PR c++/91391 - bogus -Wcomma-subscript warning.

	* parser.c (cp_parser_postfix_open_square_expression): Don't warn about
	a deprecated comma here.  Pass warn_comma_subscript down to
	cp_parser_expression.
	(cp_parser_expression): New bool parameter.  Warn about uses of a comma
	operator within a subscripting expression.
	(cp_parser_skip_to_closing_square_bracket): Revert to pre-r274121 state.
	(cp_parser_skip_to_closing_square_bracket_1): Remove.

	* g++.dg/cpp2a/comma5.C: New test.

Co-Authored-By: Marek Polacek <polacek@redhat.com>

From-SVN: r274483

4 files changed, 63 insertions, 74 deletions

diff --git a/gcc/cp/ChangeLog b/gcc/cp/ChangeLog
index 186ee7b..8fee045 100644
--- a/gcc/cp/ChangeLog
+++ b/gcc/cp/ChangeLog
@@ -1,3 +1,15 @@
+2019-08-14  Jakub Jelinek  <jakub@redhat.com>
+	    Marek Polacek  <polacek@redhat.com>
+
+	PR c++/91391 - bogus -Wcomma-subscript warning.
+	* parser.c (cp_parser_postfix_open_square_expression): Don't warn about
+	a deprecated comma here.  Pass warn_comma_subscript down to
+	cp_parser_expression.
+	(cp_parser_expression): New bool parameter.  Warn about uses of a comma
+	operator within a subscripting expression.
+	(cp_parser_skip_to_closing_square_bracket): Revert to pre-r274121 state.
+	(cp_parser_skip_to_closing_square_bracket_1): Remove.
+
 2019-08-14  Jonathan Wakely  <jwakely@redhat.com>
 
 	* name-lookup.c (get_std_name_hint): Add more entries.
diff --git a/gcc/cp/parser.c b/gcc/cp/parser.c
index b56cc69..dbbfe1d 100644
--- a/gcc/cp/parser.c
+++ b/gcc/cp/parser.c
@@ -2102,7 +2102,7 @@ static cp_expr cp_parser_assignment_expression
 static enum tree_code cp_parser_assignment_operator_opt
   (cp_parser *);
 static cp_expr cp_parser_expression
-  (cp_parser *, cp_id_kind * = NULL, bool = false, bool = false);
+  (cp_parser *, cp_id_kind * = NULL, bool = false, bool = false, bool = false);
 static cp_expr cp_parser_constant_expression
   (cp_parser *, bool = false, bool * = NULL, bool = false);
 static cp_expr cp_parser_builtin_offsetof
@@ -2669,8 +2669,6 @@ static bool cp_parser_init_statement_p
   (cp_parser *);
 static bool cp_parser_skip_to_closing_square_bracket
   (cp_parser *);
-static int cp_parser_skip_to_closing_square_bracket_1
-  (cp_parser *, enum cpp_ttype);
 
 /* Concept-related syntactic transformations */
 
@@ -7524,33 +7522,9 @@ cp_parser_postfix_open_square_expression (cp_parser *parser,
 	  index = cp_parser_braced_list (parser, &expr_nonconst_p);
 	}
       else
-	{
-	  /* [depr.comma.subscript]: A comma expression appearing as
-	     the expr-or-braced-init-list of a subscripting expression
-	     is deprecated.  A parenthesized comma expression is not
-	     deprecated.  */
-	  if (warn_comma_subscript)
-	    {
-	      /* Save tokens so that we can put them back.  */
-	      cp_lexer_save_tokens (parser->lexer);
-
-	      /* Look for ',' that is not nested in () or {}.  */
-	      if (cp_parser_skip_to_closing_square_bracket_1 (parser,
-							      CPP_COMMA) == -1)
-		{
-		  auto_diagnostic_group d;
-		  warning_at (cp_lexer_peek_token (parser->lexer)->location,
-			      OPT_Wcomma_subscript,
-			      "top-level comma expression in array subscript "
-			      "is deprecated");
-		}
-
-	      /* Roll back the tokens we skipped.  */
-	      cp_lexer_rollback_tokens (parser->lexer);
-	    }
-
-	  index = cp_parser_expression (parser);
-	}
+	index = cp_parser_expression (parser, NULL, /*cast_p=*/false,
+				      /*decltype_p=*/false,
+				      /*warn_comma_p=*/warn_comma_subscript);
     }
 
   parser->greater_than_is_operator_p = saved_greater_than_is_operator_p;
@@ -9932,12 +9906,13 @@ cp_parser_assignment_operator_opt (cp_parser* parser)
    CAST_P is true if this expression is the target of a cast.
    DECLTYPE_P is true if this expression is the immediate operand of decltype,
      except possibly parenthesized or on the RHS of a comma (N3276).
+   WARN_COMMA_P is true if a comma should be diagnosed.
 
