Re: patch to fix bad interaction between Bison 1.75b and flex

[Paul Eggert]

> Cc: address@hidden, address@hidden
> From: Akim Demaille <address@hidden>
> Date: Sun, 05 Jan 2003 14:26:40 +0100
> User-Agent: Gnus/5.090008 (Oort Gnus v0.08) Emacs/21.2 (i386-pc-linux-gnu)
> 
> 
> | I installed the following patch.
> | 2002-12-13  Paul Eggert  <address@hidden>
> | 
> |     Fix a bad interaction with flex 2.5.23 reported by Bruce Lilly in
> |     <http://mail.gnu.org/pipermail/bug-bison/2002-November/001929.html>.
> |     * data/yacc.c (YYLTYPE, struct yyltype): Do not define unless
> |     locations are requested.
> |     (union yyalloc): Do not depend on YYLTYPE_IS_TRIVIAL unless
> |     locations are requested.
> 
> I don't understand how a Bison symbol, completely unknown to the
> scanner (such as yylval or yylloc) can interact here.

Sorry, I don't follow.  YYLTYPE is known to the scanner, because the
scanner includes y.tab.h or equivalent.  If locations are not
requested but the scanner wants to use the name "YYLTYPE" for
something else, then unnecessary problems ensue.