C++ PATCH for c++/47301 (ICE with constexpr, array and -fabi-version=1)

[Jason Merrill <jason at redhat dot com>]

The code for backwards-compatibility with ABI v1 didn't do too well with 
the case of a literal class used as an array bound; it built up an 
integral MINUS_EXPR with it directly, which doesn't make much sense. 
But since 3.2 didn't support constexpr, we can just disable the v1 
semantics when we are dealing with a literal class.

Tested x86_64-pc-linux-gnu, applying to trunk.
commit 59ffa184c154ed0676af737645f6b0a34f49dc02
Author: Jason Merrill <jason@redhat.com>
Date:   Wed Mar 16 21:12:23 2011 -0400

    	PR c++/47301
    	* decl.c (compute_array_index_type): Don't bother trying to deal
    	with literal classes in ABI v1.

diff --git a/gcc/cp/decl.c b/gcc/cp/decl.c
index 17b3163..a7da574 100644
--- a/gcc/cp/decl.c
+++ b/gcc/cp/decl.c
@@ -7525,6 +7525,9 @@ compute_array_index_type (tree name, tree size, tsubst_flags_t complain)
 	      if (size == error_mark_node)
 		return error_mark_node;
 	      type = TREE_TYPE (size);
+	      /* We didn't support this case in GCC 3.2, so don't bother
+		 trying to model it now in ABI v1.  */
+	      abi_1_itype = error_mark_node;
 	    }
 
 	  size = maybe_constant_value (size);
@@ -7569,7 +7572,8 @@ compute_array_index_type (tree name, tree size, tsubst_flags_t complain)
       return itype;
     }
   
-  if (!abi_version_at_least (2) && processing_template_decl)
+  if (!abi_version_at_least (2) && processing_template_decl
+      && abi_1_itype == NULL_TREE)
     /* For abi-1, we handled all instances in templates the same way,
        even when they were non-dependent. This affects the manglings
        produced.  So, we do the normal checking for non-dependent
@@ -7683,7 +7687,7 @@ compute_array_index_type (tree name, tree size, tsubst_flags_t complain)
     }
 
   /* Create and return the appropriate index type.  */
-  if (abi_1_itype)
+  if (abi_1_itype && abi_1_itype != error_mark_node)
     {
       tree t = build_index_type (itype);
       TYPE_CANONICAL (abi_1_itype) = TYPE_CANONICAL (t);
diff --git a/gcc/testsuite/g++.dg/cpp0x/constexpr-abi1.C b/gcc/testsuite/g++.dg/cpp0x/constexpr-abi1.C
new file mode 100644
index 0000000..e83f142
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp0x/constexpr-abi1.C
@@ -0,0 +1,16 @@
+// PR c++/47301
+// { dg-options "-std=c++0x -fabi-version=1" }
+
+struct A
+{
+  constexpr operator int ()
+  {
+    return 1;
+  }
+};
+
+template < int > struct B
+{
+  static constexpr A a = A();
+  int ar[a];
+};