target/6522: Incorrect struct offset for unaligned 64-bit fields in debug information

[Daniel Jacobowitz]

On Fri, May 03, 2002 at 06:20:33AM -0400, Jakub Jelinek wrote:
> On Thu, May 02, 2002 at 09:32:08PM -0400, Daniel Jacobowitz wrote:
> > On Tue, Apr 30, 2002 at 11:30:38PM -0000, jakub@gcc.gnu.org wrote:
> > > Synopsis: Incorrect struct offset for unaligned 64-bit fields in debug information
> > > 
> > > State-Changed-From-To: open->feedback
> > > State-Changed-By: jakub
> > > State-Changed-When: Tue Apr 30 16:30:37 2002
> > > State-Changed-Why:
> > >     You have not provided t64.cpp (or better t64.ii if t64.cpp
> > >     includes some headers).
> > > 
> > > http://gcc.gnu.org/cgi-bin/gnatsweb.pl?cmd=view%20audit-trail&database=gcc&pr=6522
> > 
> > I can confirm this in 3.1.  It's present in 3.0, but worked in 2.95.3. 
> > It's quite annoying, since GDB can't infer the right answer.
> 
> Reproduced, looking into it.

Thanks!

> > Here's another example:
> > 
> > typedef __complex__ float cf;
> > struct x { char c; cf f; } __attribute__ ((__packed__));
> > struct unpacked_x { char c; cf f; };
> > 
> > Compile and compare the debug info; it does not respect __packed__.
> 
> This testcase has wrong debug info in 2.95.3 and
> 2.96-RH, but looks correct in 3.0 and 3.1:
>         .ascii "f\0"    # DW_AT_name
>         .byte   0x1     # DW_AT_decl_file
>         .byte   0x2     # DW_AT_decl_line
>         .long   0x4f    # DW_AT_type
>         .byte   0x2     # DW_AT_data_member_location
>         .byte   0x23    # DW_OP_plus_uconst
>         .uleb128 0x1
> ^^^^^^^^^^^^^^^^^^^^
> (this used to be 0x4 with older gcc's).

Oh, you're right.  It fails in 3.0 with stabs information, which I
reported to this list earlier and no one's had time to fix
(http://gcc.gnu.org/ml/gcc-bugs/2002-01/msg01229.html; the closest
to consensus was that we should start using 'R' instead of 'r', like
Sun CC does). 

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