PR c++/89331 - ICE with offsetof in incomplete class.

We were aborting when build_base_path returned an error because of the
derived class not being complete yet, which wasn't considered by the assert.
Fixed by checking for complete type first.  The semantics.c change avoids
a duplicate error message.

	* semantics.c (finish_offsetof): Handle error_mark_node.
	* typeck.c (build_class_member_access_expr): Call
	complete_type_or_maybe_complain before converting to base.

From-SVN: r270135

gcc/cp/ChangeLog

 2019-04-03  Jason Merrill  <jason@redhat.com>
 
+	PR c++/89331 - ICE with offsetof in incomplete class.
+	* semantics.c (finish_offsetof): Handle error_mark_node.
+	* typeck.c (build_class_member_access_expr): Call
+	complete_type_or_maybe_complain before converting to base.
+
 	PR c++/89917 - ICE with lambda in variadic mem-init.
 	* pt.c (make_pack_expansion): Change type_pack_expansion_p to false.
 

gcc/cp/semantics.c

@@ -4144,6 +4144,9 @@ finish_offsetof (tree object_ptr, tree expr, location_t loc)
       return expr;
     }
 
+  if (expr == error_mark_node)
+    return error_mark_node;
+
   if (TREE_CODE (expr) == PSEUDO_DTOR_EXPR)
     {
       error ("cannot apply %<offsetof%> to destructor %<~%T%>",

gcc/cp/typeck.c

@@ -2474,6 +2474,14 @@ build_class_member_access_expr (cp_expr object, tree member,
 	  tree binfo;
 	  base_kind kind;
 
+	  /* We didn't complain above about a currently open class, but now we
+	     must: we don't know how to refer to a base member before layout is
+	     complete.  But still don't complain in a template.  */
+	  if (!dependent_type_p (object_type)
+	      && !complete_type_or_maybe_complain (object_type, object,
+						   complain))
+	    return error_mark_node;
+
 	  binfo = lookup_base (access_path ? access_path : object_type,
 			       member_scope, ba_unique, &kind, complain);
 	  if (binfo == error_mark_node)

gcc/testsuite/g++.dg/ext/builtin-offsetof4.C

+// PR c++/89331
+
+class A {
+public:
+    char a;
+};
+
+class B : public A {
+public:
+    static const unsigned b = __builtin_offsetof(B, a); // { dg-error "incomplete" }
+};

gcc/testsuite/g++.dg/other/offsetof8.C

@@ -9,4 +9,4 @@ struct B: virtual A { };
 int a[]  = {
   !&((B*)0)->i,    // { dg-error "invalid access to non-static data member" }
   __builtin_offsetof (B, i)   // { dg-error "invalid access to non-static" }
-};			      // { dg-message "offsetof within non-standard-layout type" "" { target *-*-* } .-1 }
+};