Re: [RFA/dwarf-2] Fix for the null record problem

[Elena Zannoni <ezannoni at redhat dot com>]

Joel Brobecker writes:
 > Hello,
 > 
 > This is a followup on the thread that started with:
 > 
 >    http://sources.redhat.com/ml/gdb-patches/2004-02/msg00058.html
 > 
 > The test proposed under that thread was dropped because an empty
 > struct is not legal C. However, it is legal in Ada, and I've seen
 > a message saying that it is also legal in C++.
 > 

Let's try the Vulcan mind meld: "We need a gdb.ada directory. We need
a gdb.ada directory. We need a gdb.ada directory. We need a gdb.ada
directory." :-) 

Seriously, I'd like to see a testcase that FAIL->PASS with this patch.
Can somebody get a C++ testcase, at least?

the patch looks sensible, but I would like to see the testcase go in
at the same time, or we'll forget.

elena


 > I have found the source of the problem, and suggest the attached patch.
 > The problem was that GDB was mistakenly deducing that the empry record
 > was only a stub because of the lack of fields, and was therefore tagging
 > it with TYPE_FLAG_STUB. This is not correct. Instead, the right
 > approach, I believe, is to check for the DW_AT_declaration attribute.
 > 
 > 2004-02-19  J. Brobecker  <brobecker@gnat.com>
 > 
 >         * dwarf2read.c (read_structure_scope): Identify stub types
 >         using the DW_AT_declaration attribute.
 > 
 > tested on x86-linux. No regression. Fixes the testcase that was
 > proposed by Andrew (even though it is not legal C) and the Ada
 > case.
 > 
 > OK to apply?
 > 
 > Thanks,
 > -- 
 > Joel
 > 
 > PS: BTW, my past 3 months of traveling will soon be over. The past
 > couple of weeks have been very hectic. I have noticed that there were
 > some messages directed at me to which I haven't answered yet. I am
 > really sorry. I have kept these messages and will try to answer them
 > soon.
 > Index: dwarf2read.c
 > ===================================================================
 > RCS file: /cvs/src/src/gdb/dwarf2read.c,v
 > retrieving revision 1.130
 > diff -u -p -r1.130 dwarf2read.c
 > --- dwarf2read.c	28 Jan 2004 18:43:06 -0000	1.130
 > +++ dwarf2read.c	19 Feb 2004 13:58:42 -0000
 > @@ -3077,6 +3077,9 @@ read_structure_scope (struct die_info *d
 >        TYPE_LENGTH (type) = 0;
 >      }
 >  
 > +  if (dwarf2_attr (die, DW_AT_declaration, cu) != NULL)
 > +    TYPE_FLAGS (type) |= TYPE_FLAG_STUB;
 > +
 >    /* We need to add the type field to the die immediately so we don't
 >       infinitely recurse when dealing with pointers to the structure
 >       type within the structure itself. */
 > @@ -3213,11 +3216,6 @@ read_structure_scope (struct die_info *d
 >        new_symbol (die, type, cu);
 >  
 >        do_cleanups (back_to);
 > -    }
 > -  else
 > -    {
 > -      /* No children, must be stub. */
 > -      TYPE_FLAGS (type) |= TYPE_FLAG_STUB;
 >      }
 >  
 >    processing_current_prefix = previous_prefix;