Re: [PATCH] kbuild: host: use single executable for rustc -C linker

[Gary Guo]

On Wed Feb 25, 2026 at 10:28 AM GMT, Mohamad Alsadhan wrote:
> rustc's -C linker= option expects a single executable path. When
> HOSTCC contains a wrapper (e.g. "ccache gcc"), passing
> -Clinker=$(HOSTCC) results in the shell splitting the value into
> multiple words, and rustc interprets the additional word as an
> input filename:
>
>   error: multiple input filenames provided ...
>
> Use the last word of HOSTCC as the linker executable for host
> Rust tools. This preserves wrapper usage for C host tools while
> ensuring rustc receives a single executable path.

I don't think this is the right fix. Using only the last word is

(1) not what people asks for when they override HOSTCC. When a user ssays "call
ccache gcc", they don't want "gcc" to be invoked instead.
(2) not general enough. If instead of a wrapper, it's something with subcommand,
then this just breaks.
(3) going to cause surprises to people and be hard to troubleshoot when things
do not work.

I think the proper fix should be invoking a helper script with the multi-word
command be passed as environment variable which is then expanded by shell.

Best,
Gary

>
> Closes: https://github.com/Rust-for-Linux/linux/issues/1224
>
> Signed-off-by: Mohamad Alsadhan <mo@xxxxxxx>
> ---
>  scripts/Makefile.host | 9 ++++++++-
>  1 file changed, 8 insertions(+), 1 deletion(-)
>
> diff --git a/scripts/Makefile.host b/scripts/Makefile.host
> index c1dedf646..22eab2734 100644
> --- a/scripts/Makefile.host
> +++ b/scripts/Makefile.host
> @@ -87,11 +87,18 @@ hostcxx_flags  = -Wp,-MMD,$(depfile) \
>                   $(KBUILD_HOSTCXXFLAGS) $(HOST_EXTRACXXFLAGS) \
>                   $(HOSTCXXFLAGS_$(target-stem).o)
>  
> +# rustc's `-C linker=` expects a single executable path, not a command line.
> +# HOSTCC may be a multi-word command when wrapped (e.g. "ccache gcc"),
> +# which would otherwise be split by the shell and mis-parsed by rustc.
> +#
> +# Use a dedicated variable for the linker program used by host Rust tools.
> +HOSTRUSTC_LINKER ?= $(lastword $(HOSTCC))
> +
>  # `--out-dir` is required to avoid temporaries being created by `rustc` in the
>  # current working directory, which may be not accessible in the out-of-tree
>  # modules case.
>  hostrust_flags = --out-dir $(dir $@) --emit=dep-info=$(depfile) \
> -		 -Clinker-flavor=gcc -Clinker=$(HOSTCC) \
> +		 -Clinker-flavor=gcc -Clinker=$(HOSTRUSTC_LINKER) \
>  		 -Clink-args='$(call escsq,$(KBUILD_HOSTLDFLAGS))' \
>                   $(KBUILD_HOSTRUSTFLAGS) $(HOST_EXTRARUSTFLAGS) \
>                   $(HOSTRUSTFLAGS_$(target-stem))