re PR c++/28903 (Rejects VLA in template class's member with using)

[gcc.git] / gcc / cp / pt.c

diff --git a/gcc/cp/pt.c b/gcc/cp/pt.c
index d278b00448ee07d8d97bcefeaef89bf947f10945..715b9461aba4bf8d4e79e032522cfe833639938d 100644 (file)
--- a/gcc/cp/pt.c
+++ b/gcc/cp/pt.c
@@ -7216,9 +7216,9 @@ tsubst (tree t, tree args, tsubst_flags_t complain, tree in_decl)
       {
        tree max, omax = TREE_OPERAND (TYPE_MAX_VALUE (t), 0);
 
-       /* The array dimension behaves like a non-type template arg,
-          in that we want to fold it as much as possible.  */
-       max = tsubst_template_arg (omax, args, complain, in_decl);
+       max = tsubst_expr (omax, args, complain, in_decl,
+                          /*integral_constant_expression_p=*/false);
+       max = fold_non_dependent_expr (max);
        max = fold_decl_constant_value (max);
 
        if (TREE_CODE (max) != INTEGER_CST 
@@ -10618,21 +10618,56 @@ unify (tree tparms, tree targs, tree parm, tree arg, int strict)
        {
          tree parm_max;
          tree arg_max;
-
-         parm_max = TYPE_MAX_VALUE (TYPE_DOMAIN (parm));
-         arg_max = TYPE_MAX_VALUE (TYPE_DOMAIN (arg));
+         bool parm_cst;
+         bool arg_cst;
 
          /* Our representation of array types uses "N - 1" as the
             TYPE_MAX_VALUE for an array with "N" elements, if "N" is
-            not an integer constant.  */
-         if (TREE_CODE (parm_max) == MINUS_EXPR)
+            not an integer constant.  We cannot unify arbitrarily
+            complex expressions, so we eliminate the MINUS_EXPRs
+            here.  */
+         parm_max = TYPE_MAX_VALUE (TYPE_DOMAIN (parm));
+         parm_cst = TREE_CODE (parm_max) == INTEGER_CST;
+         if (!parm_cst)
            {
-             arg_max = fold_build2 (PLUS_EXPR,
-                                    integer_type_node,
-                                    arg_max,
-                                    TREE_OPERAND (parm_max, 1));
+             gcc_assert (TREE_CODE (parm_max) == MINUS_EXPR);
              parm_max = TREE_OPERAND (parm_max, 0);
            }
+         arg_max = TYPE_MAX_VALUE (TYPE_DOMAIN (arg));
+         arg_cst = TREE_CODE (arg_max) == INTEGER_CST;
+         if (!arg_cst)
+           {
+             /* The ARG_MAX may not be a simple MINUS_EXPR, if we are
+                trying to unify the type of a variable with the type
+                of a template parameter.  For example:
+
+                   template <unsigned int N>
+                  void f (char (&) [N]);
+                  int g(); 
+                  void h(int i) {
+                     char a[g(i)];
+                    f(a); 
+                   }
+
+                Here, the type of the ARG will be "int [g(i)]", and
+                may be a SAVE_EXPR, etc.  */
+             if (TREE_CODE (arg_max) != MINUS_EXPR)
+               return 1;
+             arg_max = TREE_OPERAND (arg_max, 0);
+           }
+
+         /* If only one of the bounds used a MINUS_EXPR, compensate
+            by adding one to the other bound.  */
+         if (parm_cst && !arg_cst)
+           parm_max = fold_build2 (PLUS_EXPR,
+                                   integer_type_node,
+                                   parm_max,
+                                   integer_one_node);
+         else if (arg_cst && !parm_cst)
+           arg_max = fold_build2 (PLUS_EXPR,
+                                  integer_type_node,
+                                  arg_max,
+                                  integer_one_node);
 
          if (unify (tparms, targs, parm_max, arg_max, UNIFY_ALLOW_INTEGER))
            return 1;