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