PR c/71171: Fix uninitialized source_range in c_parser_postfix_expression

A common way for a c_expr to have an uninitialized src_range is in
error-handling, where the "value" field is set to error_mark_node
without touching the src_range, leading to complaints from valgrind.

This patch introduces a new method c_expr::set_error which sets
the value to error_mark_node whilst initializing the src_range to
UNKNOWN_LOCATION.

This fixes the valgrind issue seen in PR c/71171, along with various
other related issues seen when running the testsuite using the
checker patch I posted here:
  https://gcc.gnu.org/ml/gcc-patches/2015-12/msg00887.html
(this checker still doesn't fully work yet, but it seems to be good
for easily detecting these issues without needing Valgrind).

gcc/c/ChangeLog:
	PR c/71171
	* c-parser.c (c_parser_generic_selection): Use c_expr::set_error
	in error-handling.
	(c_parser_postfix_expression): Likewise.
	* c-tree.h (c_expr::set_error): New method.
	* c-typeck.c (parser_build_binary_op): In error-handling, ensure
	that result's range is initialized.



git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@236488 138bc75d-0d04-0410-961f-82ee72b054a4

4 files changed, 61 insertions, 37 deletions

diff --git a/gcc/c/ChangeLog b/gcc/c/ChangeLog
index 476718fa631..5731048b087 100644
--- a/gcc/c/ChangeLog
+++ b/gcc/c/ChangeLog
@@ -1,3 +1,13 @@
+2016-05-19  David Malcolm  <dmalcolm@redhat.com>
+
+	PR c/71171
+	* c-parser.c (c_parser_generic_selection): Use c_expr::set_error
+	in error-handling.
+	(c_parser_postfix_expression): Likewise.
+	* c-tree.h (c_expr::set_error): New method.
+	* c-typeck.c (parser_build_binary_op): In error-handling, ensure
+	that result's range is initialized.
+
 2016-05-17  James Greenhalgh  <james.greenhalgh@arm.com>
 
 	* c-typeck.c (parser_build_unary_op): Fix formatting.
diff --git a/gcc/c/c-parser.c b/gcc/c/c-parser.c
index 6523c08d63f..c2c83143c05 100644
--- a/gcc/c/c-parser.c
+++ b/gcc/c/c-parser.c
@@ -7194,7 +7194,7 @@ c_parser_generic_selection (c_parser *parser)
 
   error_expr.original_code = ERROR_MARK;
   error_expr.original_type = NULL;
-  error_expr.value = error_mark_node;
+  error_expr.set_error ();
   matched_assoc.type_location = UNKNOWN_LOCATION;
   matched_assoc.type = NULL_TREE;
   matched_assoc.expression = error_expr;
@@ -7505,13 +7505,13 @@ c_parser_postfix_expression (c_parser *parser)
 	    gcc_assert (c_dialect_objc ());
 	    if (!c_parser_require (parser, CPP_DOT, "expected %<.%>"))
 	      {
-		expr.value = error_mark_node;
+		expr.set_error ();
 		break;
 	      }
 	    if (c_parser_next_token_is_not (parser, CPP_NAME))
 	      {
 		c_parser_error (parser, "expected identifier");
-		expr.value = error_mark_node;
+		expr.set_error ();
 		break;
 	      }
 	    c_token *component_tok = c_parser_peek_token (parser);
@@ -7525,7 +7525,7 @@ c_parser_postfix_expression (c_parser *parser)
 	  }
 	default:
 	  c_parser_error (parser, "expected expression");
-	  expr.value = error_mark_node;
+	  expr.set_error ();
 	  break;
 	}
       break;
@@ -7547,7 +7547,7 @@ c_parser_postfix_expression (c_parser *parser)
 	      parser->error = true;
 	      c_parser_skip_until_found (parser, CPP_CLOSE_BRACE, NULL);
 	      c_parser_skip_until_found (parser, CPP_CLOSE_PAREN, NULL);
-	      expr.value = error_mark_node;
+	      expr.set_error ();
 	      break;
 	    }
 	  stmt = c_begin_stmt_expr ();
@@ -7576,7 +7576,7 @@ c_parser_postfix_expression (c_parser *parser)
 				     "expected %<)%>");
 	  if (type_name == NULL)
 	    {
-	      expr.value = error_mark_node;
+	      expr.set_error ();
 	    }
 	  else
 	    expr = c_parser_postfix_expression_after_paren_type (parser,
@@ -7636,7 +7636,7 @@ c_parser_postfix_expression (c_parser *parser)
 	    c_parser_consume_token (parser);
 	    if (!c_parser_require (parser, CPP_OPEN_PAREN, "expected %<(%>"))
 	      {
-		expr.value = error_mark_node;
+		expr.set_error ();
 		break;
 	      }
 	    e1 = c_parser_expr_no_commas (parser, NULL);
@@ -7645,7 +7645,7 @@ c_parser_postfix_expression (c_parser *parser)
 	    if (!c_parser_require (parser, CPP_COMMA, "expected %<,%>"))
 	      {
 		c_parser_skip_until_found (parser, CPP_CLOSE_PAREN, NULL);
-		expr.value = error_mark_node;
+		expr.set_error ();
 		break;
 	      }
 	    loc = c_parser_peek_token (parser)->location;
@@ -7655,7 +7655,7 @@ c_parser_postfix_expression (c_parser *parser)
 				       "expected %<)%>");
 	    if (t1 == NULL)
 	      {
-		expr.value = error_mark_node;
+		expr.set_error ();
 	      }
 	    else
 	      {
@@ -7677,7 +7677,7 @@ c_parser_postfix_expression (c_parser *parser)
 	  c_parser_consume_token (parser);
 	  if (!c_parser_require (parser, CPP_OPEN_PAREN, "expected %<(%>"))
 	    {
-	      expr.value = error_mark_node;
+	      expr.set_error ();
 	      break;
 	    }
 	  t1 = c_parser_type_name (parser);
@@ -7688,7 +7688,7 @@ c_parser_postfix_expression (c_parser *parser)
 	  if (parser->error)
 	    {
 	      c_parser_skip_until_found (parser, CPP_CLOSE_PAREN, NULL);
-	      expr.value = error_mark_node;
+	      expr.set_error ();
 	      break;
 	    }
 
