Since LLVM 18 support C++ 23, I tried to enable it in 6.34.00-rc1.
I have done the following things:
set -DCMAKE_CXX_STANDARD=23 when building ROOT.
Patch source file of ROOT (around line 164 of file cmake/modules/CheckCompiler.cmake, sorry I could not post hyperlink as a new user), to make it successfully configured.
Finally I get a working ROOT. root-config --cflags print:
It seems this variable is only useful when using ROOT with CMake (not when building root), and this variable is actually used to set default CMAKE_CXX_STANDARD. But I am using the interpreter of ROOT.
I managed to make it works, with some additional fix.
Should I split the pr into two, one for Cling repository at GitHub, and another for ROOT repository at GitHub, or just submit a single pr to ROOT repository?