Re: [PATCH] Makefile: Improve compiler header dependency check

[Jonathan Nieder <jrnieder@gmail.com>]

David Aguilar wrote:

> I fired up git's next branch on a mac laptop where I
> have a config.mak that builds universal git binaries:
>
> CFLAGS = -arch i386 -arch x86_64
>
> This configuration broke when 111ee18c31f9bac9436426399355facc79238566
> was merged into next.

Good catch; thanks.  This information would be useful for the commit
message.

> gcc cannot generate header dependencies when
> multiple -arch statements are used

Sounds like a bug.  Any idea why it behaves that way?  What error message
does it write?

If it is a bug, it might be worth reporting this to the gcc devs while
at it.

[...]
> --- a/Makefile
> +++ b/Makefile
> @@ -1251,7 +1251,8 @@ USE_COMPUTED_HEADER_DEPENDENCIES =
>  else
>  ifndef COMPUTE_HEADER_DEPENDENCIES
>  dep_check = $(shell sh -c \
> -	'$(CC) -c -MF /dev/null -MMD -MP -x c /dev/null -o /dev/null 2>&1; \
> +	'$(CC) -c -MF /dev/null -MMD -MP -x c /dev/null -o /dev/null \
> +	$(ALL_CFLAGS) $(EXTRA_CPPFLAGS) 2>&1; \
>  	echo $$?')

EXTRA_CPPFLAGS is a target-specific variable and would always be empty,
So I think this would be clearer without.

While we're touching this line, do you know if the "sh -c" is
necessary?  I would expect $(shell ...) to run its arguments in a
shell.

Thanks --- despite the nitpicks above, this one looks good.
Jonathan