GDB Stacktrace for optimized code!

GDB Stacktrace for optimized code!

[Thamil K]

Hi Geeks,

For programs compiled with -O2, where the compiler uses 'jmp' where
possible instead of 'call' or where callee doesn't push $rbp onto the
stack, gdb is still able to generate stack trace properly.  But by
inspecting the $rbp and return address, I am unable to trace back the
calls. I would like to know how gdb synthesises the stack trace ?  Any
pointers on documentation?   Thanks in advance.

Thanks
Thamil

Re: GDB Stacktrace for optimized code!

[Hannes Domani]

 Am Dienstag, 20. April 2021, 07:55:39 MESZ hat Thamil K via Gdb <gdb@sourceware.org> Folgendes geschrieben:

> Hi Geeks,
>
> For programs compiled with -O2, where the compiler uses 'jmp' where
> possible instead of 'call' or where callee doesn't push $rbp onto the
> stack, gdb is still able to generate stack trace properly.  But by
> inspecting the $rbp and return address, I am unable to trace back the
> calls. I would like to know how gdb synthesises the stack trace ?  Any
> pointers on documentation?  Thanks in advance.

For tail call optimization ('call' optimized to 'jmp'), see [1].
For for frame pointer omission ($rbp) I couldn't find documentation in gdb, but this blog [2] has some explanations.

[1] https://sourceware.org/gdb/download/onlinedocs/gdb/Tail-Call-Frames.html
[2] https://yosefk.com/blog/getting-the-call-stack-without-a-frame-pointer.html


Hannes