Jeffrey A Law writes: > On Thu, 2006-03-30 at 18:39 +0100, Andrew Haley wrote: > > Jeffrey A Law writes: > > > On Wed, 2006-03-29 at 14:28 -0700, Tom Tromey wrote: > > > > > > > On irc today we were discussing handling 'this' in gcj. We can add an > > > > attribute to the argument to mark it as non-null... but strangely > > > > there doesn't seem to be a way to mark other local variables as > > > > known-non-null -- a curious deficiency. > > > It seems to me that for other locals that the non-null property > > > ought to be a property of how those locals are assigned a value. > > > ie, if we're going to be able to derive a non-null for a local we > > > should be able to derive it from the RHS of the assignment(s) to > > > that local. > > > > Right, that's true. The idea is that a great many library functions > > either return a valid object or throw an execption, and we can > > propagate that information to VRP> > > > > > IIRC "this" is actually a parameter and thus there's no assignment > > > we can derive information from. > > > > Mmm, yeah. The point is that we solved the problem for "this", but > > not for other things.
> And I think the way to solve this is to mark those interesting > library functions, then fix VRP so that it's not so eager to ignore > function calls :-) Well, it's not just functionss but also global variables. AFAICS there are three sources of data: args, retvals, and globals. And there are quite a few of these globals we can usefully tag as "known never to be null". Andrew.
