Re: cvs commit: src/gnu/usr.bin/gdb/gdb

["Simon 'corecode' Schubert" <corecode@xxxxxxxxxxxx>]

On 18.11.2004, at 04:42, YONETANI Tomokazu wrote:
> > >  Modified files:
> > >    gnu/usr.bin/gdb/gdb  Makefile
> > >  Log:
> > >  Use the YACC source for c-exp.y and f-exp.y, not the pre-built
> > >  BISON parse. This solves the *very* strange build problem with
> > >  -jX in buildworld, where make tries to build this files from
> > >  source using the default rules. Those rules are not save for
> > >  parallel builds.
> > Thanks. Although I'd really like to know why these *explicit* sources
> > (.c) get updated from the *implicit* (.y) sources...
> When the tree is checked out, *.c files get updated earlier than *.y 
> files,
> making the latter slightly newer than the former.

Ah. Now I think I know why this is happening. the .c files are never 
used as explicit sources, but only as implicit and thus get updated 
from the .y files (am I wrong here?)
> See the difference? That is, when [cf]-exp.c but not [cf]-exp.y are
> specified in SRCS, suffix rule .y.c from sys.mk is used, which is not
> -j safe (already pointed out by Brad Harvell on bugs@), because 
> multiple
> instances of ${YACC} try to write to the same y.tab.c file(and probably
> unlink it before writing to it). When [cf]-exp.y are specified in SRCS 
> on the
> other hand, the `.for _YSRC' rule in bsd.dep.mk produces explicit 
> rules for
> each *.y file using `${YACC} ${YFLAGS} -o'.

For what amazing reason does bsd.dep.mk handle .y and .l files 
explicitly, and doesn't rely on the implicit rules?

> To summarize, if SRCS contains more than one *.c file having 
> corresonding
> newer *.y files in the same directory, `make -jN depend' may fail 
> depending
> on the mtime of *.c and *.y. As of gnu/usr.bin/gdb/Makefile rev 1.5, 
> scm-exp.c
> is the only *.c that has corresponding *.y in the same directory(which 
> is
> slightly newer because of the order of cvs checkout).
> The question is, whether we can change .y.c rule in sys.mk to make it 
> -jN
> (as pointed out by Brad).

Sure, I'd say. Well, okay, it will break behaviour wrt y.tab.h, but I 
think this needs to be done. Maybe we can add the non-deterministic 
behaviour back by mv ${.IMPSRC:S/.y/.h} y.tab.h [hack alert!]

cheers
  simon

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