On 6/7/24 10:15 AM, Nathan Chancellor wrote:
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:
...
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.
OK, that can be easily done, as shown below. And there are so far only
a handful of selftests that key off of LLVM (plus a few of my pending
patches). I can post this, plus a few patches (and patch updates for
pending patches) to use the new CC_IS_CLANG where appropriate:
diff --git a/tools/testing/selftests/lib.mk b/tools/testing/selftests/lib.mk
index 429535816dbd..ea643d1a65dc 100644
--- a/tools/testing/selftests/lib.mk
+++ b/tools/testing/selftests/lib.mk
@@ -43,6 +43,15 @@ else
CC := $(CROSS_COMPILE)gcc
endif # LLVM
+# CC might have been set above (by inferring it from LLVM==1), or CC might have
+# been set from the environment. In either case, if CC is an invocation of clang
+# in any form, set CC_IS_CLANG. This allows subsystem selftests to selectively
+# control clang-specific behavior, such as, in particular, compiler warnings.
+CC_IS_CLANG := 0
+ifeq ($(findstring clang,$(CC)),clang)
+ CC_IS_CLANG := 1
+endif
+
ifeq (0,$(MAKELEVEL))
ifeq ($(OUTPUT),)
OUTPUT := $(shell pwd)
thanks,
--
John Hubbard
NVIDIA
