linux-kernel - Re: [PATCH 04/10] kbuild: add %.lex.c and %.tab.[ch] to 'targets' automatically

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Date:   Fri, 23 Mar 2018 18:22:36 -0700
From:   Frank Rowand <frowand.list@...il.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>,
        linux-kernel@...r.kernel.org, Arnd Bergmann <arnd@...db.de>,
        Laurent Pinchart <laurent.pinchart@...asonboard.com>,
        Frank Rowand <frank.rowand@...y.com>,
        Geert Uytterhoeven <geert@...ux-m68k.org>
Subject: Re: [PATCH 04/10] kbuild: add %.lex.c and %.tab.[ch] to 'targets'
 automatically

On 03/23/18 06:04, Masahiro Yamada wrote:
> Files generated by if_changed* must be added to 'targets' to include
> *.cmd files.  Otherwise, they would be regenerated every time.
> 
> The build system automatically adds objects to 'targets' where
> appropriate, such as obj-y, extra-y, etc. but does nothing for
> intermediate files.  So, each Makefile needs to add them by itself.
> 
> There are some common cases where objects are generated by chained
> rules.  Lexers and parsers are compiled like follows:
> 
>    %.lex.o <- %.lex.c <- %.l
>    %.tab.o <- %.tab.c <- %.y
> 
> They are common patterns, so it is reasonable to take care of them
> in the core Makefile instead of requiring each Makefile to do so.
> 
> At this moment, you cannot delete 'target += zconf.lex.c' because
> zconf.lex.c is included from zconf.tab.c instead of being compiled.
> This will be possible with further refactoring in the future.
> 
> Signed-off-by: Masahiro Yamada <yamada.masahiro@...ionext.com>

Acked-by: Frank Rowand <frowand.list@...il.com>

-Frank

> ---
> 
>  scripts/Makefile.build    | 11 +++++++++++
>  scripts/dtc/Makefile      |  3 ---
>  scripts/genksyms/Makefile |  2 --
>  scripts/kconfig/Makefile  |  2 +-
>  4 files changed, 12 insertions(+), 6 deletions(-)
> 
> diff --git a/scripts/Makefile.build b/scripts/Makefile.build
> index 77cce68..36f7990 100644
> --- a/scripts/Makefile.build
> +++ b/scripts/Makefile.build
> @@ -538,6 +538,17 @@ $(call multi_depend, $(multi-used-m), .o, -objs -y -m)
>  targets += $(multi-used-m)
>  targets := $(filter-out $(PHONY), $(targets))
>  
> +# Add intermediate targets:
> +# When building objects with specific suffix patterns, add intermediate
> +# targets that the final targets are derived from.
> +intermediate_targets = $(foreach sfx, $(2), \
> +				$(patsubst %$(strip $(1)),%$(sfx), \
> +					$(filter %$(strip $(1)), $(targets))))
> +# %.lex.o <- %.lex.c <- %.l
> +# %.tab.o <- %.tab.[ch] <- %.y
> +targets += $(call intermediate_targets, .lex.o, .lex.c) \
> +	   $(call intermediate_targets, .tab.o, .tab.c .tab.h)
> +
>  # Descending
>  # ---------------------------------------------------------------------------
>  
> diff --git a/scripts/dtc/Makefile b/scripts/dtc/Makefile
> index d17ba64..9cac65b 100644
> --- a/scripts/dtc/Makefile
> +++ b/scripts/dtc/Makefile
> @@ -27,6 +27,3 @@ HOSTCFLAGS_dtc-parser.tab.o := $(HOSTCFLAGS_DTC)
>  
>  # dependencies on generated files need to be listed explicitly
>  $(obj)/dtc-lexer.lex.o: $(obj)/dtc-parser.tab.h
> -
> -# generated files need to include *.cmd
> -targets := dtc-lexer.lex.c dtc-parser.tab.c dtc-parser.tab.h
> diff --git a/scripts/genksyms/Makefile b/scripts/genksyms/Makefile
> index f4749e8..aeefd47 100644
> --- a/scripts/genksyms/Makefile
> +++ b/scripts/genksyms/Makefile
> @@ -32,5 +32,3 @@ HOSTCFLAGS_lex.lex.o := -I$(src)
>  
>  # dependencies on generated files need to be listed explicitly
>  $(obj)/lex.lex.o: $(obj)/parse.tab.h
> -
> -targets := lex.lex.c parse.tab.c parse.tab.h
> diff --git a/scripts/kconfig/Makefile b/scripts/kconfig/Makefile
> index 1dcd797..5def877 100644
> --- a/scripts/kconfig/Makefile
> +++ b/scripts/kconfig/Makefile
> @@ -207,7 +207,7 @@ gconf-objs	:= gconf.o zconf.tab.o
>  
>  hostprogs-y := conf nconf mconf kxgettext qconf gconf
>  
> -targets		+= zconf.tab.c zconf.lex.c
> +targets		+= zconf.lex.c
>  clean-files	:= qconf.moc .tmp_qtcheck .tmp_gtkcheck
>  clean-files	+= gconf.glade.h
>  clean-files     += config.pot linux.pot
>