Re: [ob] Adjust member pointer test for g++ 3.3

[Mark Kettenis <mark dot kettenis at xs4all dot nl>]

> Date: Fri, 12 Jan 2007 18:08:03 -0500
> From: Daniel Jacobowitz <drow@false.org>
> 
> On Fri, Jan 12, 2007 at 10:50:27PM +0100, Mark Kettenis wrote:
> > The test now runs for me, but I get quite a few errors.  Here's the
> > resulting bit from gdb.log.  Can you spot what's going wromg here?
> > Should we XFAIL this test for GCC 3.3?
> 
> That depends how we got to some of these bogus conclusions.  I filed
> a GCC bug for the lousy debug info it emits for member pointers; until
> that's fixed, though, I added a workaround in dwarf2read.c.  If there's
> an easy way to extend that to match this too, then it may be helpful to
> do so.
> 
> Do OpenBSD 3.x toolchains use dwarf2?  Or is this out in stabs land?

We're using dwarf2 for a while now.

> > ptype pmi
> > type = int A::**
> > (gdb) FAIL: gdb.cp/member-ptr.exp: ptype pmi (A::j)
> 
> It should be "int A::*".  Somehow we think we have a pointer to a
> member pointer, instead of just a member pointer.  That explains most
> of the cascading failures for pmi.

Here's the relevant readelf -a output:

 <1><11f>: Abbrev Number: 3 (DW_TAG_base_type)
     DW_AT_name        : int    
     DW_AT_byte_size   : 4      
     DW_AT_encoding    : 5      (signed)
...
 <1><177b>: Abbrev Number: 2 (DW_TAG_typedef)
     DW_AT_name        : PMI    
     DW_AT_decl_file   : 1      
     DW_AT_decl_line   : 82     
     DW_AT_type        : <1786> 
 <1><1786>: Abbrev Number: 20 (DW_TAG_pointer_type)
     DW_AT_byte_size   : 8      
     DW_AT_type        : <178c> 
 <1><178c>: Abbrev Number: 47 (DW_TAG_ptr_to_member_type)
     DW_AT_containing_type: <14a7>      
     DW_AT_type        : <11f>  

So it looks like GCC 3.3.5 is emitting bogus debug info.  Do you see a
possibility to deal with that?

> > print a.*pmf
> > $9 = {int (A *, int)} 0x1c000af6 <A::bar(int)>
> > (gdb) PASS: gdb.cp/member-ptr.exp: print a.*pmf
> 
> We get this right...
> 
> > print (a.*pmf)(3)
> > $11 = 127
> > (gdb) FAIL: gdb.cp/member-ptr.exp: print (a.*pmf)(3)
> 
> So I'm pretty surprised that we get this wrong.  We've somehow called
> the wrong function, or called it with a bogus argument / "this" pointer.

Isn't it just another cascading error because initializing members
through data member pointers fails?

Mark

P.S. You still need to submit some bug reports for the gdb/NNN's.