On Sun, Aug 06, 2023 at 05:39:21PM +0800, Zhangjin Wu wrote: > > > +# CROSS_COMPILE: cross toolchain prefix by architecture > > > +CROSS_COMPILE ?= $(CROSS_COMPILE_$(XARCH)) > > > + > > > +# make sure CC is prefixed with CROSS_COMPILE > > > +$(call allow-override,CC,$(CROSS_COMPILE)gcc) > > > + > > > > Note that I feared that it would break my "CC=gcc-5.5.0" and so on but > > fortunately it did not. However I don't understand what it tries to do > > nor the problem it tries to solve (even the commit message is quite > > unclear to me). I'm leaving it aside anyway but I wanted to let you > > know. > > > > Thanks you for this note, will add it as a test case in our v2. > > These places require the '$(CC)' prefixed with $(CROSS_COMPILE): > > $ grep ")\$(CC)" tools/testing/selftests/nolibc/Makefile > $(QUIET_CC)$(CC) $(CFLAGS) $(LDFLAGS) -o $@ \ > $(QUIET_CC)$(CC) $(CFLAGS) $(LDFLAGS) -o $@ \ > $(QUIET_CC)$(CC) -o $@ $< > > When CROSS_COMPILE come from command line, the first lines we included have > the CROSS_COMPILE knowledge and will add right prefix for CC: > > # Makefile for nolibc tests > include ../../../scripts/Makefile.include > > But the customized $(CROSS_COMPILE) must be added from the XARCH lines, then, > differs from the ones passed from command line, the above lines (before XARCH) > will have no CROSS_COMPILE knowledge, the CC therefore will have no prefix. > > CROSS_COMPILE=xxx <= before, from command line > > include ../../../scripts/Makefile.include <= CC get the right CROSS_COMPILE prefix > > XARCH = $(or $(XARCH_$(ARCH)),$(ARCH)) <= XARCH here > > CROSS_COMPILE ?= $(CROSS_COMPILE_$(XARCH)) <= after, customize ourselves > (call allow-override,CC,$(CROSS_COMPILE)gcc) <= CC have no right prefix here > > $(QUIET_CC)$(CC) $(CFLAGS) $(LDFLAGS) -o $@ \ > > So, we must add the prefix to CC ourselves after the CROSS_COMPILE lines we > customized, the 'allow-override' helper is also from > ../../../scripts/Makefile.include. OK, I feared it would overwrite the command-line one. > But you did find a bug above, we should include it again here to avoid not > break the possibility of using llvm (still require to check if there are some > other regressions): > > include ../../../scripts/Makefile.include > > And I have further found there is another cc-cross-prefix helper from: > > $ grep cc-cross-prefix -ur scripts/ > scripts/Makefile.compiler:# cc-cross-prefix > scripts/Makefile.compiler:# Usage: CROSS_COMPILE := $(call cc-cross-prefix, m68k-linux-gnu- m68k-linux-) > scripts/Makefile.compiler:cc-cross-prefix = $(firstword $(foreach c, $(1), \ > > So, we are able to search the toolchains from Arnd's, local toolchains and ..., > may not need to force users to use which one, I will do more tests on it. > > Please don't merge this patch too, to avoid break anything, let's tune it > carefully in our v2 and delay the whole stuff to v6.7. OK. Note that in the end it might be less difficult to try to set CROSS_COMPILE *before* including the general include instead of after: we could preset CROSS_COMPILE based on the ARCH/XARCH we know at this step, as this is not expected to rely on auto-detection. Willy
