Re: gcc: optimizations, and stack traces

[Maxime Villard <max%m00nbsd.net@localhost>]

Le 09/02/2018 à 12:13, Valery Ushakov a écrit :
> [Summoning Krister]
>
> On Fri, Feb 09, 2018 at 11:23:17 +0100, Maxime Villard wrote:
>
> > There are also several cases where functions in the call tree can disappear
> > from the backtrace. In the following call tree:
> >
> > 	A -> B -> C -> D   (and D panics)
> >
> > if, in B, GCC put the two instructions after the instruction that calls C,
> > the backtrace will be:
> >
> > 	A -> C -> D
> >
> > This can make a bug completely undebuggable.
>
> Does gcc actually generates code like that?  I thought that it can
> delay frame pointer creation, but only until it needs to make a nested
> call, to C in your example, (as in the sample I showed in another mail
> to this thread).

Mmh, now I'm not so sure about this. Wait a minute, I'll re-give a look and
try to understand what I was doing.

Maxime