@@ -7777,7 +7777,7 @@ c_parser_postfix_expression (c_parser *parser)
 					    &cexpr_list, true,
 					    &close_paren_loc))
 	      {
-		expr.value = error_mark_node;
+		expr.set_error ();
 		break;
 	      }
 
@@ -7785,7 +7785,7 @@ c_parser_postfix_expression (c_parser *parser)
 	      {
 		error_at (loc, "wrong number of arguments to "
 			       "%<__builtin_choose_expr%>");
-		expr.value = error_mark_node;
+		expr.set_error ();
 		break;
 	      }
 
@@ -7810,25 +7810,25 @@ c_parser_postfix_expression (c_parser *parser)
 	  c_parser_consume_token (parser);
 	  if (!c_parser_require (parser, CPP_OPEN_PAREN, "expected %<(%>"))
 	    {
-	      expr.value = error_mark_node;
+	      expr.set_error ();
 	      break;
 	    }
 	  t1 = c_parser_type_name (parser);
 	  if (t1 == NULL)
 	    {
-	      expr.value = error_mark_node;
+	      expr.set_error ();
 	      break;
 	    }
 	  if (!c_parser_require (parser, CPP_COMMA, "expected %<,%>"))
 	    {
 	      c_parser_skip_until_found (parser, CPP_CLOSE_PAREN, NULL);
-	      expr.value = error_mark_node;
+	      expr.set_error ();
 	      break;
 	    }
 	  t2 = c_parser_type_name (parser);
 	  if (t2 == NULL)
 	    {
-	      expr.value = error_mark_node;
+	      expr.set_error ();
 	      break;
 	    }
 	  {
@@ -7840,7 +7840,7 @@ c_parser_postfix_expression (c_parser *parser)
 	    e2 = groktypename (t2, NULL, NULL);
 	    if (e1 == error_mark_node || e2 == error_mark_node)
 	      {
-		expr.value = error_mark_node;
+		expr.set_error ();
 		break;
 	      }
 
@@ -7865,14 +7865,14 @@ c_parser_postfix_expression (c_parser *parser)
 					    &cexpr_list, false,
 					    &close_paren_loc))
 	      {
-		expr.value = error_mark_node;
+		expr.set_error ();
 		break;
 	      }
 	    if (vec_safe_length (cexpr_list) != 2)
 	      {
 		error_at (loc, "wrong number of arguments to "
 			       "%<__builtin_call_with_static_chain%>");
-		expr.value = error_mark_node;
+		expr.set_error ();
 		break;
 	      }
 
@@ -7907,7 +7907,7 @@ c_parser_postfix_expression (c_parser *parser)
 					    &cexpr_list, false,
 					    &close_paren_loc))
 	      {
-		expr.value = error_mark_node;
+		expr.set_error ();
 		break;
 	      }
 
@@ -7915,7 +7915,7 @@ c_parser_postfix_expression (c_parser *parser)
 	      {
 		error_at (loc, "wrong number of arguments to "
 			       "%<__builtin_complex%>");
-		expr.value = error_mark_node;
+		expr.set_error ();
 		break;
 	      }
 
@@ -7937,7 +7937,7 @@ c_parser_postfix_expression (c_parser *parser)
 	      {
 		error_at (loc, "%<__builtin_complex%> operand "
 			  "not of real binary floating-point type");
-		expr.value = error_mark_node;
+		expr.set_error ();
 		break;
 	      }
 	    if (TYPE_MAIN_VARIANT (TREE_TYPE (e1_p->value))
@@ -7945,7 +7945,7 @@ c_parser_postfix_expression (c_parser *parser)
 	      {
 		error_at (loc,
 			  "%<__builtin_complex%> operands of different types");
-		expr.value = error_mark_node;
+		expr.set_error ();
 		break;
 	      }
 	    pedwarn_c90 (loc, OPT_Wpedantic,
@@ -7971,7 +7971,7 @@ c_parser_postfix_expression (c_parser *parser)
 					    &cexpr_list, false,
 					    &close_paren_loc))
 	      {
-		expr.value = error_mark_node;
+		expr.set_error ();
 		break;
 	      }
 
