Re: stabs at function entry point?

[Daniel Jacobowitz <drow at mvista dot com>]

On Thu, Mar 14, 2002 at 01:09:43AM +0000, John Levon wrote:
> On Wed, Mar 13, 2002 at 04:25:48PM -0800, Jim Ingham wrote:
> 
> > So my contention was that no one who is doing source level debugging 
> > ever wants to break at the beginning of the prologue.  All sorts of 
> > oddities happen then (the stack is wrong, the current frame is wrong, 
> > etc) which from a source debugging point of view are hard to understand.
> > 
> > When Dale and I first discussed this, he suggested that gdb just throw 
> > away the first source line stab for each function it encounters.  But if 
> > gdb has to throw it away each time to get the debugging experience 
> > right, then that seems a pretty strong argument in itself that the 
> > compiler should not be emitting them...
> 
> Sorry to harp on, but these entries are NOT only useful for gdb. The
> frame + stack problems are irrelevant for users of
> bfd_get_nearest_line() who simply want the global symbol value for
> the function to translate into a reasonable file/line pair.
> 
> A concrete example is my profiler: file/line output for function-based
> summaries should be display the start of the function in the source.
> There is also the lesser problem of hits against the prologue code
> itself - ideally this would also work.
> 
> Please don't focus on what gdb needs at the expense of other users.
> Are there real technical problems with ignoring the first stabs entry ?

Have you looked at the find_nearest_line code for stabs?  It's in
bfd/syms.c.  It reads the line numbers from function stabs into the
line table.  The presence or absence of a matching line number marking
should be No Big Deal for this interface.

-- 
Daniel Jacobowitz                           Carnegie Mellon University
MontaVista Software                         Debian GNU/Linux Developer