Re: [rfa/6.0] Fix a thinko in dwarf2loc

Elena Zannoni
2003-09-09T22:45:18Z

Daniel Jacobowitz writes:
> On Tue, Sep 09, 2003 at 05:27:10PM -0400, Elena Zannoni wrote:
> > Daniel Jacobowitz writes:
> > > On Sun, Aug 24, 2003 at 12:48:55PM -0400, Daniel Jacobowitz wrote:
> > > > On Sun, Aug 17, 2003 at 04:58:22PM -0400, Daniel Jacobowitz wrote:
> > > > > On Fri, Aug 01, 2003 at 03:32:45PM -0400, Daniel Jacobowitz wrote:
> > > > > > Any variable with DW_OP_reg* requires a frame to read it - what
> > > > > > symbol_read_needs_frame () really means is "is this variable meaningful when
> > > > > > the program is not running".
> > > > > >
> > > > > > This would show up in the testsuite, but GCC doesn't tend to put locals in
> > > > > > registers without optimization or register keywords everywhere. Symptom is
> > > > > > that a watchpoint was not deleted when we left its scope, since we thought
> > > > > > it was global.
> > > > > >
> > > > > > OK?
> > > > >
> > > > > Ping...
> > > > >
> > > > > [Does dwarf2loc fall under the maintenance umbrella of the dwarf2
> > > > > reader?]
> > > >
> > > > Ping? I would like to fix this bug for 6.0.
> > >
> > > Jim, Elena? I hit this bug again in testing the
> > > deprecated_safe_get_selected_frame () patch.
> > >
> > > > > > 2003-08-01 Daniel Jacobowitz <drow@mvista.com>
> > > > > >
> > > > > > * dwarf2loc.c (dwarf2_loc_desc_needs_frame): Variables in a
> > > > > > register do need a frame.
> > > > > >
> > > > > > --- gdb-5.3.20030801/gdb/dwarf2loc.c.orig 2003-08-01 14:58:57.000000000 -0400
> > > > > > +++ gdb-5.3.20030801/gdb/dwarf2loc.c 2003-08-01 15:00:05.000000000 -0400
> > > > > > @@ -318,7 +318,7 @@ dwarf2_loc_desc_needs_frame (unsigned ch
> > > > > >
> > > > > > free_dwarf_expr_context (ctx);
> > > > > >
> > > > > > - return baton.needs_frame;
> > > > > > + return baton.needs_frame || ctx->in_reg;
> > > > > > }
> > > > > >
> >
> > Hmmm, the ctx just got freed, you cannot dereference it. Need to use a
>
> Eek, I'm embarassed. You are so right.
>
> > local variable. What you are really saying here is that the
> > needs_frame variable is not sufficient to describe what's needed. Can
> > the case be added, so that needs_frame becomes OK? Proabably you
> > need another need_frame_* function.
>
> No, I can't. The needs_frame_* functions are hooks for things which
> are external to the expression evaluator - concepts like "object" and
> "thread local storage address" which require information. But the
> evaluator won't actually try to read from the register when parsing a
> DW_OP_reg1; it just sets in_reg.

Oh, ok, I guess save ctx->in_reg in a local variable then.

elena

>
> --
> Daniel Jacobowitz
> MontaVista Software Debian GNU/Linux Developer