[DVDnav-discuss] parallel make problem

[Dan Nicholson]

On Sat, Aug 30, 2008 at 9:27 AM, Dan Nicholson <dbn.lists at gmail.com> wrote:
> On Sat, Aug 30, 2008 at 9:24 AM, Dominik 'Rathann' Mierzejewski
> <dominik at greysector.net> wrote:
>> On Saturday, 30 August 2008 at 17:30, Dan Nicholson wrote:
>>> On Sat, Aug 30, 2008 at 7:05 AM, Dominik 'Rathann' Mierzejewski
>>> <dominik at greysector.net> wrote:
>>> > I'm experiencing a problem with make -j2:
>> [...]
>>> > But I'd rather have a proper fix instead of workarounds.
>>> > Ideas?
>>>
>>> You really don't want to have a target dependent on a directory
>>> because make will always think the target is out of date.
>>
>> Yeah, I thought there was something fundamentally wrong here.
>>
>>> That prevents doing the right thing:
>>>
>>> $(OBJS) $(DVDREAD_OBJS) $(SHOBJS) $(DVDREAD_SHOBJS): $(.OBJDIR)
>>>
>>> I think the only way to handle this race free without polluting make's
>>> timestamp handling is to make the targets explicitly handle the mkdir
>>> on their own and get rid of the target for it (watch out for gmail
>>> wrapping):
>>>
>>> diff --git a/Makefile b/Makefile
>>> index cb1340e..ee2df97 100644
>>> --- a/Makefile
>>> +++ b/Makefile
>>> @@ -75,20 +75,19 @@ $(SRCS) $(DVDREAD_SRCS): version.h
>>>
>>>  # General targets
>>>
>>> -$(.OBJDIR):
>>> -       mkdir $(.OBJDIR)
>>> -
>>> -${DVDREAD_LIB}: version.h $(.OBJDIR) $(DVDREAD_OBJS) $(BUILDDEPS)
>>> +${DVDREAD_LIB}: version.h $(DVDREAD_OBJS) $(BUILDDEPS)
>>>         cd $(.OBJDIR) && $(AR) rc $@ $(DVDREAD_OBJS)
>>>         cd $(.OBJDIR) && $(RANLIB) $@
>>>
>>> -${DVDREAD_SHLIB}: version.h $(.OBJDIR) $(DVDREAD_SHOBJS) $(BUILDDEPS)
>>> +${DVDREAD_SHLIB}: version.h $(DVDREAD_SHOBJS) $(BUILDDEPS)
>>>         cd $(.OBJDIR) && $(CC) $(SHLDFLAGS) $(LDFLAGS) -ldl -Wl,-soname=$(DVDREA
>>>
>>>  .c.so: $(BUILDDEPS)
>>> +       @[ -d $(.OBJDIR) ] || mkdir -p $(.OBJDIR)
>>>         cd $(.OBJDIR) && $(CC) -fPIC -DPIC -MD $(CFLAGS) -c -o $@ $<
>>>
>>>  .c.o:  $(BUILDDEPS)
>>> +       @[ -d $(.OBJDIR) ] || mkdir -p $(.OBJDIR)
>>>         cd $(.OBJDIR) && $(CC) -MD $(CFLAGS) -c -o $@ $<
>>>
>>>
>>> @@ -133,7 +132,8 @@ distclean: clean
>>>         find . -name "*~" | xargs rm -rf
>>>         rm -rf config.mak
>>>
>>> -dvdread-config: $(.OBJDIR)
>>> +dvdread-config:
>>> +       @[ -d $(.OBJDIR) ] || mkdir -p $(.OBJDIR)
>>>         @echo '#!/bin/sh' > $(.OBJDIR)/dvdread-config
>>>         @echo 'prefix='$(PREFIX) >> $(.OBJDIR)/dvdread-config
>>>         @echo 'libdir='$(shlibdir) >> $(.OBJDIR)/dvdread-config
>>
>> This is very ugly IMHO. How about sneaking mkdir obj into version.sh rule?
>
> That should work as long as we're sure all the objects are dependent
> on version.h (I think we are).

Except dvdread-config isn't, so that either needs to depend on
version.h, or it needs the commands. `make dvdread-config' is
perfectly legal and would fail if run immediately after configure2
from a fresh checkout.

--
Dan