[Bug debug/45997] [4.6 Regression] __unknown__ type name for typedef'd int

["dodji at gcc dot gnu.org" <gcc-bugzilla at gcc dot gnu dot org>]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=45997

--- Comment #4 from Dodji Seketeli <dodji at gcc dot gnu.org> 2010-11-08 22:39:09 UTC ---
At some point modified_type_die is called for volatile_const_my_int with
is_volatile and is_const_type set to 0, meaning we want to emit the DIE
of the cv-unqualified version of volatile_const_my_int i.e, my_int.

The problem is that the line

  /* See if we already have the appropriately qualified variant of
     this type.  */
  qualified_type
    = get_qualified_type (type,
              ((is_const_type ? TYPE_QUAL_CONST : 0)
               | (is_volatile_type ? TYPE_QUAL_VOLATILE : 0)));

fails to give us the the my_int (cv-unqualified version of
volatile_const_my_int) we want and returns NULL instead. That's because
get_qualified_type doesn't look through typedefs as it must preserve
TYPE_NAMEs (see the comment in get_qualified_type). From this point, I
think we are likely to loose.

So, maybe if we try harder to come up with the cv-unqualified version of
the input type, things will get better?

This patch that (only lightly tested seems) to fix the problem too. What
do you think?

diff --git a/gcc/dwarf2out.c b/gcc/dwarf2out.c
index 9bb569b..f639e24 100644
--- a/gcc/dwarf2out.c
+++ b/gcc/dwarf2out.c
@@ -12715,6 +12715,19 @@ modified_type_die (tree type, int is_const_type, int
is_volatile_type,
               ((is_const_type ? TYPE_QUAL_CONST : 0)
                | (is_volatile_type ? TYPE_QUAL_VOLATILE : 0)));

+  /* If TYPE is a typedef and we want its cv-unqualified version,
+     get_qualified_type just returns NULL because it doesn't look
+     through typedefs; In that case, let's use the underlying type of
+     the typedef.  */
+  if (qualified_type == NULL
+      && typedef_variant_p (type)
+      && (is_const_type < TYPE_READONLY (type)
+      || is_volatile_type < TYPE_VOLATILE (type)))
+    qualified_type =
+      get_qualified_type (DECL_ORIGINAL_TYPE (TYPE_NAME (type)),
+              ((is_const_type ? TYPE_QUAL_CONST : 0)
+               | (is_volatile_type ? TYPE_QUAL_VOLATILE : 0)));
+
   if (qualified_type == sizetype
       && TYPE_NAME (qualified_type)
       && TREE_CODE (TYPE_NAME (qualified_type)) == TYPE_DECL)