On Fri, Jun 07, 2024 at 12:12:19PM +0100, Ryan Roberts wrote: > On 04/06/2024 05:55, John Hubbard wrote: > > On 6/3/24 3:47 PM, Nathan Chancellor wrote: > >> Does CC=clang even work for the selftests? lib.mk here uses 'CC :=' so > >> won't CC=clang get overridden to CC=$(CROSS_COMPILE)gcc? > >> > > > > I received a report that someone (I forget who or what) was definitely > > attempting to just set CC=clang. But yes, it definitely doesn't work > > properly for CROSS_COMPILE. > > This history as I recall, is that I got a bug report [1] stating that: > > # tools/testing/selftests/fchmodat2$ make CC=clang > > and > > # tools/testing/selftests/openat2$ make CC=clang > > were both failing due to the -static-libsan / -static-libasan difference between > gcc and clang. I attempted to fix that with [2], which used cc-option to > determine which variant to use. That never got picked up, and John > coincidentally did a similar fix, but relying on LLVM=1 instead. > > If we are concluding that CC=clang is an invalid way to do this, then I guess we > should report that back to [1]? > > [1] https://lore.kernel.org/all/202404141807.LgsqXPY5-lkp@xxxxxxxxx/ > [2] > https://lore.kernel.org/linux-kselftest/20240417160740.2019530-1-ryan.roberts@xxxxxxx/ I can only speak from the perspective of the main kernel build, as I don't really know much if anything about the selftests, but I think CC=clang and LLVM=1 should both be valid. Ideally, they would behave as they do for the main kernel build (i.e., CC=clang just uses clang for the compiler and LLVM=1 uses the entire LLVM tools). I realize that for the selftests, there is probably little use for tools other than the compiler, assembler, and linker but I think consistency is desirable here. I am not at all familiar with the selftests build system, which is completely different from Kbuild, but I would ack a patch that does that. Otherwise, I think having a different meaning or handling of CC=clang or LLVM=1 is the end of the world, but I do think that it should be documented. Cheers, Nathan
