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Date:   Tue, 1 Feb 2022 09:01:52 -0700
From:   Nathan Chancellor <nathan@kernel.org>
To:     Jean-Philippe Brucker <jean-philippe@linaro.org>
Cc:     ndesaulniers@google.com, llvm@lists.linux.dev, bpf@vger.kernel.org,
        andrii@kernel.org, quentin@isovalent.com
Subject: Re: [PATCH] tools: Ignore errors from `which' when searching a GCC
 toolchain
Message-ID: <YflZcEjaPoN8G84c@dev-arch.archlinux-ax161>
References: <20220201093119.1713207-1-jean-philippe@linaro.org>
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On Tue, Feb 01, 2022 at 09:31:20AM +0000, Jean-Philippe Brucker wrote:
> When cross-building tools with clang, we run `which $(CROSS_COMPILE)gcc`
> to detect whether a GCC toolchain provides the standard libraries. It is
> only a helper because some distros put libraries where LLVM does not
> automatically find them. On other systems, LLVM detects the libc
> automatically and does not need this. There, it is completely fine not
> to have a GCC at all, but some versions of `which' display an error when
> the command is not found:
> 
> 	which: no aarch64-linux-gnu-gcc in ($PATH)
> 
> Since the error can safely be ignored, throw it to /dev/null.
> 
> Fixes: cebdb7374577 ("tools: Help cross-building with clang")
> Reported-by: Nathan Chancellor <nathan@kernel.org>
> Signed-off-by: Jean-Philippe Brucker <jean-philippe@linaro.org>

Thanks a lot for the quick fix!

Reviewed-by: Nathan Chancellor <nathan@kernel.org>
Tested-by: Nathan Chancellor <nathan@kernel.org>

It would be nice if this could go in via bpf, as cebdb7374577 was merged
in 5.17-rc1.

> ---
>  tools/scripts/Makefile.include | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/tools/scripts/Makefile.include b/tools/scripts/Makefile.include
> index b0be5f40a3f1..79d102304470 100644
> --- a/tools/scripts/Makefile.include
> +++ b/tools/scripts/Makefile.include
> @@ -90,7 +90,7 @@ EXTRA_WARNINGS += -Wstrict-aliasing=3
>  
>  else ifneq ($(CROSS_COMPILE),)
>  CLANG_CROSS_FLAGS := --target=$(notdir $(CROSS_COMPILE:%-=%))
> -GCC_TOOLCHAIN_DIR := $(dir $(shell which $(CROSS_COMPILE)gcc))
> +GCC_TOOLCHAIN_DIR := $(dir $(shell which $(CROSS_COMPILE)gcc 2>/dev/null))
>  ifneq ($(GCC_TOOLCHAIN_DIR),)
>  CLANG_CROSS_FLAGS += --prefix=$(GCC_TOOLCHAIN_DIR)$(notdir $(CROSS_COMPILE))
>  CLANG_CROSS_FLAGS += --sysroot=$(shell $(CROSS_COMPILE)gcc -print-sysroot)
> -- 
> 2.34.1
> 
>