Re: [Qemu-devel] Re: [PATCH] fix tool/libuser makefile race

[Andreas Färber]

Hey,

Am 18.12.2009 um 17:16 schrieb Juan Quintela:

> Paolo Bonzini <address@hidden> wrote:
> > I just had this race happen on me while building qemu.  The  
> > problematic
> > file in my case was cutils.o.  I'm using GNU make's order-only
> > dependencies to avoid that "make recurse-all" builds the tools as  
> > well.
> >
> > Signed-off-by: Paolo Bonzini <address@hidden>
> >
> > Signed-off-by: Paolo Bonzini <address@hidden>
> > ---
> > Makefile |    5 ++++-
> > 1 files changed, 4 insertions(+), 1 deletions(-)
> >
> > diff --git a/Makefile b/Makefile
> > index d555bb2..373a861 100644
> > --- a/Makefile
> > +++ b/Makefile
> > @@ -79,7 +79,10 @@ romsubdir-%:
> >
> > ALL_SUBDIRS=$(TARGET_DIRS) $(patsubst %,pc-bios/%, $(ROMS))
> >
> > -recurse-all: $(SUBDIR_RULES) $(ROMSUBDIR_RULES)
> > +# Some files are shared between the tools and the emulators.  So  
> > there
> > +# can be a race when the main makefile starts building xyz.o, while
> > +# the recursive make sees a partially built xyz.o and ar(1) fails.
> > +recurse-all: $(SUBDIR_RULES) $(ROMSUBDIR_RULES) | $(TOOLS)
> >
> > #######################################################################
> > # QObject
>
> I still don't understand why that is needed :( (make mysteries).
>
> All shared stuff between $(TOOLS) and $(SUBDIR_RULES) are made from  
> the
> same Makefile invocation.  I don't see where the recursive make can
> build a file that is also built by the normal Makefile.

Think of my porposed Makefile patch!

> And if we have one file that is build in both places, that is the bug
> that we have to fix.
>
> Notice that cutils.o (from Makefile) is built in the root dir, and
> cutils.o (from Makefile.user) is built into libuser/ directory.
>
> I am confused how one can interfer with the other.
>
> VPATH vs vpath problems?

libuser builds some .o files from .c files in $(SRC_PATH). They end up  
in libuser. For those that were built already in .., the .o files are  
taken from there instead.

Andreas

> Later, Juan.