Re: [PATCH] Watchpoints + conditionals problem

[Luis Machado <luisgpm@linux.vnet.ibm.com>]

Thanks Vladimir,

Either way is fine with me. The simple fix or the alternate one.

Anybody has any comments?

Regards,
Luis

On Thu, 2007-11-29 at 11:53 +0300, Vladimir Prus wrote:
> Luis Machado wrote:
> 
> > Hi folks,
> > 
> > There is an unexpected behavior when we use software watchpoints (also
> > hardware in some cases) attached to conditional expressions, such as:
> > "watch x if x == <number>", considering "x" a simple "int" type
> > variable.
> > 
> > When that watchpoint goes out of scope, it's marked for disposal at the
> > next stop as obviously there's no way to evaluate the expression "x"
> > anymore. But GDB is still trying to evaluate the conditional part of the
> > watchpoint, even though "x" is out of scope already. Thus, GDB is
> > failing to find correct frame information and ends up in an internal
> > error.
> 
> I've run into same problem yesterday.
> 
> > I've tracked down this issue and it seems we need to check for the
> > disposition field of the watchpoint whenever we check for the return
> > value of a conditional expression.
> > 
> > Attached is a simple patch of what i have in mind to fix this issue. The
> > testcase can be a simple "Hello world"-like binary with a few variables
> > to watch.
> > 
> > Any other ideas?
> 
> I guess ideally we need to:
> 
> 1. Don't check condition at all if bs->stop is already 0.
> 2. Immediately delete watchpoint, don't bother with del_at_next_stop
> 
> But for now, your approach is probably fine -- can anybody approve it?
> 
> - Volodya
>