Re: breakpoint for accessing memory location

Rodney M. Bates
2006-10-21T15:06:10Z

Eli Zaretskii wrote:
> The beginning of that section has a better explanation:
>
> You can use a watchpoint to stop execution whenever the value of an
> expression changes, without having to predict a particular place where
> this may happen.
>
> What text would you suggest to have there that would have helped you
> recognize that this is the feature you wanted? If you were looking
> for some specific words or phrases, please tell what they are. This
> will allow us to improve the manual.
>
> TIA
>

I have never had trouble understanding this sentence, although I have
thought "a particular place in the code" would be even clearer.

But while this subject is open, I would like to see more explanation on just
what the semantics of evaluating a watchpoint expression are. An expression
always is evaluated in a particular context that can affect the legality/result,
but in the case of a watchpoint, execution is proceeding and changing the
context. I have never been sure what the rules are.

For example, I sometimes want to watch p->f, where p is local variable that
I know perfectly well will soon cease to exist, but I also know *p will
remain. I've long since learned that watching p->f doesn't work. Instead,
I print the address of p->f and then watch the contents of that address.

But more information on the general rules would be helpful in the manual.

--
-------------------------------------------------------------
Rodney M. Bates, retired assistant professor
Dept. of Computer Science, Wichita State University
Wichita, KS 67260-0083
316-978-3922
rodney.bates@wichita.edu