Re: [RFC] Replicate src dir in build dir

[Simon Marchi <simon dot marchi at polymtl dot ca>]

On 2017-09-20 10:02, Yao Qi wrote:
> > > @@ -2941,9 +2949,9 @@ ifeq ($(DEPMODE),depmode=gcc3)
> > >  # into place if the compile succeeds.  We need this because gcc does
> > >  # not atomically write the dependency output file.
> > >  override COMPILE.post = -c -o $@ -MT $@ -MMD -MP \
> > > -	-MF $(DEPDIR)/$(basename $(@F)).Tpo
> > > -override POSTCOMPILE = @mv $(DEPDIR)/$(basename $(@F)).Tpo \
> > > -	$(DEPDIR)/$(basename $(@F)).Po
> > > +	-MF $(@D)/$(DEPDIR)/$(@F).Tpo
> > > +override POSTCOMPILE = @mv $(@D)/$(DEPDIR)/$(@F).Tpo \
> > > +	$(@D)/$(DEPDIR)/$(@F).Po
> > >  else
> > >  override COMPILE.pre = source='$<' object='$@' libtool=no \
> > >  	DEPDIR=$(DEPDIR) $(DEPMODE) $(depcomp) $(CC)
> >
> > I have never tested it, but I assume the "depcomp" mode of dependency
> > management will have to be updated too.
>
> I don't understand this comment.  The only change in on dependency
> tracking is that .Po file is moved to a new place (.deps/amd64.Po ->
> ./arch/.deps/amd64.o.Po).  The file contents don't change.
>
> $ diff -u .deps/amd64.Po ./arch/.deps/amd64.o.Po
> --- .deps/amd64.Po	2017-09-20 07:57:04.903381133 +0000
> +++ ./arch/.deps/amd64.o.Po	2017-09-20 07:40:35.995718460 +0000
> @@ -1,4 +1,4 @@
> -amd64.o: ../../binutils-gdb/gdb/arch/amd64.c \
> +arch/amd64.o: ../../binutils-gdb/gdb/arch/amd64.c \
>   ../../binutils-gdb/gdb/arch/amd64.h 
> ../../binutils-gdb/gdb/arch/tdesc.h \
>   build-gnulib/import/stdint.h 
> ../../binutils-gdb/gdb/common/x86-xstate.h \
>   build-gnulib/import/stdlib.h \

I was wondering if this line needed changing

override COMPILE.pre = source='$<' object='$@' libtool=no \
	DEPDIR=$(DEPDIR) $(DEPMODE) $(depcomp) $(CC)

In particular, is DEPDIR treated as relative to the created object file 
or relative to the current working directory by depcomp.  I honestly 
don't even know when this actually used.

Simon