https://gcc.gnu.org/bugzilla/show_bug.cgi?id=38534
--- Comment #33 from Lukas Grätz <lukas.gra...@tu-darmstadt.de> ---
(In reply to Jakub Jelinek from comment #32)
> (In reply to Lukas Grätz from comment #31)
> > Even when I compile a simple program with gcc -O2 -g:
> >
> > #include <stdlib.h>
> > int main(int argc, char** argv) {
> > abort();
> > }
> >
> >
> > I still get an "argc=<optimised out>":
>
> Sure, debugging info in optimized code is best effort.
>
> > Yes, for a better debugging, it would be nice if optimised code would just
> > not be optimised... But this goes against optimization.
>
> The significant difference between other optimizations and this one is
> that normal optimizations affect the debuggability of the optimized function.
> This one affects the debuggability of all callers as well, even if they are
> compiled in a way that should make them more debuggable.
> Normally, if debugging optimized code doesn't work out, one can simply
> rebuild that code with -O0 or -Og to make it more debuggable.
> Here one would also need to rebuild all the shared libraries it uses.
When the debugger is inside the debuggable -O0 or -Og compiled function, we
would see all parameters and current variable values. However, in the bt
example, we are in another function. So the parameters are only available at
best effort.
I just noticed that for my simple.c example above, I get "argc=<optimised out>"
even with -Og. However, when breakpoint is somewhere else,
(gdb) break main
(gdb) run
(gdb) bt
I get the correct "argc=1". The same applies to your example with "break baz".
It is just not guaranteed that gdb is able to reconstruct function parameters
when we are in some other function.
