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Re: Ada subtypes and base types


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 :-)

jeff
> 
> Andrew.


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