Re: gcc: optimizations, and stack traces

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

Le 09/02/2018 à 13:32, Joerg Sonnenberger a écrit :
> On Fri, Feb 09, 2018 at 11:23:17AM +0100, Maxime Villard wrote:
> > It implies that if a bug occurs _before_ these two instructions are executed,
> > we have a %rbp that points to the _previous_ function, the one we got called
> > from. And therefore, GDB does not display the current function (where the bug
> > actually happened), but displays its caller.
>
> This analysis is wrong. GDB will first of all look for frame annotation
> data, i.e. .eh_frame or the corresponding .debug_frame. Only if it can't
> find such annotation will it fall back to guessing from the function
> itself. We default to building .eh_frame for all binaries, but I'm not
> completely sure if GCC will create async unwind tables by default.

I'll have to re-check the GDB code, but that the previous function was
displayed and not the current one is the conclusion I came to back then. Will
verify tomorrow.

Maxime