Jan Harkes <jaharkes_at_cs.cmu.edu> writes:

> The test for success was added to avoid build problems later on when
> people didn't have bison or yacc installed. The warnings were pretty
> obscure. In fact I think the missing script basically creates an empty
> rp2gen_parser.c, which then results in a lot of obscure warnings during
> the link phase that don't really indicate that the 'generated' parser
> code is really an empty file.
>
> So if AC_PROG_YACC does the right thing already, but only fails to set
> the ac_cv_prog_YACC variable when /usr/bin/yacc is installed, then I'm
> just testing the wrong variable.

It doesn't do the right thing.  It looks for bison and byacc, and if
found sets YACC to those and ac_cv_prog_YACC.  If not found, it sets
YACC to yacc - without checking that a yacc is there - and doesn't set
ac_cv_prog_YACC.  This is clearly from the days when of course all
computers had yacc, since it was in Sixth Edition or some such, so how
could you have a machine without it.  My AC_CHECK_PROGS looks for yacc
explicitly, so it will behave differently in 'use yacc by default' and
'found yacc' cases.