Subject: Re: [PATCH] yacc, lex: new 'no-ylwrap' option to prevent use of the 'ylwrap' script

From: Stefano Lattarini <[email-masked]>
Date: Tue, 26 Jun 2012 18:57:49 +0200

Hi Eric.

On 06/26/2012 06:27 PM, Akim Demaille wrote:
>
> Le 26 juin 2012 à 18:18, Eric Blake a écrit :
> 
>> Just from reading this summary, the idea of improving AC_PROG_LEX and
>> AC_PROG_YACC to be more useful makes sense, especially if it would make
>> automake easier to maintain.  What sort of improvements are needed?
> 
> In the present case, I believe the only thing Automake needs
> to know is whether -o is supported by lex/yacc.
>
Yes.  And to ensure proper compatibility with C++ and with the use of the
'-d' option, we should consider the '-o' support good enough only provided
that, when "yacc -d -o foo.C-EXT" is used, the name of the created header
is "foo.H-EXT", where H-EXT is C-EXT with all 'c' characters substituted
by 'h' ones (so that foo.c -> foo.h, foo.c++ -> foo.h++, foo.cc -> foo.hh,
etc).  This is what Bison does.

Once we know that lex supports '-o', the determination of the value of
$LEX_OUTPUT_ROOT will mostly become moot, and could be dispensed with
(at least for what concerns Automake).

Also, it would be nice if AC_PROG_YACC and AC_PROG_LEX would allow us to
change the list of the searched programs (this will allow the Automake
configure script to prefer non-bison 'yacc' and non-flex 'lex' programs
for use in the testsuite, to ensure better coverage).

Finally, while we are at it, we might also think about making default
values for $YACC and $LEX configurable (rather than hard-coding them
to resp. 'yacc' and ':').

Oh, and setting a couple of (self-explanatory) variables $LEX_IS_FLEX
and $YACC_IS_BISON wouldn't hurt (albeit it would not be needed by
Automake at this point).

Regards,
  Stefano