root6: use MacPorts llvm, if possible, and disable it completely on powerpc

[barracuda156]

Why does it need to build a bundled version of LLVM and why is it forced onto a user at all, given that it is not supported on some archs?

To a little surprise, build fails:

make[2]: Entering directory `/opt/local/var/macports/build/_opt_PPCSnowLeopardPorts_science_root6/root6/work/build'
[ 27%] Linking CXX executable ../../../../bin/clang-tblgen
cd /opt/local/var/macports/build/_opt_PPCSnowLeopardPorts_science_root6/root6/work/build/interpreter/llvm-project/llvm/tools/clang/utils/TableGen && /opt/local/bin/cmake -E cmake_link_script CMakeFiles/clang-tblgen.dir/link.txt --verbose=ON
/opt/local/bin/g++-mp-13 -pipe -Os -DNDEBUG -isystem/opt/local/include/LegacySupport -I/opt/local/include -D_GLIBCXX_USE_CXX11_ABI=0 -std=c++17 -Wno-implicit-fallthrough -Wno-noexcept-type -m32 -pipe -W -Wshadow -Wall -Woverloaded-virtual -fsigned-char -fno-common -pthread  -fPIC -fno-semantic-interposition -fvisibility-inlines-hidden -Werror=date-time -w -fno-common -Woverloaded-virtual -fno-strict-aliasing -O3 -DNDEBUG -arch ppc -mmacosx-version-min=10.6 -Wl,-search_paths_first -Wl,-headerpad_max_install_names -m64 -Wl,-headerpad_max_install_names -L/opt/local/lib -lMacportsLegacySupport -Wl,-rpath,/opt/local/lib/libgcc -mmacosx-version-min=10.6  -Wl,-dead_strip "CMakeFiles/obj.clang-tblgen.dir/ASTTableGen.cpp.o" "CMakeFiles/obj.clang-tblgen.dir/ClangASTNodesEmitter.cpp.o" "CMakeFiles/obj.clang-tblgen.dir/ClangASTPropertiesEmitter.cpp.o" "CMakeFiles/obj.clang-tblgen.dir/ClangAttrEmitter.cpp.o" "CMakeFiles/obj.clang-tblgen.dir/ClangCommentCommandInfoEmitter.cpp.o" "CMakeFiles/obj.clang-tblgen.dir/ClangCommentHTMLNamedCharacterReferenceEmitter.cpp.o" "CMakeFiles/obj.clang-tblgen.dir/ClangCommentHTMLTagsEmitter.cpp.o" "CMakeFiles/obj.clang-tblgen.dir/ClangDataCollectorsEmitter.cpp.o" "CMakeFiles/obj.clang-tblgen.dir/ClangDiagnosticsEmitter.cpp.o" "CMakeFiles/obj.clang-tblgen.dir/ClangOpcodesEmitter.cpp.o" "CMakeFiles/obj.clang-tblgen.dir/ClangOpenCLBuiltinEmitter.cpp.o" "CMakeFiles/obj.clang-tblgen.dir/ClangOptionDocEmitter.cpp.o" "CMakeFiles/obj.clang-tblgen.dir/ClangSACheckersEmitter.cpp.o" "CMakeFiles/obj.clang-tblgen.dir/ClangSyntaxEmitter.cpp.o" "CMakeFiles/obj.clang-tblgen.dir/ClangTypeNodesEmitter.cpp.o" "CMakeFiles/obj.clang-tblgen.dir/MveEmitter.cpp.o" "CMakeFiles/obj.clang-tblgen.dir/NeonEmitter.cpp.o" "CMakeFiles/obj.clang-tblgen.dir/RISCVVEmitter.cpp.o" "CMakeFiles/obj.clang-tblgen.dir/SveEmitter.cpp.o" "CMakeFiles/obj.clang-tblgen.dir/TableGen.cpp.o" -o ../../../../bin/clang-tblgen  ../../../../lib/libLLVMSupport.a ../../../../lib/libLLVMTableGen.a ../../../../lib/libLLVMSupport.a -lm /opt/local/lib/libz.dylib /opt/local/lib/libcurses.dylib ../../../../lib/libLLVMDemangle.a -lemutls_w
g++-mp-13: warning: '-m64' conflicts with '-arch ppc' ('-m64' ignored)
ld: could not find entry point "start" (perhaps missing crt1.o)
collect2: error: ld returned 1 exit status
make[2]: *** [interpreter/llvm-project/llvm/bin/clang-tblgen] Error 1

Errors suggest that the very setup is wrong also.

[cjones051073 (Chris Jones)]

ROOT chooses to build its own (modified) internal build of LLVM. There is no option to disable this and use a MacPorts build. If you want to discuss this further you need to do so with the upstream developers.

[barracuda156]

Replying to cjones051073:

ROOT chooses to build its own (modified) internal build of LLVM. There is no option to disable this and use a MacPorts build. If you want to discuss this further you need to do so with the upstream developers.

Thank you for responding. Fair enough, and this is not something I will pursue at the moment either.