[c/4053] Re: problems debugging gcc

[Daniel Jacobowitz <drow@mvista.com>]

On Tue, Dec 04, 2001 at 08:34:54PM +0000, Neil Booth wrote:
> mike stump wrote:-
> 
> > Yes.  Step through bison.simple a couple hundred times, and you'll
> > discover that most of the time, it spends it's time in about two to
> > four places you care about.  One place, is dispatching to actions.  It
> > can be felt, by noticing the line (at least in bison 1.25):
> 
> Have you noticed that you often get the debugger trying to step to a
> line in bison.simple that is in fact in parse.y, and complaining about
> a line out range?

For the curious, this is the exact same problem as c/4053.

> This happens to me very frequently; I have no idea what causes it.  I
> have a sneaking suspicion that this GCC bug is what the original post
> was about, though I'm not sure.

Well, it isn't in the debug format code; the file information in the
RTL is wrong.  And there's nothing obviously incorrect about the code
in cb_file_change...

Aha, I think I see it.  cb_file_change updates input_filename as it
reads.  Compile the testcase from the PR with a breakpoint on
cb_file_change and a breakpoint on emit_line_note.  If I had to guess,
I'd say that the problem was input_filename describing the state of the
lexer where it used to describe the state of the parser.  In
c_expand_body is the line:
  init_function_start (fndecl, input_filename, DECL_SOURCE_LINE (fndecl));

DECL_SOURCE_LINE is fine.  input_filename isn't.

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