[C++ Patch] PR 53761

[Paolo Carlini]

Hi,

in this PR, at variance with the C front-end, we don't check well enough 
the aggregate type - in finish_struct_1 - and we ICE later. Then I'm 
essentially copying from the C front-end the check. Some details:

1- In these checks, eg, no fields too, the C front-end only warns, 
zeroes TYPE_TRANSPARENT_AGGR and continues. We emit an hard error and 
zero TYPE_TRANSPARENT_AGGR as error recovery measure. I'm doing the same 
for this additional check.

2- The existing diagnostics, eg, for no fields, again, talks about 
"class", I think we can distinguish "class" vs "union" (when it makes 
sense, I'm leaving alone bases, virtuals, already rejected by the parser 
for unions)

Tested x86_64-linux, as usual.

Thanks,
Paolo.

//////////////////////////
/cp
2012-10-10  Paolo Carlini  <paolo.carl...@oracle.com>

        PR c++/53761
        * class.c (finish_struct_1): Reject aggregates decorated with
        __transparent_union__ which cannot be made transparent.

/testsuite
2012-10-10  Paolo Carlini  <paolo.carl...@oracle.com>

        PR c++/53761
        * g++.dg/ext/transparent-union.C: New.
Index: cp/class.c
===================================================================
--- cp/class.c  (revision 192309)
+++ cp/class.c  (working copy)
@@ -6181,7 +6181,10 @@ finish_struct_1 (tree t)
       tree field = first_field (t);
       if (field == NULL_TREE || error_operand_p (field))
        {
-         error ("type transparent class %qT does not have any fields", t);
+         if (TREE_CODE (t) == UNION_TYPE)
+           error ("type transparent union %qT does not have any fields", t);
+         else
+           error ("type transparent class %qT does not have any fields", t);
          TYPE_TRANSPARENT_AGGR (t) = 0;
        }
       else if (DECL_ARTIFICIAL (field))
@@ -6195,6 +6198,14 @@ finish_struct_1 (tree t)
            }
          TYPE_TRANSPARENT_AGGR (t) = 0;
        }
+      else if (TYPE_MODE (t) != DECL_MODE (field))
+       {
+         if (TREE_CODE (t) == UNION_TYPE)
+           error ("type transparent union %qT cannot be made transparent", t);
+         else
+           error ("type transparent class %qT cannot be made transparent", t);
+         TYPE_TRANSPARENT_AGGR (t) = 0;
+       }
     }
 }
 
Index: testsuite/g++.dg/ext/transparent-union.C
===================================================================
--- testsuite/g++.dg/ext/transparent-union.C    (revision 0)
+++ testsuite/g++.dg/ext/transparent-union.C    (working copy)
@@ -0,0 +1,5 @@
+// PR c++/53761
+
+typedef union {    // { dg-error "transparent union" }
+   double x;
+} __attribute__(( __transparent_union__ )) example_t;