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From:   Zhangjin Wu <falcon@tinylab.org>
To:     w@1wt.eu
Cc:     arnd@arndb.de, falcon@tinylab.org, linux-kernel@vger.kernel.org,
        linux-kselftest@vger.kernel.org, tanyuan@tinylab.org,
        thomas@t-8ch.de
Subject: Re: [PATCH v6 7/8] selftests/nolibc: allow customize CROSS_COMPILE by architecture
Date:   Sun,  6 Aug 2023 18:16:36 +0800
Message-Id: <20230806101636.14407-1-falcon@tinylab.org>
In-Reply-To: <20230806100410.GC10627@1wt.eu>
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It uses 'eval $(1) = $(2)' style, no real 'override' as the name shows
;-)

> > 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.
>

A simple tests shows, we are able to simply move the include after our
customize lines:

    diff --git a/tools/testing/selftests/nolibc/Makefile b/tools/testing/selftests/nolibc/Makefile
    index 1f7c36fbe083..ed21dc393dc0 100644
    --- a/tools/testing/selftests/nolibc/Makefile
    +++ b/tools/testing/selftests/nolibc/Makefile
    @@ -1,6 +1,4 @@
     # SPDX-License-Identifier: GPL-2.0
    -# Makefile for nolibc tests
    -include ../../../scripts/Makefile.include
     # We need this for the "cc-option" macro.
     include ../../../build/Build.include

    diff --git a/tools/testing/selftests/nolibc/Makefile b/tools/testing/selftests/nolibc/Makefile
    index 228a95e65113..91a2a546954c 100644
    --- a/tools/testing/selftests/nolibc/Makefile
    +++ b/tools/testing/selftests/nolibc/Makefile
    @@ -55,6 +55,12 @@ IMAGE_loongarch  = arch/loongarch/boot/vmlinuz.efi
     IMAGE            = $(IMAGE_$(XARCH))
     IMAGE_NAME       = $(notdir $(IMAGE))

    +# CROSS_COMPILE: cross toolchain prefix by architecture
    +CROSS_COMPILE           ?= $(CROSS_COMPILE_$(XARCH))
    +
    +# make sure CC is prefixed with CROSS_COMPILE
    +include ../../../scripts/Makefile.include

Thanks,
Zhangjin

> Willy