Re: problem debugging assembler functions

[Vladimir Prus <ghost@cs.msu.su>]

On Tuesday 14 June 2005 18:36, Daniel Jacobowitz wrote:
> On Tue, Jun 14, 2005 at 01:21:53PM +0400, Vladimir Prus wrote:
> > Line 2285:
> >
> >  if (frame_id_eq (frame_unwind_id (get_current_frame ()), step_frame_id))
> >  {
> >      ......
> >  }
>
> FYI, this bit...
>
> > Line 2428:
> >
> >  if (step_over_calls == STEP_OVER_UNDEBUGGABLE
> >       && ecs->stop_func_name == NULL)
> >   {
> >        /* The inferior just stepped into, or returned to, an
> >          undebuggable function (where there is no symbol, not even a
> >          minimal symbol, corresponding to the address where the
> >          inferior stopped).
> >         */
> >
> >         ........
> >
> >         insert_step_resume_breakpoint_at_frame (
> >              get_prev_frame (get_current_frame ()));
> >   }
>
> is somewhat newer than this bit.
>
> > The condition is the second code block is taken and breakpoint is indeed
> > set. I have two questions:
> >
> > 1. Is "just stepped into ... function" comment accurate? I think that all
> > cases of steppin into function are handled by the previous
> >
> >  if (frame_id_eq (frame_unwind_id (get_current_frame ()), step_frame_id))
> > {}
> >
> > condition, and all code paths inside that condition end with return. So,
> > the second code block is not executed when we've just stepped into a
> > function. Is the code intended to handle only the case when we've
> > *returned* to undebuggable function?
>
> It was intended to handle both.  Nowadays, there's a good chance it has
> handled only the latter.

Ok.

> > 2. In my case, no function names for assembler modules are present in
> > debug info, but line information is there, so the function is debuggable.
> > Is there a way to check of line info in condition, not for function name?
>
> You have line numbers, but not even minimal symbols?  That is, ELF
> symbols, not DWARF2 symbols.  

Exactly. ELF symbol table is absolutely empty. 

> That's really bizarre.  

Well, for a binary for embedded system with no dynamic linking this is not so
unreasonable. Anyway, that's not something I can easily change.

> We don't have a  
> good interface for handling functions with line numbers but no sym or
> minsym, but perhaps we need one.  I agree that the presence of line
> number information seems more relevant right here.

FWIW, I've just modified that code to be:

  ecs->sal = find_pc_line (stop_pc, 0);
  .......
  if (step_over_calls == STEP_OVER_UNDEBUGGABLE
      && ecs->sal.line == 0)

and it works as expected. Does the change seem reasonable?

- Volodya