linux-kernel - Re: [PATCH] kbuild: revive "Entering directory" for Make >= 4.4.1

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Date:   Wed, 14 Jun 2023 22:33:59 +0200
From:   Nicolas Schier <nicolas@...sle.eu>
To:     Masahiro Yamada <masahiroy@...nel.org>
Cc:     linux-kbuild@...r.kernel.org, linux-kernel@...r.kernel.org,
        David Howells <dhowells@...hat.com>,
        Nathan Chancellor <nathan@...nel.org>,
        Nick Desaulniers <ndesaulniers@...gle.com>
Subject: Re: [PATCH] kbuild: revive "Entering directory" for Make >= 4.4.1

On Sun 11 Jun 2023 01:17:11 +0900, Masahiro Yamada wrote:
> With commit 9da0763bdd82 ("kbuild: Use relative path when building in
> a subdir of the source tree"), compiler messages in out-of-tree builds
> include relative paths, which are relative to the build directory, not
> the directory where make was started.
> 
> To help IDEs/editors find the source files, Kbuild lets GNU Make print
> "Entering directory ..." when it changes the working directory. It has
> been working fine for a long time, but David reported it is broken with
> GNU Make 4.4.1.
> 
> The behavior was changed by GNU Make commit 8f9e7722ff0f ("[SV 63537]
> Fix setting -w in makefiles"). Previously, setting --no-print-directory
> to MAKEFLAGS only affected child makes, but it is now interpreted in
> the current make as soon as it is set.
> 
> [test code]
> 
>   $ cat /tmp/Makefile
>   MAKEFLAGS += --no-print-directory
>   all: ; :
> 
> [before 8f9e7722ff0f]
> 
>   $ make -C /tmp
>   make: Entering directory '/tmp'
>   :
>   make: Leaving directory '/tmp'
> 
> [after 8f9e7722ff0f]
> 
>   $ make -C /tmp
>   :
> 
> This commit restores the previous behavior for GNU Make >= 4.4.1.
> 
> Reported-by: David Howells <dhowells@...hat.com>
> Closes: https://lore.kernel.org/all/2427604.1686237298@warthog.procyon.org.uk/
> Signed-off-by: Masahiro Yamada <masahiroy@...nel.org>
> ---
> 
>  Makefile | 16 ++++++++++++++--
>  1 file changed, 14 insertions(+), 2 deletions(-)
> 
> diff --git a/Makefile b/Makefile
> index cc3fe09c4dec..9868186deb66 100644
> --- a/Makefile
> +++ b/Makefile
> @@ -191,7 +191,7 @@ endif # ifneq ($(KBUILD_OUTPUT),)
>  
>  ifeq ($(abs_objtree),$(CURDIR))
>  # Suppress "Entering directory ..." unless we are changing the work directory.
> -MAKEFLAGS += --no-print-directory
> +no-print-directory := --no-print-directory
>  else
>  need-sub-make := 1
>  endif
> @@ -203,6 +203,15 @@ ifneq ($(words $(subst :, ,$(abs_srctree))), 1)
>  $(error source directory cannot contain spaces or colons)
>  endif
>  
> +ifneq ($(filter jobserver-fifo,$(.FEATURES)),) # test $(MAKE_VERSION) >= 4.4

In scripts/Kbuild.include, we use $(intcmp) to check against Make 
version >= 4.4, cp. commit fccb3d3eda8d ("kbuild: add 
test-{ge,gt,le,lt} macros", 2022-12-11).  Might it make sense to use 
the same test here too?

> +ifeq ($(filter 4.4,$(MAKE_VERSION)),)
> +# With GNU Make >= 4.4.1, a change in MAKEFLAGS takes effect as soon as it is
> +# set. Run __sub-make all the time so that we can pass --no-print-directory
> +# via the command line.
> +need-sub-make := 1
> +endif
> +endif
> +
>  ifneq ($(filter 3.%,$(MAKE_VERSION)),)
>  # 'MAKEFLAGS += -rR' does not immediately become effective for GNU Make 3.x
>  # We need to invoke sub-make to avoid implicit rules in the top Makefile.
> @@ -223,7 +232,8 @@ $(filter-out $(this-makefile), $(MAKECMDGOALS)) __all: __sub-make
>  
>  # Invoke a second make in the output directory, passing relevant variables
>  __sub-make:
> -	$(Q)$(MAKE) -C $(abs_objtree) -f $(abs_srctree)/Makefile $(MAKECMDGOALS)
> +	$(Q)$(MAKE) $(no-print-directory) -C $(abs_objtree) \
> +	-f $(abs_srctree)/Makefile $(MAKECMDGOALS)

I like that solution, thanks!

Reviewed-by: Nicolas Schier <nicolas@...sle.eu>

>  
>  endif # need-sub-make
>  endif # sub_make_done
> @@ -234,6 +244,8 @@ ifeq ($(need-sub-make),)
>  # Do not print "Entering directory ...",
>  # but we want to display it when entering to the output directory
>  # so that IDEs/editors are able to understand relative filenames.
> +# This line is needed to allow Make < 4.4.1 to skip __sub-make.
> +# The newer Make versions runs __sub-make before seeing this line.
>  MAKEFLAGS += --no-print-directory
>  
>  ifeq ($(abs_srctree),$(abs_objtree))
> -- 
> 2.39.2

-- Nicolas Schier

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