Le 28 juin 06 à 20:07, Paul Eggert a écrit :
"Joel E. Denny" <[EMAIL PROTECTED]> writes:
Why was the ability to concatenate several %union's together added?
I'm the guilty party on that. As I recall, the problem was that Bison
formerly had undefined behavior if you had multiple %unions (it
generated garbage code), and I wanted it to do something more
reasonable. I didn't put a lot of thought into it, and I don't think
anybody's really relying on it. We shouldn't let this tail wag any
dog.
:) I think I understand the meaning, but that's the first time I
parse this saying (in French sayings are said to be "expressions"
(yep, same word as in English). Parsing an expression reads even
better).
Now that I think of it, "%union foo { ... } %union bar { ... }"
probably generates garbage code even now.
No it does not: it gives the priority to the latest. Just as
%define still does. That's simply a matter of having muscle_define
catch redefinitions once for all.
I guess we should simply
disallow multiple %union, as C does.
Your patch is needed. IMO it was just too soon, because nothing
else is ready, but some day we will need it.
Stepping back from this a bit, I'm totally confused now by all the
directives being proposed.
My proposal is based on two directives: %public goes into the header
(and of course %union belongs to %public), and %private does not.
I suggest that %{ ... %} be sugar for %public, Joel thinks %private
is more appropriate.
Here's one idea to simplify things a bit. How about if we say that
"%union { ... }" is treated like:
%{
typedef union { ... } YYSTYPE;
%}
This is the semantics the user must see. What we implement can be
different. And because I'm in favor of (tamed) multiple %union,
I am still in favor of a split %public part *as an implementation
detail*. I am against exposing this split thing to the user, the
order is way enough.
