On Friday 07 January 2011, Stefano Lattarini wrote:
> Hello automakers.
> 
> Due to current implementation details, when dealing with Yacc sources, automake
> must know the contents of the `$(AM_YFLAGS)' variable (or similar `$(foo_YFLAGS)'
> variables) *statically and unconditionally* in order to always generate proper
> code.
> 
> This is due to the special handling of the `-d' yacc flag; on this issue, read
> at <http://www.gnu.org/software/automake/manual/html_node/Yacc-and-Lex.html>:
>  ``AM_YFLAGS is usually used to pass the -d option to yacc. Automake knows what
>    this means and will automatically adjust its rules to update and distribute
>    the header file built by 'yacc -d'. ''
> 
> And while automake correctly warns if AM_YFLAGS is conditionally *defined*:
> 
>   $ cat configure.ac
>   AC_INIT(x,0)
>   AM_INIT_AUTOMAKE(foreign)
>   AC_PROG_CC
>   AC_PROG_YACC
>   AC_CONFIG_FILES(Makefile)
>   AM_CONDITIONAL(COND,:)
>   $ aclocal
>   $ cat > Makefile.am <<'END'
>   bin_PROGRAMS = foo bar
>   foo_SOURCES = foo.y
>   bar_SOURCES = bar.y
>   if COND
>   AM_YFLAGS = -d
>   endif
>   END
>   $ automake -a -Werror; echo status=$?
>   Makefile.am:5: automake does not support AM_YFLAGS being defined conditionally
>   status=1
> 
> it erronously doesn't warn if AM_YFLAGS is conditionally *extended*:
> 
>   $ cat configure.ac
>   AC_INIT(x,0)
>   AM_INIT_AUTOMAKE(foreign)
>   AC_PROG_CC
>   AC_PROG_YACC
>   AC_CONFIG_FILES(Makefile)
>   AM_CONDITIONAL(COND,:)
>   $ aclocal
>   $ cat > Makefile.am <<'END'
>   bin_PROGRAMS = foo bar
>   foo_SOURCES = foo.y
>   bar_SOURCES = bar.y
>   AM_YFLAGS =
>   if COND
>   AM_YFLAGS += -d
>   endif
>   END
>   $ automake -a -Werror; echo status=$?
>   status=0
> 
> I think this bug shouldn't be difficult to fix, and I'll attempt a fix
> soonish; but as usual, having it in the bug tracker doesn't hurt IMHO.
> 
> Regards,
>   Stefano
> 
The attached patch should fix the bug.  OK for the temporary branch
'yacc-work', to be merged to master afterwards?

Regards,
  Stefano