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Re: problem debugging assembler functions
On Tuesday 14 June 2005 18:58, Daniel Jacobowitz wrote:
> On Tue, Jun 14, 2005 at 06:54:03PM +0400, Vladimir Prus wrote:
> > > > 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.
>
> Not having dynamic symbols, sure, that's perfectly reasonable. Those
> go into target memory. But this is far from the only thing in GDB that
> is not going to work without a static symbol table! For instance, you
> can't use prologue analysis. You'll never find the start of any
> function.
Do you mean prologue analysis for assembler modules? For C++ modules DWARF2
info contains everything.
Well, I don't need to analyse prologue for assembler modules at all, because
if I understand correctly it's only needed to proper unwind stack, and I have
a much better way for stack unwinding. My target is actually a simulator, so
I just store register values on each call instruction and can fetch them via
extended version of "get registers" remote protocol command.
> > > 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?
>
> I'm not thrilled with adding another lookup here; this code executes
> quite a few times when stepping.
The current code looks like:
if (step_over_calls == STEP_OVER_UNDEBUGGABLE
&& ecs->stop_func_name == NULL
{
}
if (step_range_end == 1)
{
/* It is stepi or nexti.
...
return;
}
ecs->sal = find_pc_line(stop_pc, 0)
So, moving 'find_pc_line' above will reasult in extra lookup only if
- the command is stepi/nexti, or
- the first condition evaluates to true (which means we've entered
undebuggable code)
I have no idea is that's bad or not performance-wise, just clarifying what's
going on.
> It does seem plausible, but it would
> need wider testing.
Ok.
- Volodya