[U-Boot] [PATCH v3 20/21] Adjust dependency rules to permit per-file flags

[Mike Frysinger <vapier@gentoo.org>]

On Monday 03 October 2011 21:10:17 Simon Glass wrote:
> Hi,
> 
> On Mon, Sep 26, 2011 at 5:10 PM, Simon Glass <sjg@chromium.org> wrote:
> > The dependency rules are currently done in a shell 'for' loop. This does
> > not permit Makefile variables to adjust preprocessor flags as is done
> > with normal compile flags, using the CFLAGS_path/file.o syntax.
> > 
> > This change moves the dependency generation into the Makefile itself, and
> > permits a CPPFLAGS_path/file.o to adjust preprocessor flags on a file or
> > directory basis.
> > 
> > The CPPFLAGS_... variable is also folded into CFLAGS during the build.
> > 
> > Signed-off-by: Simon Glass <sjg@chromium.org>
> > ---
> > Changes in v3:
> > - Change U-Boot's dependency generation to permit per-file flags
> > 
> >  .gitignore |    2 +-
> >  config.mk  |    7 +++++++
> >  rules.mk   |   23 ++++++++++++-----------
> >  3 files changed, 20 insertions(+), 12 deletions(-)
> > 
> > diff --git a/.gitignore b/.gitignore
> > index dbf545f..7ba0dd9 100644
> > --- a/.gitignore
> > +++ b/.gitignore
> > @@ -39,7 +39,7 @@
> >  # Generated files
> >  #
> > 
> > -*.depend
> > +*.depend*
> >  /LOG
> >  /errlog
> >  /reloc_off
> > diff --git a/config.mk b/config.mk
> > index e2b440d..3fa9eef 100644
> > --- a/config.mk
> > +++ b/config.mk
> > @@ -277,6 +277,13 @@ export     CONFIG_SYS_TEXT_BASE PLATFORM_CPPFLAGS
> > PLATFORM_RELFLAGS CPPFLAGS CFLAGS BCURDIR = $(subst
> > $(SRCTREE)/,,$(CURDIR:$(obj)%=%))
> >  ALL_AFLAGS = $(AFLAGS) $(AFLAGS_$(BCURDIR)/$(@F)) $(AFLAGS_$(BCURDIR))
> >  ALL_CFLAGS = $(CFLAGS) $(CFLAGS_$(BCURDIR)/$(@F)) $(CFLAGS_$(BCURDIR))
> > +EXTRA_CPPFLAGS = $(CPPFLAGS_$(BCURDIR)/$(@F)) $(CPPFLAGS_$(BCURDIR))
> > +ALL_CFLAGS += $(EXTRA_CPPFLAGS)
> > +
> > +# The _DEP version uses the $< file target (for dependency generation)
> > +# See rules.mk
> > +EXTRA_CPPFLAGS_DEP = $(CPPFLAGS_$(BCURDIR)/$(addsuffix .o,$(basename
> > $<))) \ +               $(CPPFLAGS_$(BCURDIR))
> >  $(obj)%.s:     %.S
> >        $(CPP) $(ALL_AFLAGS) -o $@ $<
> >  $(obj)%.o:     %.S
> > diff --git a/rules.mk b/rules.mk
> > index d79fcd3..56b9044 100644
> > --- a/rules.mk
> > +++ b/rules.mk
> > @@ -25,17 +25,18 @@
> > 
> >  _depend:       $(obj).depend
> > 
> > -$(obj).depend: $(src)Makefile $(TOPDIR)/config.mk $(SRCS) $(HOSTSRCS)
> > -               @rm -f $@
> > -               @touch $@
> > -               @for f in $(SRCS); do \
> > -                       g=`basename $$f | sed -e
> > 's/\(.*\)\.[[:alnum:]_]/\1.o/'`; \ -                       $(CC) -M
> > $(CPPFLAGS) -MQ $(obj)$$g $$f >> $@ ; \ -               done
> > -               @for f in $(HOSTSRCS); do \
> > -                       g=`basename $$f | sed -e
> > 's/\(.*\)\.[[:alnum:]_]/\1.o/'`; \ -                       $(HOSTCC) -M
> > $(HOSTCPPFLAGS) -MQ $(obj)$$g $$f >> $@ ; \ -               done
> > +DEPS := $(basename $(patsubst %,$(obj).depend.%,$(SRCS)))
> > +
> > +$(obj).depend: $(src)Makefile $(TOPDIR)/config.mk $(DEPS) $(HOSTSRCS)
> > +       cat /dev/null $(DEPS) >$@
> > +       @for f in $(HOSTSRCS); do \
> > +               g=`basename $$f | sed -e 's/\(.*\)\.[[:alnum:]_]/\1.o/'`;
> > \ +               $(HOSTCC) -M $(HOSTCPPFLAGS) -MQ $(obj)$$g $$f >> $@ ;
> > \ +       done
> > +
> > +$(obj).depend.%:       %.c
> > +       $(CC) -M $(CPPFLAGS) $(EXTRA_CPPFLAGS_DEP) \
> > +               -MQ $(addsuffix .o,$(basename $<)) $< >$@
> > 
> >  $(HOSTOBJS): $(obj)%.o: %.c
> >        $(HOSTCC) $(HOSTCFLAGS) $(HOSTCFLAGS_$(@F))
> > $(HOSTCFLAGS_$(BCURDIR)) -o $@ $< -c --
> > 1.7.3.1
> 
> Sadly this doesn't work for two reasons:
> 
> 1. It ignores .S files (which is easy to fix)
> 
> 2. It doesn't like paths like ../common/fred.c. I can fix that with a
> patsubst I suspect.
> 
> Does anyone have better ideas on how to deal with this?

what if we move away from a single .depend file ?  most every project i see out 
there utilizes one .depend file per source.
-mike
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