Messages in this thread | | | Date | Tue, 28 Jul 2020 12:09:41 -0300 | From | Arnaldo Carvalho de Melo <> | Subject | Re: [PATCH 1/3] tools build feature: Use CC and CXX from parent |
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Em Tue, Jul 28, 2020 at 04:42:02PM +0200, Jiri Olsa escreveu: > On Sun, Jul 26, 2020 at 09:08:14PM -0700, Thomas Hebb wrote: > > commit c8c188679ccf ("tools build: Use the same CC for feature detection > > and actual build") changed these assignments from unconditional (:=) to > > conditional (?=) so that they wouldn't clobber values from the > > environment. However, conditional assignment does not work properly for > > variables that Make implicitly sets, among which are CC and CXX. To > > quote tools/scripts/Makefile.include, which handles this properly: > > > > # Makefiles suck: This macro sets a default value of $(2) for the > > # variable named by $(1), unless the variable has been set by > > # environment or command line. This is necessary for CC and AR > > # because make sets default values, so the simpler ?= approach > > # won't work as expected. > > > > In other words, the conditional assignments will not run even if the > > variables are not overridden in the environment; Make will set CC to > > "cc" and CXX to "g++" when it starts[1], meaning the variables are not > > empty by the time the conditional assignments are evaluated. This breaks > > cross-compilation when CROSS_COMPILE is set but CC isn't, since "cc" > > gets used for feature detection instead of the cross compiler (and > > likewise for CXX). > > > > To fix the issue, just pass down the values of CC and CXX computed by > > the parent Makefile, which gets included by the Makefile that actually > > builds whatever we're detecting features for and so is guaranteed to > > have good values. This is a better solution anyway, since it means we > > aren't trying to replicate the logic of the parent build system and so > > don't risk it getting out of sync. > > > > Leave PKG_CONFIG alone, since 1) there's no common logic to compute it > > in Makefile.include, and 2) it's not an implicit variable, so > > conditional assignment works properly. > > looks good, I wonder we might need it also for CLANG in the future > > Acked-by: Jiri Olsa <jolsa@redhat.com>
Thanks for checking, I'll add it to the mix and see how it goes with the container tests.
- Arnaldo
> thanks, > jirka > > > > > [1] https://www.gnu.org/software/make/manual/html_node/Implicit-Variables.html > > > > Fixes: c8c188679ccf ("tools build: Use the same CC for feature detection and actual build") > > Signed-off-by: Thomas Hebb <tommyhebb@gmail.com> > > --- > > > > tools/build/Makefile.feature | 2 +- > > tools/build/feature/Makefile | 2 -- > > 2 files changed, 1 insertion(+), 3 deletions(-) > > > > diff --git a/tools/build/Makefile.feature b/tools/build/Makefile.feature > > index cb152370fdef..774f0b0ca28a 100644 > > --- a/tools/build/Makefile.feature > > +++ b/tools/build/Makefile.feature > > @@ -8,7 +8,7 @@ endif > > > > feature_check = $(eval $(feature_check_code)) > > define feature_check_code > > - feature-$(1) := $(shell $(MAKE) OUTPUT=$(OUTPUT_FEATURES) CFLAGS="$(EXTRA_CFLAGS) $(FEATURE_CHECK_CFLAGS-$(1))" CXXFLAGS="$(EXTRA_CXXFLAGS) $(FEATURE_CHECK_CXXFLAGS-$(1))" LDFLAGS="$(LDFLAGS) $(FEATURE_CHECK_LDFLAGS-$(1))" -C $(feature_dir) $(OUTPUT_FEATURES)test-$1.bin >/dev/null 2>/dev/null && echo 1 || echo 0) > > + feature-$(1) := $(shell $(MAKE) OUTPUT=$(OUTPUT_FEATURES) CC=$(CC) CXX=$(CXX) CFLAGS="$(EXTRA_CFLAGS) $(FEATURE_CHECK_CFLAGS-$(1))" CXXFLAGS="$(EXTRA_CXXFLAGS) $(FEATURE_CHECK_CXXFLAGS-$(1))" LDFLAGS="$(LDFLAGS) $(FEATURE_CHECK_LDFLAGS-$(1))" -C $(feature_dir) $(OUTPUT_FEATURES)test-$1.bin >/dev/null 2>/dev/null && echo 1 || echo 0) > > endef > > > > feature_set = $(eval $(feature_set_code)) > > diff --git a/tools/build/feature/Makefile b/tools/build/feature/Makefile > > index b1f0321180f5..93b590d81209 100644 > > --- a/tools/build/feature/Makefile > > +++ b/tools/build/feature/Makefile > > @@ -74,8 +74,6 @@ FILES= \ > > > > FILES := $(addprefix $(OUTPUT),$(FILES)) > > > > -CC ?= $(CROSS_COMPILE)gcc > > -CXX ?= $(CROSS_COMPILE)g++ > > PKG_CONFIG ?= $(CROSS_COMPILE)pkg-config > > LLVM_CONFIG ?= llvm-config > > CLANG ?= clang > > -- > > 2.27.0 > > >
--
- Arnaldo
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