linux-kernel - Re: [PATCH 1/5] kbuild: remove unnecessary $(subst $(obj)/,,...) in modname-multi

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Date:   Thu, 8 Mar 2018 18:19:52 +0800
From:   Cao jin <caoj.fnst@...fujitsu.com>
To:     Masahiro Yamada <yamada.masahiro@...ionext.com>,
        <linux-kbuild@...r.kernel.org>
CC:     Sam Ravnborg <sam@...nborg.org>,
        Michal Marek <michal.lkml@...kovi.net>,
        Govind Singh <govinds@...eaurora.org>,
        Kalle Valo <kvalo@...eaurora.org>,
        <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 1/5] kbuild: remove unnecessary $(subst $(obj)/,,...) in
 modname-multi



On 03/08/2018 09:04 AM, Masahiro Yamada wrote:
> In the context ...
> 
>     $(obj)/%.s: $(src)/%.c FORCE
>             $(call if_changed_dep,cc_s_c)
> 
>     $(obj)/%.i: $(src)/%.c FORCE
>             $(call if_changed_dep,cpp_i_c)
> 
>     $(obj)/%.o: $(src)/%.c $(recordmcount_source) $(objtool_dep) FORCE
>             $(call cmd,force_checksrc)
>             $(call if_changed_rule,cc_o_c)
> 
>     $(obj)/%.lst: $(src)/%.c FORCE
>             $(call if_changed_dep,cc_lst_c)
> 
> '$*' returns the stem of the target (the part of '%'), so $(obj)/ has
> already been ripped off.
> 
> $(subst $(obj)/,,$*.o) is the same as $(*.o)
> 
> Signed-off-by: Masahiro Yamada <yamada.masahiro@...ionext.com>
> ---
> 
>  scripts/Makefile.lib | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/scripts/Makefile.lib b/scripts/Makefile.lib
> index 5589bae..a7e315f 100644
> --- a/scripts/Makefile.lib
> +++ b/scripts/Makefile.lib
> @@ -175,7 +175,7 @@ dtc_cpp_flags  = -Wp,-MD,$(depfile).pre.tmp -nostdinc                    \
>  
>  # Finds the multi-part object the current object will be linked into
>  modname-multi = $(sort $(foreach m,$(multi-used),\
> -		$(if $(filter $(subst $(obj)/,,$*.o), $($(m:.o=-objs)) $($(m:.o=-y))),$(m:.o=))))
> +		$(if $(filter $*.o, $($(m:.o=-objs)) $($(m:.o=-y))),$(m:.o=))))
>  
>  # Useful for describing the dependency of composite objects
>  # Usage:
> 

A subtle catch! And in my test, a debug line

    $(info $@ = $*)

in rule:

    $(obj)/%.o: $(src)/%.c xxx

does tell me it is correct. So,

Reviewed-by: Cao jin <caoj.fnst@...fujitsu.com>
-- 
Sincerely,
Cao jin