[C++ Patch] PR 58503

[Paolo Carlini]

Hi,

in this error recovery issue in template context, 
do_range_for_auto_deduction calls cp_parser_perform_range_for_lookup, 
which can't resolve begin/end and eventually crashes because TREE_TYPE 
(*begin) and TREE_TYPE (*end) are NULL_TREE.

It doesn't seem correct to simply early return error_mark_node, because 
the errors at issue are the permerror(s) produced by 
unqualified_fn_lookup_error. However, returning NULL_TREE, while 
adjusting do_range_for_auto_deduction to do nothing when the return type 
of begin/end isn't known, like in the case at issue, appears to work 
fine (I also checked that with -fpermissive an eventual instantiation 
produces hard errors, as it should)

Tested x86_64-linux.

Thanks,
Paolo.

////////////////////////


/cp
2013-10-03  Paolo Carlini  <paolo.carl...@oracle.com>

        PR c++/58503
        * parser.c (cp_parser_perform_range_for_lookup): If either TREE_TYPE
        of *begin or *end is NULL_TREE, return NULL_TREE.
        (do_range_for_auto_deduction): If cp_parser_perform_range_for_lookup
        returns NULL_TREE, don't actually do_auto_deduction.

/testsuite
2013-10-03  Paolo Carlini  <paolo.carl...@oracle.com>

        PR c++/58503
        * g++.dg/cpp0x/range-for26.C: New.
Index: cp/parser.c
===================================================================
--- cp/parser.c (revision 203152)
+++ cp/parser.c (working copy)
@@ -9960,11 +9960,15 @@ do_range_for_auto_deduction (tree decl, tree range
       range_temp = convert_from_reference (build_range_temp (range_expr));
       iter_type = (cp_parser_perform_range_for_lookup
                   (range_temp, &begin_dummy, &end_dummy));
-      iter_decl = build_decl (input_location, VAR_DECL, NULL_TREE, iter_type);
-      iter_decl = build_x_indirect_ref (input_location, iter_decl, RO_NULL,
-                                       tf_warning_or_error);
-      TREE_TYPE (decl) = do_auto_deduction (TREE_TYPE (decl),
-                                           iter_decl, auto_node);
+      if (iter_type)
+       {
+         iter_decl = build_decl (input_location, VAR_DECL, NULL_TREE,
+                                 iter_type);
+         iter_decl = build_x_indirect_ref (input_location, iter_decl, RO_NULL,
+                                           tf_warning_or_error);
+         TREE_TYPE (decl) = do_auto_deduction (TREE_TYPE (decl),
+                                               iter_decl, auto_node);
+       }
     }
 }
 
@@ -10171,6 +10175,10 @@ cp_parser_perform_range_for_lookup (tree range, tr
          *begin = *end = error_mark_node;
          return error_mark_node;
        }
+      else if (!TREE_TYPE (*begin) || !TREE_TYPE (*end))
+       /* Can happen, when, eg, in a template context, Koenig lookup
+          can't resolve begin/end (c++/58503).  */
+       return NULL_TREE;
       else
        {
          tree iter_type = cv_unqualified (TREE_TYPE (*begin));
Index: testsuite/g++.dg/cpp0x/range-for26.C
===================================================================
--- testsuite/g++.dg/cpp0x/range-for26.C        (revision 0)
+++ testsuite/g++.dg/cpp0x/range-for26.C        (working copy)
@@ -0,0 +1,7 @@
+// PR c++/58503
+// { dg-require-effective-target c++11 }
+
+template<int> void foo()
+{
+  for (auto i : 0) {}  // { dg-error "there are no arguments" }
+}