Re: [PATCH] tools/build: make in-target rule robust against too long argument error

[Ian Rogers]

On Mon, Jul 28, 2025 at 2:31 AM <changqing.li@xxxxxxxxxxxxx> wrote:
>
> From: Changqing Li <changqing.li@xxxxxxxxxxxxx>
>
> The command length of in-target scales with the depth of the directory
> times the number of objects in the Makefile. When there are many
> objects, and O=[absolute_path] is set, and the absolute_path is
> relatively long. It is possile that this line "$(call
> if_changed,$(host)ld_multi)" will report error:
> "make[4]: /bin/sh: Argument list too long"
>
> For example, build perf tools with O=/long/output/path
>
> Like built-in.a and *.mod rules in scripts/Makefile.build, add
> $(objpredix)/ by the shell command instead of by Make's builtin
> function.
>
> Signed-off-by: Changqing Li <changqing.li@xxxxxxxxxxxxx>

Thanks Changqing, the change makes sense to me. The printf is pushing
the values into xargs rather than using $^ with ld. I've tried
reproducing the error to test your fix by creating long directory
names in /tmp and then passing them to O=. I've not been able to do
this. Could you send a reproduction for me to test?

Thanks,
Ian

> ---
>  tools/build/Makefile.build | 6 ++++--
>  1 file changed, 4 insertions(+), 2 deletions(-)
>
> diff --git a/tools/build/Makefile.build b/tools/build/Makefile.build
> index 3584ff308607..39066a3ef2fc 100644
> --- a/tools/build/Makefile.build
> +++ b/tools/build/Makefile.build
> @@ -70,11 +70,13 @@ quiet_cmd_gen = GEN     $@
>  # If there's nothing to link, create empty $@ object.
>  quiet_cmd_ld_multi = LD      $@
>        cmd_ld_multi = $(if $(strip $(obj-y)),\
> -                     $(LD) -r -o $@  $(filter $(obj-y),$^),rm -f $@; $(AR) rcs $@)
> +                     printf "$(objprefix)%s " $(patsubst $(objprefix)%,%,$(filter $(obj-y),$^)) | \
> +                     xargs $(LD) -r -o $@,rm -f $@; $(AR) rcs $@)
>
>  quiet_cmd_host_ld_multi = HOSTLD  $@
>        cmd_host_ld_multi = $(if $(strip $(obj-y)),\
> -                          $(HOSTLD) -r -o $@  $(filter $(obj-y),$^),rm -f $@; $(HOSTAR) rcs $@)
> +                          printf "$(objprefix)%s " $(patsubst $(objprefix)%,%,$(filter $(obj-y),$^)) | \
> +                          xargs $(HOSTLD) -r -o $@,rm -f $@; $(HOSTAR) rcs $@)
>
>  ifneq ($(filter $(obj),$(hostprogs)),)
>    host = host_
> --
> 2.34.1
>