[Bug translator/5899] $ptr->member in return probe

[jkenisto at us dot ibm dot com]

------- Additional Comments From jkenisto at us dot ibm dot com  2008-03-11 20:19 -------
(In reply to comment #1)
> I think bug #5634 can solve this issue as below:
> $ptr("struct argument")->member
> 

That feature would be useful in general, but I'm not sure how it solves this
problem.  Are you suggesting something like this?

probe kernel.function("myfunc").return
{
    printf("foo->bar on entry was %d\n", $foo->bar);
    foo2 = $foo
    printf("foo->bar on return was %d\n", foo2("struct foo_struct")->bar);
}

I don't think it would be obvious to the average user that $foo->bar gets
evaluated at function entry, but foo2("struct foo_struct")->bar doesn't.

BTW, I said "If I want entry_value($ptr->member), I can just save that value
during my entry probe."  That's kind of optimistic.  The problem is, WHERE would
I save that value, so I know it belongs to this particular function instance? 
Yeah, I could create an associative array indexed by task and (say) stack
pointer (in case of recursion), but that's what this feature was created to
avoid.  In any case, that's just more evidence that we need to get this feature
right.

-- 


http://sourceware.org/bugzilla/show_bug.cgi?id=5899

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