GDB 5.2/5.3 breakpoint bug

Daniel Jacobowitz drow@mvista.com
Mon Jan 13 22:00:00 GMT 2003


On Wed, Jan 08, 2003 at 10:40:02PM -0500, Daniel Jacobowitz wrote:
> On Wed, Jan 08, 2003 at 02:45:23PM -0800, Ching Lai wrote:
> > Hi Daniel,
> > 
> > > > Comment out the line 2753 in gdb 5.21 and 2777 in gdb  5.3 and build
> > them
> > > on
> > > > solaris seems to work OK with two test cases.
> > > >
> > > > Now the  question is to figure out why this line is added in gdb 5.21
> > and
> > > > gdb 5.3?
> > >
> > > The line is supposed to be there; it's so we know what is and isn't
> > > inside a function.  You need to explain better why it's causing a
> > > problem in find_pc_sect_line.
> > 
> > The problem is the linetable in different symbol tables have the
> > same pc address in my testcase. One has valid number and the other one
> > with line number as 0 (which is added by the extra record_line()).
> > 
> > In gdb 5.2.1 release of find_pc_set_line in symtab.c file.
> > 
> >   1788        /* Is this file's best line closer than the best in the other
> > files?
> >   1789           If so, record this file, and its best line, as best so far.
> > */
> >   1790
> >   1791        if (prev && (!best || prev->pc > best->pc))
> >   1792          {
> >   1793            best = prev;
> >   1794            best_symtab = s;
> >   1795
> >   1796            /* Discard BEST_END if it's before the PC of the current
> > BEST.  */
> >   1797            if (best_end <= best->pc)
> >   1798              best_end = 0;
> >   1799          }
> > 
> > Since the line 1791 prev->pc with valid line number is not greater than
> > best->pc
> > which has 0 as line number, so it did not pick up the correct symbol file.
> > 
> > If the record_line is need in gdb 5.2.1 and gdb 5.3, then the line 1791
> > might
> > need an extra condition to void picking up the wrong symbol table which has
> > line
> > number as 0 as added by record_line().
> > 
> > 1791        if (prev && (!best || prev->pc > best->pc) && (prev->line != 0))
> > 
> > 
> > Here are the debugging  section of my observation.
> 
> Thanks for the extra detail.  I see what's going on now; I believe this
> patch should also avoid the problem.  Does it?

Ching Lai reported that this patch solved the problem, and I'm checking
it in.  This fixes PR gdb/849.

> 2002-03-08  Daniel Jacobowitz  <drow@mvista.com>
> 
> 	* symtab.c (find_pc_sect_line): Don't consider end-of-function
> 	lines.
> 
> Index: symtab.c
> ===================================================================
> RCS file: /cvs/src/src/gdb/symtab.c,v
> retrieving revision 1.84
> diff -u -p -r1.84 symtab.c
> --- symtab.c	2 Jan 2003 14:27:26 -0000	1.84
> +++ symtab.c	9 Jan 2003 03:38:36 -0000
> @@ -2012,9 +2012,11 @@ find_pc_sect_line (CORE_ADDR pc, struct 
>           the first line, prev will not be set.  */
>  
>        /* Is this file's best line closer than the best in the other files?
> -         If so, record this file, and its best line, as best so far.  */
> +         If so, record this file, and its best line, as best so far.  Don't
> +         save prev if it represents the end of a function (i.e. line number
> +         0) instead of a real line.  */
>  
> -      if (prev && (!best || prev->pc > best->pc))
> +      if (prev && prev->line && (!best || prev->pc > best->pc))
>  	{
>  	  best = prev;
>  	  best_symtab = s;
> 

-- 
Daniel Jacobowitz
MontaVista Software                         Debian GNU/Linux Developer



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