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Re: [RFC] Is skip_prologue_using_sal actually usable?
On Tue, Nov 09, 2004 at 02:53:20PM +0100, Mark Kettenis wrote:
> Date: Mon, 8 Nov 2004 21:43:14 -0500
> From: Daniel Jacobowitz <drow@false.org>
>
> If you want the first instruction that is not part of the prologue,
> then you have no more reason to skip prologues at all. My
> understanding is that prologue skipping accomplishes two things:
>
> B? - Get the arguments into their save slots so that we can find
> and display them.
>
> A? - Get the frame pointer into a sane state so we can backtrace.
>
> Well, we've taken care of (A) already - the new frame code requires
> being able to backtrace from the first instruction of a function,
> and we do it. (I think we fall down more often in the epilogue than we
> do in the prologue now.)
>
> Assuming the second point is (A) and the first one is (B):
Oops -) Yes, that's what I meant.
> Although it sounds plausible I think it's something we should revisit
> when GDB actually supports "locations" properly.
>
> In the mean time, we really should strive for some consistency in
> where we put function breakpoints. What do you think about my
> statement that too early is better than to late?
I don't think I agree. We used to have a lot of problems with placing
breakpoints after branches; that, obviously, is too late (excepting the
PIC register setup). But I find the inaccuracy of displayed function
arguments to be my single biggest day-to-day problem in using GDB.
Just moments ago I wasted a couple minutes discovering that a pointer
hadn't been saved to the stack yet.
--
Daniel Jacobowitz