[C++ PATCH] Fix parser ICE with [[...]] and [[unused,...]] (PR c++/77637)

[Jakub Jelinek]

Hi!

As the testcase shows, while the grammar has
attribute-list:
  attribute[opt]
  attribute-list , attribute[opt]
  attribute ...
  attribute-list , attribute ...
we are actually parsing it as if the last 2 lines were
  attribute[opt] ...
  attribute-list , attribute[opt] ...
and ICEing when there is no attribute.
Fixed thusly, bootstrapped/regtested on x86_64-linux and i686-linux, ok for
trunk/6.3?

2016-09-19  Jakub Jelinek  <ja...@redhat.com>

        PR c++/77637
        * parser.c (cp_parser_std_attribute_list): Reject ... without
        preceding attribute.

        * g++.dg/cpp0x/gen-attrs-62.C: New test.

--- gcc/cp/parser.c.jj  2016-09-16 22:19:39.000000000 +0200
+++ gcc/cp/parser.c     2016-09-19 10:33:51.481904739 +0200
@@ -24220,8 +24220,12 @@ cp_parser_std_attribute_list (cp_parser
       if (token->type == CPP_ELLIPSIS)
        {
          cp_lexer_consume_token (parser->lexer);
-         TREE_VALUE (attribute)
-           = make_pack_expansion (TREE_VALUE (attribute));
+         if (attribute == NULL_TREE)
+           error_at (token->location,
+                     "expected attribute before %<...%>");
+         else
+           TREE_VALUE (attribute)
+             = make_pack_expansion (TREE_VALUE (attribute));
          token = cp_lexer_peek_token (parser->lexer);
        }
       if (token->type != CPP_COMMA)
--- gcc/testsuite/g++.dg/cpp0x/gen-attrs-62.C.jj        2016-09-19 
10:37:59.414772726 +0200
+++ gcc/testsuite/g++.dg/cpp0x/gen-attrs-62.C   2016-09-19 10:37:28.000000000 
+0200
@@ -0,0 +1,5 @@
+// PR c++/77637
+// { dg-do compile { target c++11 } }
+
+int [[...]] a;         // { dg-error "expected attribute before '...'" }
+int [[,,...]] b;       // { dg-error "expected attribute before '...'" }

        Jakub