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

[Joel Brobecker <brobecker@gnat.com>]

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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++.

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.

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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;