Re: [PATCH] kbuild: add Makefile snippet to list compiled files

[Michal Marek]

On Wed, Dec 07, 2011 at 07:25:37AM +0100, Christian Dietrich wrote:
> To list the compilation units compiled by the current configuration the
> scripts/Makefile.list can be executed. It supports:
> 
> - printing of all compilation units
> - all directories considered for compilation units
> - test if a given file is compiled by the configuration
> - use a different auto.conf
> 
> Signed-off-by: Christian Dietrich <christian.dietrich@xxxxxxxxxxxxxxxxxxxxxxxxxx>
> ---
>  Hi,
> 
>  the following patch is a result of our research work at VAMOS[1],
>  where we try to examine the perconditions under which a file is
>  compiled into the linux kernel.
> 
>  While working on this, we needed a way to get all compilation units,
>  which are compiled with the current configuration. And since this
>  might be useful for others, I think it would be great to have this
>  possibility in the mainline kernel.

I agree it would be useful, I have just a couple of comments.

- The user interface should either be a target of the main makefile or
  a script. The make -f call seems a bit clumsy to me.
- You should perhaps start with less features. E.g. overriding the
  location of auto.conf is hardly needed, also the compiled= option adds
  some code, while the goal could be achieved by simply grepping the full
  output.
- The deficiency of the approach is that it misses directories that are
  only visited by an explicit make call in another makefile. An example
  is the arch/x86/boot directory on x86. This should be at least
  documented.
- The output can contain duplicates, if a object file is listed twice in
  a Makefile (e.g. arch/x86/kernel/apic/ipi.o with x86_64 defconfig)
- lib-y is not considered.
- In general, it would be good to do a comparison between the output of
  your Makefile and find -name '*.o' after a build and either fix or
  document the differences.


> +# Read auto.conf if it exists, otherwise ignore
> +ifeq ($(auto_conf),)
> +-include include/config/auto.conf
> +else
> +include $(auto_conf)
> +endif

auto.conf missing should be considered fatal.


> +# The filename Kbuild has precedence over Makefile
> +kbuild-dir := $(if $(filter /%,$(src)),$(src),$(srctree)/$(src))
> +include $(if $(wildcard $(kbuild-dir)/Kbuild), $(kbuild-dir)/Kbuild, $(kbuild-dir)/Makefile)
> +
> +# Figure out what we need to build from the various variables
> +# ==========================================================================
> +
> +__subdir-y	:= $(patsubst %/,%,$(filter %/, $(obj-y)))
> +subdir-y	+= $(__subdir-y)
> +__subdir-m	:= $(patsubst %/,%,$(filter %/, $(obj-m)))
> +subdir-m	+= $(__subdir-m)
> +__subdir-n	:= $(patsubst %/,%,$(filter %/, $(obj-n)))
> +subdir-n	+= $(__subdir-n)
> +__subdir-	:= $(patsubst %/,%,$(filter %/, $(obj-)))
> +subdir-		+= $(__subdir-)
> +
> +# Subdirectories we need to descend into
> +subdir-ym	:= $(sort $(subdir-y) $(subdir-m))
> +subdir-ymn      := $(sort $(subdir-ym) $(subdir-n) $(subdir-))

You are assiging variables that are immediatelly reassigned by
Makefile.lib (if there is a special reason that I'm missing, please
explain in a comment).

Michal
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