re PR c++/28879 (ICE with VLA in template function)

        PR c++/28879
        * parser.c (cp_parser_direct_declarator): In a template, wrap
        non-constant expression in NOP_EXPR with TREE_SIDE_EFFECTS set.
        * pt.c (tsubst): Preserve it in a partial instantiation.
        (dependent_type_p_r): Don't check value_dependent_expression_p.
        * decl.c (compute_array_index_type): Don't check
        value_dependent_expression_p if TREE_SIDE_EFFECTS.

From-SVN: r144988

gcc/cp/ChangeLog

 2009-03-20  Jason Merrill  <jason@redhat.com>
 
+	PR c++/28879
+	* parser.c (cp_parser_direct_declarator): In a template, wrap 
+	non-constant expression in NOP_EXPR with TREE_SIDE_EFFECTS set.
+	* pt.c (tsubst): Preserve it in a partial instantiation.
+	(dependent_type_p_r): Don't check value_dependent_expression_p.
+	* decl.c (compute_array_index_type): Don't check
+	value_dependent_expression_p if TREE_SIDE_EFFECTS.
+
 	C++ core issue 703
 	* typeck2.c (check_narrowing): Don't complain about loss of 
 	precision when converting a floating-point constant.

gcc/cp/decl.c

@@ -7179,13 +7179,22 @@ compute_array_index_type (tree name, tree size)
       type = TREE_TYPE (size);
     }
 
-  if (value_dependent_expression_p (size))
-    {
-      /* We cannot do any checking for a value-dependent SIZE. Just
-	 build the index type and mark that it requires structural
-	 equality checks.  */
+  /* We can only call value_dependent_expression_p on integral constant
+     expressions; the parser adds a dummy NOP_EXPR with TREE_SIDE_EFFECTS
+     set if this isn't one.  */
+  if (processing_template_decl
+      && (TREE_SIDE_EFFECTS (size) || value_dependent_expression_p (size)))
+    {
+      /* We cannot do any checking for a SIZE that isn't known to be
+	 constant. Just build the index type and mark that it requires
+	 structural equality checks.  */
       itype = build_index_type (build_min (MINUS_EXPR, sizetype,
 					   size, integer_one_node));
+      if (!TREE_SIDE_EFFECTS (size))
+	{
+	  TYPE_DEPENDENT_P (itype) = 1;
+	  TYPE_DEPENDENT_P_VALID (itype) = 1;
+	}
       SET_TYPE_STRUCTURAL_EQUALITY (itype);
       return itype;
     }

gcc/cp/parser.c

@@ -13267,6 +13267,13 @@ cp_parser_direct_declarator (cp_parser* parser,
 						 &non_constant_p);
 	      if (!non_constant_p)
 		bounds = fold_non_dependent_expr (bounds);
+	      else if (processing_template_decl)
+		{
+		  /* Remember this wasn't a constant-expression.  */
+		  bounds = build_nop (TREE_TYPE (bounds), bounds);
+		  TREE_SIDE_EFFECTS (bounds) = 1;
+		}
+
 	      /* Normally, the array bound must be an integral constant
 		 expression.  However, as an extension, we allow VLAs
 		 in function scopes.  */

gcc/cp/pt.c

@@ -9084,8 +9084,19 @@ tsubst (tree t, tree args, tsubst_flags_t complain, tree in_decl)
 			   /*integral_constant_expression_p=*/false);
 	max = fold_decl_constant_value (max);
 
+	/* If we're in a partial instantiation, preserve the magic NOP_EXPR
+	   with TREE_SIDE_EFFECTS that indicates this is not an integral
+	   constant expression.  */
+	if (processing_template_decl
+	    && TREE_SIDE_EFFECTS (omax) && TREE_CODE (omax) == NOP_EXPR)
+	  {
+	    gcc_assert (TREE_CODE (max) == NOP_EXPR);
+	    TREE_SIDE_EFFECTS (max) = 1;
+	  }
+
 	if (TREE_CODE (max) != INTEGER_CST
 	    && !at_function_scope_p ()
+	    && !TREE_SIDE_EFFECTS (max)
 	    && !value_dependent_expression_p (max))
 	  {
 	    if (complain & tf_error)
@@ -15972,9 +15983,9 @@ dependent_type_p_r (tree type)
 	   && !TREE_CONSTANT (TYPE_MAX_VALUE (type)))
     {
       /* If this is the TYPE_DOMAIN of an array type, consider it
-	 dependent.  */
-      return (value_dependent_expression_p (TYPE_MAX_VALUE (type))
-	      || type_dependent_expression_p (TYPE_MAX_VALUE (type)));
+	 dependent.  We already checked for value-dependence in
+	 compute_array_index_type.  */
+      return type_dependent_expression_p (TYPE_MAX_VALUE (type));
     }
 
   /* -- a template-id in which either the template name is a template

gcc/testsuite/ChangeLog

+2009-03-21  Jason Merrill  <jason@redhat.com>
+
+	PR c++/28879
+	* g++.dg/ext/vla6.C: New test.
+
 2009-03-20  Jason Merrill  <jason@redhat.com>
 
 	* g++.dg/cpp0x/initlist5.C: Add additional test.

gcc/testsuite/g++.dg/ext/vla6.C

+// PR c++/28879
+// { dg-options "" }
+
+struct A
+{
+  int i;
+  A(): i(1) {}
+};
+
+template<int> void foo()
+{
+  int x[A().i];
+}
+
+void f()
+{
+  foo<1>();
+}