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Date: Thu, 30 Dec 2004 19:36:00 -0000
From: "H. J. Lu" <hjl@lucon.org>
To: gcc@gcc.gnu.org, GDB <gdb@sources.redhat.com>
Subject: Re: GDB 6.3 assumes that DW_AT_frame_base exists
Message-ID: <20041230193618.GA16661@lucon.org>
References: <20041222011627.GA15293@lucon.org> <41C9577D.3010509@redhat.com> <20041222182449.GA29407@lucon.org> <20041223034318.GA19580@nevyn.them.org> <20041230192424.GA16440@lucon.org>
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On Thu, Dec 30, 2004 at 11:24:24AM -0800, H. J. Lu wrote:
> On Wed, Dec 22, 2004 at 10:43:19PM -0500, Daniel Jacobowitz wrote:
> > On Wed, Dec 22, 2004 at 10:24:49AM -0800, H. J. Lu wrote:
> > > > GDB not being able to debug GCC is a GDB problem.  (Or possibly a 
> > > > problem of the compiler than was used to compile the GCC being 
> > > > debugged).  Either way I am pretty sure that readelf is blameless in 
> > > > this situation.
> > > 
> > > I think gcc may be correct and gdb just can't handle location list
> > > correctly.
> > 
> > If you believe there is a GDB bug, please submit a bug report with
> > self-contained test case.
> 
> I don't know if it is a gcc or gdb bug, and I don't have a
> self-contained testcase. The only thing I see is gdb crushes on
> cc1 from gcc 4.0. It seems that gdb 6.3 assumes DW_AT_frame_base
> exists for a function. But not all functions in cc1 in gcc 4.0
> have DW_AT_frame_base and gdb 6.3 crushes in dwarf_expr_frame_base.

I think it is a gdb 6.3 bug since idb has no problem. When evaluating
a location list, gdb does

	...
	ctx->get_frame_base = dwarf_expr_frame_base;
	...

dwarf_expr_frame_base uses DW_AT_frame_base to get frame base. Since
DW_AT_frame_base doesn't exist for tls_symbolic_operand, gdb crushes.


H.J.