Joel E. Denny wrote: > On Sat, 22 Oct 2005, Frank Heckenbach wrote: > > > Joel E. Denny wrote: > > > >> On Fri, 21 Oct 2005, Frank Heckenbach wrote: > >> > >>> Akim Demaille wrote: > >>> > >>>> Maybe that does not deserve that much attention: it seems pretty weird > >>>> not to use a value. A warning seems a better feature. > >>> > >>> I sometimes attach some kinds of flags (integer type) to some > >>> symbols that I need in some, but not all, rules that use that > >>> symbol. So, if you go for the warning, could you please make it > >>> optional? (I think it would be a useful feature in general, > >>> including several of my grammars, but in some cases I'd probably > >>> prefer to turn it off.) > >> > >> If your semantic value is just an integer, then you probably won't declare > >> a destructor. In that case, I should think there's no reason for bison to > >> generate a warning. Would that resolve your issue? > > > > That would probably work. However, I'm considering whether such a > > warning might not be useful even in absence of destructors in many > > cases (not the above-mentioned grammar, of course, but many others), > > as not using a semantic value is often, as Akim said, pretty weird. > > I can't really tell off-hand. I guess I'd have to check the effects > > of such a warning on my grammars (which usually don't have > > destructors, yet), but I suppose it would be useful in a number of > > cases. > > Yeah, I think I agree. However, instead of a global switch, I still argue > that something like YYUSE($5); in the semantic actions would be cleaner. > That way, when looking at a semantic action, you'd be able to tell exactly > which semantic values were intentionally not used. Of course, for old > grammars, going back and adding these might be a bit of work...
Yes. And it wouldn't be backward-compatible with older Bison versions that don't have YYUSE. I guess one could #ifdef around it. OTOH, making the warning optional shouldn't take more than a global flag in Bison unless I'm missing something. (Newly written code without backward-compatibility concerns could, and perhaps should, still use YYUSE then, of course.) Frank -- Frank Heckenbach, [EMAIL PROTECTED] http://fjf.gnu.de/ GnuPG and PGP keys: http://fjf.gnu.de/plan (7977168E) _______________________________________________ Help-bison@gnu.org http://lists.gnu.org/mailman/listinfo/help-bison