Patchwork [1/3] Disambiguate nested objc-message-expressions and c++11 attributes

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Submitter Dodji Seketeli
Date Oct. 9, 2012, 9:22 p.m.
Message ID <87sj9ne3x9.fsf@redhat.com>
Download mbox | patch
Permalink /patch/190455/
State New
Headers show

Comments

Dodji Seketeli - Oct. 9, 2012, 9:22 p.m.
Hello,

A couple of obj-c++ tests were failing[1] because the tokens '[[' can
either be the beginning of a c++11 attribute (that is itself at the
beginning of a statement), or the beginning of a nested
objc-message-expression.  This patch resolves the ambiguity by
tentatively parsing the c++11 attribute and if it fails, then consider
the objc-message-expression.

I missed this initially because it didn't occur to me that
--enable-languages=all,ada does not include obj-c++.  Shame on me.  I
have now updated my compile farm scripts to use
--enable-language=all,ada,obj-c++,go and I

[1]:

FAIL: obj-c++.dg/syntax-error-6.mm -fgnu-runtime  (test for errors, line 11)
FAIL: obj-c++.dg/syntax-error-6.mm -fgnu-runtime (test for excess errors)
FAIL: obj-c++.dg/template-8.mm -fgnu-runtime (test for excess errors)

Tested on x86_64-unknown-linux-gnu against trunk.

gcc/cp/

	* parser (cp_parser_statement):  Parse c++11 attributes tentatively.
	(cp_parser_std_attribute_spec_seq): Do not warn too early about
	using c++11 attributes in non c++11 mode.
---
 gcc/cp/parser.c | 15 ++++++++++++++-
 1 file changed, 14 insertions(+), 1 deletion(-)

Patch

diff --git a/gcc/cp/parser.c b/gcc/cp/parser.c
index 52a152d..0f950db 100644
--- a/gcc/cp/parser.c
+++ b/gcc/cp/parser.c
@@ -8716,7 +8716,17 @@  cp_parser_statement (cp_parser* parser, tree in_statement_expr,
 
   cp_lexer_save_tokens (parser->lexer);
   attrs_location = cp_lexer_peek_token (parser->lexer)->location;
+  if (c_dialect_objc ())
+    /* In obj-c++, seing '[[' might be the either the beginning of
+       c++11 attributes, or a nested objc-message-expression.  So
+       let's parse the c++11 attributes tentatively.  */
+    cp_parser_parse_tentatively (parser);
   std_attrs = cp_parser_std_attribute_spec_seq (parser);
+  if (c_dialect_objc ())
+    {
+      if (!cp_parser_parse_definitely (parser))
+	std_attrs = NULL_TREE;
+    }
 
   /* Peek at the next token.  */
   token = cp_lexer_peek_token (parser->lexer);
@@ -20701,7 +20711,6 @@  cp_parser_std_attribute_spec (cp_parser *parser)
       && cp_lexer_peek_nth_token (parser->lexer, 2)->type == CPP_OPEN_SQUARE)
     {
       cp_lexer_consume_token (parser->lexer);
-      maybe_warn_cpp0x (CPP0X_ATTRIBUTES);
       cp_lexer_consume_token (parser->lexer);
 
       attributes = cp_parser_std_attribute_list (parser);
@@ -20709,6 +20718,10 @@  cp_parser_std_attribute_spec (cp_parser *parser)
       if (!cp_parser_require (parser, CPP_CLOSE_SQUARE, RT_CLOSE_SQUARE)
 	  || !cp_parser_require (parser, CPP_CLOSE_SQUARE, RT_CLOSE_SQUARE))
 	cp_parser_skip_to_end_of_statement (parser);
+      else
+	/* Warn about parsing c++11 attribute in non-c++1 mode, only
+	   when we are sure that we have actually parsed them.  */
+	maybe_warn_cpp0x (CPP0X_ATTRIBUTES);
     }
   else
     {