Re: [PATCH] kbuild: install-extmod-build: Properly fix CC expansion when ccache is used

[Nathan Chancellor <nathan@kernel.org>]

On Mon, Nov 10, 2025 at 12:26:31AM +0200, Abel Vesa wrote:
> Currently, when cross-compiling and ccache is used, the expanding of CC
> turns out to be without any quotes, leading to the following error:
> 
> make[4]: *** No rule to make target 'aarch64-linux-gnu-gcc'.  Stop.
> make[3]: *** [Makefile:2164: run-command] Error 2
> 
> And it makes sense, because after expansion it ends up like this:
> 
> make run-command KBUILD_RUN_COMMAND=+$(MAKE) \
> HOSTCC=ccache aarch64-linux-gnu-gcc VPATH= srcroot=. $(build)= ...

Yup, good old shell quoting... :(

> So add another set of double quotes, this time escaped, to make sure the
> aarch64-linux-gnu-gcc isn't expanded to something that looks like an
> entirely separate target.
> 
> Fixes: 140332b6ed72 ("kbuild: fix linux-headers package build when $(CC) cannot link userspace")
> Signed-off-by: Abel Vesa <abel.vesa@linaro.org>
> ---
>  scripts/package/install-extmod-build | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/scripts/package/install-extmod-build b/scripts/package/install-extmod-build
> index 054fdf45cc37a8717444b8094daf3e1150a8ccf5..6cce5c41552d520bf069487352fd26417b0b3899 100755
> --- a/scripts/package/install-extmod-build
> +++ b/scripts/package/install-extmod-build
> @@ -63,7 +63,7 @@ if [ "${CC}" != "${HOSTCC}" ]; then
>  	# Clear VPATH and srcroot because the source files reside in the output
>  	# directory.
>  	# shellcheck disable=SC2016 # $(MAKE) and $(build) will be expanded by Make
> -	"${MAKE}" run-command KBUILD_RUN_COMMAND='+$(MAKE) HOSTCC='"${CC}"' VPATH= srcroot=. $(build)='"$(realpath --relative-to=. "${destdir}")"/scripts
> +	"${MAKE}" run-command KBUILD_RUN_COMMAND='+$(MAKE) HOSTCC='\""${CC}"\"' VPATH= srcroot=. $(build)='"$(realpath --relative-to=. "${destdir}")"/scripts

Can we avoid the need for escaping the " by just moving it to the other
side of the '?

  "${MAKE}" run-command KBUILD_RUN_COMMAND='+$(MAKE) HOSTCC="'"${CC}"'" VPATH= srcroot=. $(build)='"$(realpath --relative-to=. "${destdir}")"/scripts

This whole command is really hard to read but I don't really see an
obvious way to simplify it.

>  
>  	rm -f "${destdir}/scripts/Kbuild"
>  fi
> 
> ---
> base-commit: 9c0826a5d9aa4d52206dd89976858457a2a8a7ed
> change-id: 20251109-kbuild-install-extmod-build-fix-cc-expand-third-try-2cb1540cadbf
> 
> Best regards,
> -- 
> Abel Vesa <abel.vesa@linaro.org>
>