS_DIRECTORY "${CMAKE_OSX_SYSROOT}")
set(sysroot "${CMAKE_OSX_SYSROOT}")
else()
set(sysroot "")
endif()
# Normalize like the implicit include directories (no trailing slash).
if(sysroot)
get_filename_component(sysroot "${sysroot}" ABSOLUTE)
string(REGEX REPLACE "/+$" "" sysroot "${sysroot}")
endif()
# What the clang driver adds, see AddClangSystemIncludeArgs() in
# clang/lib/Driver/ToolChains/{Linux,Darwin}.cpp. The multiarch directory
# <sysroot>/usr/include/<triple> is matched below. C library directories that
# the builtin clang is configured with (C_INCLUDE_DIRS, colon-separated) are
# reported in addition: a C library directory must never be promoted to -I.
set(sysrootIncDirs "${sysroot}/usr/local/include" "${sysroot}/include" "${sysroot}/usr/include")
set(clingCIncDirs)
if(C_INCLUDE_DIRS AND NOT WIN32)
string(REPLACE ":" ";" clingCIncDirs "${C_INCLUDE_DIRS}")
list(TRANSFORM clingCIncDirs REPLACE "/+$" "")
endif()
set(compIncPaths)
foreach(implinc IN LISTS CMAKE_CXX_IMPLICIT_INCLUDE_DIRECTORIES CMAKE_C_IMPLICIT_INCLUDE_DIRECTORIES)
list(APPEND compIncPaths "-compilerI${implinc}")
get_filename_component(implincParent "${implinc}" DIRECTORY)
get_filename_component(implincName "${implinc}" NAME)
if(implinc MATCHES "/c\\+\\+(/|$)" OR implinc MATCHES "/lib(64)?/(gcc|clang)/"
OR implinc IN_LIST sysrootIncDirs OR implinc IN_LIST clingCIncDirs
OR (implincParent STREQUAL "${sysroot}/usr/include" AND implincName MATCHES "^[^-]+-[^-]+-[^-]+"))
list(APPEND compIncPaths "-compilerI${implinc}")
endif()
endforeach()

# Keep the byproducts (rdict pcm, rootmap, C++ module) newer than the
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