Re: [RFC] fix for avr_skip_prologue()

[Andrew Cagney <ac131313@ges.redhat.com>]

> Hi,
> 
> Before I commit this, I wanted to know if this is the correct fix or just
> an evil hack side-stepping the some other problem.
> 
> The problem shows up when I set a break point on a simple function as
> such:
> 
>   (gdb) b foo_simple
> 
> If foo_simple() has no prologue, the break point is set at the _end_ of
> the function (effectively the return insn).
> 
> If this fix is acceptable, is it too late to make it into the 5.2 branch?

I don't think your change is any worse than many other *_skip_prologue() 
tweaks.  A typical skip_prologue() function is an accumulation of 
heuristics and a lot of comments.

> 2002-07-19  Theodore A. Roth  <troth@verinet.com>
> 
> 	* gdb/avr-tdep.c(avr_skip_prologue): Fix to return the correct pc.
> 
> Index: gdb/avr-tdep.c
> ===================================================================
> RCS file: /cvs/src/src/gdb/avr-tdep.c,v
> retrieving revision 1.4
> diff -u -p -r1.4 avr-tdep.c
> --- gdb/avr-tdep.c	17 Jun 2002 23:32:27 -0000	1.4
> +++ gdb/avr-tdep.c	19 Jul 2002 18:33:30 -0000
> @@ -995,7 +995,12 @@ avr_skip_prologue (CORE_ADDR pc)
>      {
>        sal = find_pc_line (func_addr, 0);
> 
> -      if (sal.line != 0 && sal.end < func_end)
> +      /* troth/2002-70-19: For some very simple functions, gcc doesn't
> +         generate a prologue and the sal.end ends up being the insn (2 bytes)
> +         before func_end (the address of the next func). By adjusting
> +         func_end, we can catch these functions and return the correct pc. */

I'd just also mention that the instruction in question is ``return'' and 
is two bytes long.

> +      if (sal.line != 0 && sal.end < (func_end-2))
>  	return sal.end;
>      }

enjoy,
Andrew

>