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Message-ID: <20240704182332.GB300903@thelio-3990X> Date: Thu, 4 Jul 2024 11:23:32 -0700 From: Nathan Chancellor <nathan@...nel.org> To: John Hubbard <jhubbard@...dia.com> Cc: Shuah Khan <shuah@...nel.org>, Nick Desaulniers <ndesaulniers@...gle.com>, Bill Wendling <morbo@...gle.com>, Ryan Roberts <ryan.roberts@....com>, Justin Stitt <justinstitt@...gle.com>, Muhammad Usama Anjum <usama.anjum@...labora.com>, linux-kselftest@...r.kernel.org, llvm@...ts.linux.dev, LKML <linux-kernel@...r.kernel.org> Subject: Re: [RFC PATCH] selftests: introduce and use SELFTESTS_CC_IS_CLANG instead of LLVM On Wed, Jul 03, 2024 at 08:04:52PM -0700, John Hubbard wrote: > Current practice in the selftests Makefiles is to use $(LLVM) as a way > to decide if clang is being used as the compiler (and/or the linker > front end). Unfortunately, this does not cover all of the use cases: > > 1) CC could have been set within selftests/lib.mk, by inferring it from > LLVM==1, or > > 2) CC could have been set externally, such as when cross compiling. > > Solution: In order to allow subsystem selftests to more accurately > control clang-specific behavior, such as compiler options, provide a new > Makefile variable: SELFTESTS_CC_IS_CLANG. If $(CC) contains an > invocation of clang in any form, then SELFTESTS_CC_IS_CLANG will be > non-empty. > > SELFTESTS_CC_IS_CLANG does not specify which linker is being used. > However, it can still help with linker options, because $(CC) is often > used to do both the compile and link steps (often in the same step). > > Signed-off-by: John Hubbard <jhubbard@...dia.com> > --- > > Hi, > > If this looks reasonable, I'll break it up into separate patches and > post it as a non-RFC. Aside from the polarity issue with the checks as you already noted, this seems reasonable to me and matches what I had in mind. > tools/testing/selftests/bpf/Makefile | 2 +- > tools/testing/selftests/fchmodat2/Makefile | 12 +++++++----- > tools/testing/selftests/hid/Makefile | 2 +- > tools/testing/selftests/lib.mk | 15 +++++++++++++++ > tools/testing/selftests/openat2/Makefile | 16 +++++++++------- > 5 files changed, 33 insertions(+), 14 deletions(-) > > diff --git a/tools/testing/selftests/bpf/Makefile b/tools/testing/selftests/bpf/Makefile > index dd49c1d23a60..6b924297ab71 100644 > --- a/tools/testing/selftests/bpf/Makefile > +++ b/tools/testing/selftests/bpf/Makefile > @@ -55,7 +55,7 @@ progs/test_sk_lookup.c-CFLAGS := -fno-strict-aliasing > progs/timer_crash.c-CFLAGS := -fno-strict-aliasing > progs/test_global_func9.c-CFLAGS := -fno-strict-aliasing > > -ifneq ($(LLVM),) > +ifeq ($(SELFTESTS_CC_IS_CLANG),) > # Silence some warnings when compiled with clang > CFLAGS += -Wno-unused-command-line-argument > endif > diff --git a/tools/testing/selftests/fchmodat2/Makefile b/tools/testing/selftests/fchmodat2/Makefile > index 4373cea79b79..d00b01be5d96 100644 > --- a/tools/testing/selftests/fchmodat2/Makefile > +++ b/tools/testing/selftests/fchmodat2/Makefile > @@ -2,14 +2,16 @@ > > CFLAGS += -Wall -O2 -g -fsanitize=address -fsanitize=undefined $(KHDR_INCLUDES) > > +TEST_GEN_PROGS := fchmodat2_test > + > +include ../lib.mk > + > # gcc requires -static-libasan in order to ensure that Address Sanitizer's > # library is the first one loaded. However, clang already statically links the > # Address Sanitizer if -fsanitize is specified. Therefore, simply omit > # -static-libasan for clang builds. > -ifeq ($(LLVM),) > +# This check must be done after including ../lib.mk, in order to pick up the > +# correct value of SELFTESTS_CC_IS_CLANG. > +ifeq ($(SELFTESTS_CC_IS_CLANG),) > CFLAGS += -static-libasan > endif > - > -TEST_GEN_PROGS := fchmodat2_test > - > -include ../lib.mk > diff --git a/tools/testing/selftests/hid/Makefile b/tools/testing/selftests/hid/Makefile > index 2b5ea18bde38..734a53dc8ad9 100644 > --- a/tools/testing/selftests/hid/Makefile > +++ b/tools/testing/selftests/hid/Makefile > @@ -27,7 +27,7 @@ CFLAGS += -I$(OUTPUT)/tools/include > LDLIBS += -lelf -lz -lrt -lpthread > > # Silence some warnings when compiled with clang > -ifneq ($(LLVM),) > +ifeq ($(SELFTESTS_CC_IS_CLANG),) > CFLAGS += -Wno-unused-command-line-argument > endif > > diff --git a/tools/testing/selftests/lib.mk b/tools/testing/selftests/lib.mk > index 429535816dbd..f321ad5a1d0c 100644 > --- a/tools/testing/selftests/lib.mk > +++ b/tools/testing/selftests/lib.mk > @@ -43,6 +43,21 @@ else > CC := $(CROSS_COMPILE)gcc > endif # LLVM > > +# SELFTESTS_CC_IS_CLANG allows subsystem selftests to more accurately control > +# clang-specific behavior, such as compiler options. If CC is an invocation of > +# clang in any form, then SELFTESTS_CC_IS_CLANG will be non-empty. Notes: > +# > +# 1) CC could have been set above, by inferring it from LLVM==1, or externally, > +# from the CC shell environment variable. > +# > +# 2) SELFTESTS_CC_IS_CLANG does not specify which linker is being used. However, > +# it can still help with linker options, if clang or gcc is used for the > +# linker front end. > +SELFTESTS_CC_IS_CLANG := > +ifeq ($(findstring clang,$(CC)),clang) > + SELFTESTS_CC_IS_CLANG := 1 > +endif > + > ifeq (0,$(MAKELEVEL)) > ifeq ($(OUTPUT),) > OUTPUT := $(shell pwd) > diff --git a/tools/testing/selftests/openat2/Makefile b/tools/testing/selftests/openat2/Makefile > index 185dc76ebb5f..7acb85a8f2ac 100644 > --- a/tools/testing/selftests/openat2/Makefile > +++ b/tools/testing/selftests/openat2/Makefile > @@ -3,16 +3,18 @@ > CFLAGS += -Wall -O2 -g -fsanitize=address -fsanitize=undefined > TEST_GEN_PROGS := openat2_test resolve_test rename_attack_test > > +LOCAL_HDRS += helpers.h > + > +include ../lib.mk > + > +$(TEST_GEN_PROGS): helpers.c > + > # gcc requires -static-libasan in order to ensure that Address Sanitizer's > # library is the first one loaded. However, clang already statically links the > # Address Sanitizer if -fsanitize is specified. Therefore, simply omit > # -static-libasan for clang builds. > -ifeq ($(LLVM),) > +# This check must be done after including ../lib.mk, in order to pick up the > +# correct value of SELFTESTS_CC_IS_CLANG. > +ifeq ($(SELFTESTS_CC_IS_CLANG),) > CFLAGS += -static-libasan > endif > - > -LOCAL_HDRS += helpers.h > - > -include ../lib.mk > - > -$(TEST_GEN_PROGS): helpers.c > > base-commit: 9a5cd459be8a425d70cda1fa1c89af7875a35d17 > -- > 2.45.2 > >
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