    Returns a representation of the expression.  */
 
 static cp_expr
 cp_parser_expression (cp_parser* parser, cp_id_kind * pidk,
-		      bool cast_p, bool decltype_p)
+		      bool cast_p, bool decltype_p, bool warn_comma_p)
 {
   cp_expr expression = NULL_TREE;
   location_t loc = UNKNOWN_LOCATION;
@@ -9984,6 +9959,17 @@ cp_parser_expression (cp_parser* parser, cp_id_kind * pidk,
 	break;
       /* Consume the `,'.  */
       loc = cp_lexer_peek_token (parser->lexer)->location;
+      if (warn_comma_p)
+	{
+	  /* [depr.comma.subscript]: A comma expression appearing as
+	     the expr-or-braced-init-list of a subscripting expression
+	     is deprecated.  A parenthesized comma expression is not
+	     deprecated.  */
+	  warning_at (loc, OPT_Wcomma_subscript,
+		      "top-level comma expression in array subscript "
+		      "is deprecated");
+	  warn_comma_p = false;
+	}
       cp_lexer_consume_token (parser->lexer);
       /* A comma operator cannot appear in a constant-expression.  */
       if (cp_parser_non_integral_constant_expression (parser, NIC_COMMA))
@@ -22888,25 +22874,16 @@ cp_parser_braced_list (cp_parser* parser, bool* non_constant_p)
 }
 
 /* Consume tokens up to, and including, the next non-nested closing `]'.
-   Returns 1 iff we found a closing `]'.  Returns -1 if OR_TTYPE is not
-   CPP_EOF and we found an unnested token of that type.  */
+   Returns true iff we found a closing `]'.  */
 
-static int
-cp_parser_skip_to_closing_square_bracket_1 (cp_parser *parser,
-					    enum cpp_ttype or_ttype)
+static bool
+cp_parser_skip_to_closing_square_bracket (cp_parser *parser)
 {
   unsigned square_depth = 0;
-  unsigned paren_depth = 0;
-  unsigned brace_depth = 0;
 
   while (true)
     {
-      cp_token *token = cp_lexer_peek_token (parser->lexer);
-
-      /* Have we found what we're looking for before the closing square?  */
-      if (token->type == or_ttype && or_ttype != CPP_EOF
-	  && brace_depth == 0 && paren_depth == 0 && square_depth == 0)
-	return -1;
+      cp_token * token = cp_lexer_peek_token (parser->lexer);
 
       switch (token->type)
 	{
@@ -22916,38 +22893,20 @@ cp_parser_skip_to_closing_square_bracket_1 (cp_parser *parser,
 	  /* FALLTHRU */
 	case CPP_EOF:
 	  /* If we've run out of tokens, then there is no closing `]'.  */
-	  return 0;
+	  return false;
 
         case CPP_OPEN_SQUARE:
           ++square_depth;
           break;
 
         case CPP_CLOSE_SQUARE:
-	  if (square_depth-- == 0)
+	  if (!square_depth--)
 	    {
 	      cp_lexer_consume_token (parser->lexer);
-	      return 1;
+	      return true;
 	    }
 	  break;
 
-	case CPP_OPEN_BRACE:
-	  ++brace_depth;
-	  break;
-
-	case CPP_CLOSE_BRACE:
-	  if (brace_depth-- == 0)
-	    return 0;
-	  break;
-
-	case CPP_OPEN_PAREN:
-	  ++paren_depth;
-	  break;
-
-	case CPP_CLOSE_PAREN:
-	  if (paren_depth-- == 0)
-	    return 0;
-	  break;
-
 	default:
 	  break;
 	}
@@ -22957,15 +22916,6 @@ cp_parser_skip_to_closing_square_bracket_1 (cp_parser *parser,
     }
 }
 
-/* Consume tokens up to, and including, the next non-nested closing `]'.
-   Returns true iff we found a closing `]'.  */
-
-static bool
-cp_parser_skip_to_closing_square_bracket (cp_parser *parser)
-{
-  return cp_parser_skip_to_closing_square_bracket_1 (parser, CPP_EOF) == 1;
-}
-
 /* Return true if we are looking at an array-designator, false otherwise.  */
 
 static bool
diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog
index 3a5155e..db9cba6 100644
--- a/gcc/testsuite/ChangeLog
+++ b/gcc/testsuite/ChangeLog
@@ -1,3 +1,9 @@
+2019-08-14  Jakub Jelinek  <jakub@redhat.com>
+	    Marek Polacek  <polacek@redhat.com>
+
+	PR c++/91391 - bogus -Wcomma-subscript warning.
+	* g++.dg/cpp2a/comma5.C: New test.
+
 2019-08-14  Christophe Lyon  <christophe.lyon@linaro.org>
 
 	* lib/target-supports.exp (check_effective_target_noinit): New
diff --git a/gcc/testsuite/g++.dg/cpp2a/comma5.C b/gcc/testsuite/g++.dg/cpp2a/comma5.C
new file mode 100644
index 0000000..68d19c0
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp2a/comma5.C
@@ -0,0 +1,21 @@
+// PR c++/91391 - bogus -Wcomma-subscript warning.
+// { dg-do compile { target c++2a } }
+
+template<typename T, typename U>
+int foo(T t, U u) { return t + u; }
+
+void
+fn (int *a, int b, int c)
+{
+  a[foo<int, int>(1, 2)];
+  a[foo<int, int>(1, 2), foo<int, int>(3, 4)]; // { dg-warning "24:top-level comma expression in array subscript is deprecated" }
+
+  a[b < c, b < c]; // { dg-warning "top-level comma expression in array subscript is deprecated" }
+  a[b < c, b > c]; // { dg-warning "top-level comma expression in array subscript is deprecated" }
+  a[b > c, b > c]; // { dg-warning "top-level comma expression in array subscript is deprecated" }
+  a[b > c, b < c]; // { dg-warning "top-level comma expression in array subscript is deprecated" }
+  a[(b < c, b < c)];
+  a[(b < c, b > c)];
+  a[b << c, b << c]; // { dg-warning "top-level comma expression in array subscript is deprecated" }
+  a[(b << c, b << c)]; 
+}