@@ -7994,7 +7994,7 @@ c_parser_postfix_expression (c_parser *parser)
 	      {
 		error_at (loc, "wrong number of arguments to "
 			       "%<__builtin_shuffle%>");
-		expr.value = error_mark_node;
+		expr.set_error ();
 	      }
 	    set_c_expr_source_range (&expr, loc, close_paren_loc);
 	    break;
@@ -8004,7 +8004,7 @@ c_parser_postfix_expression (c_parser *parser)
 	  c_parser_consume_token (parser);
 	  if (!c_parser_require (parser, CPP_OPEN_PAREN, "expected %<(%>"))
 	    {
-	      expr.value = error_mark_node;
+	      expr.set_error ();
 	      break;
 	    }
 	  {
@@ -8021,14 +8021,14 @@ c_parser_postfix_expression (c_parser *parser)
 	  c_parser_consume_token (parser);
 	  if (!c_parser_require (parser, CPP_OPEN_PAREN, "expected %<(%>"))
 	    {
-	      expr.value = error_mark_node;
+	      expr.set_error ();
 	      break;
 	    }
 	  if (c_parser_next_token_is_not (parser, CPP_NAME))
 	    {
 	      c_parser_error (parser, "expected identifier");
 	      c_parser_skip_until_found (parser, CPP_CLOSE_PAREN, NULL);
-	      expr.value = error_mark_node;
+	      expr.set_error ();
 	      break;
 	    }
 	  {
@@ -8047,13 +8047,13 @@ c_parser_postfix_expression (c_parser *parser)
 	  c_parser_consume_token (parser);
 	  if (!c_parser_require (parser, CPP_OPEN_PAREN, "expected %<(%>"))
 	    {
-	      expr.value = error_mark_node;
+	      expr.set_error ();
 	      break;
 	    }
 	  t1 = c_parser_type_name (parser);
 	  if (t1 == NULL)
 	    {
-	      expr.value = error_mark_node;
+	      expr.set_error ();
 	      c_parser_skip_until_found (parser, CPP_CLOSE_PAREN, NULL);
 	      break;
 	    }
@@ -8076,7 +8076,7 @@ c_parser_postfix_expression (c_parser *parser)
 	      error_at (loc, "-fcilkplus must be enabled to use "
 			"%<_Cilk_spawn%>");
 	      expr = c_parser_cast_expression (parser, NULL);
-	      expr.value = error_mark_node;
+	      expr.set_error ();
 	    }
 	  else if (c_parser_peek_token (parser)->keyword == RID_CILK_SPAWN)
 	    {
@@ -8095,7 +8095,7 @@ c_parser_postfix_expression (c_parser *parser)
 	  break;
 	default:
 	  c_parser_error (parser, "expected expression");
-	  expr.value = error_mark_node;
+	  expr.set_error ();
 	  break;
 	}
       break;
@@ -8116,7 +8116,7 @@ c_parser_postfix_expression (c_parser *parser)
       /* Else fall through to report error.  */
     default:
       c_parser_error (parser, "expected expression");
-      expr.value = error_mark_node;
+      expr.set_error ();
       break;
     }
   return c_parser_postfix_expression_after_primary
@@ -8331,7 +8331,7 @@ c_parser_postfix_expression_after_primary (c_parser *parser,
 	  else
 	    {
 	      c_parser_error (parser, "expected identifier");
-	      expr.value = error_mark_node;
+	      expr.set_error ();
 	      expr.original_code = ERROR_MARK;
               expr.original_type = NULL;
 	      return expr;
@@ -8363,7 +8363,7 @@ c_parser_postfix_expression_after_primary (c_parser *parser,
 	  else
 	    {
 	      c_parser_error (parser, "expected identifier");
-	      expr.value = error_mark_node;
+	      expr.set_error ();
 	      expr.original_code = ERROR_MARK;
 	      expr.original_type = NULL;
 	      return expr;
diff --git a/gcc/c/c-tree.h b/gcc/c/c-tree.h
index 4a0236d87a9..444e9a4777e 100644
--- a/gcc/c/c-tree.h
+++ b/gcc/c/c-tree.h
@@ -143,6 +143,15 @@ struct c_expr
      of this expression.  */
   location_t get_start () const { return src_range.m_start; }
   location_t get_finish () const { return src_range.m_finish; }
+
+  /* Set the value to error_mark_node whilst ensuring that src_range
+     is initialized.  */
+  void set_error ()
+  {
+    value = error_mark_node;
+    src_range.m_start = UNKNOWN_LOCATION;
+    src_range.m_finish = UNKNOWN_LOCATION;
+  }
 };
 
 /* Type alias for struct c_expr. This allows to use the structure
diff --git a/gcc/c/c-typeck.c b/gcc/c/c-typeck.c
index 8297aae4bd8..30102404284 100644
--- a/gcc/c/c-typeck.c
+++ b/gcc/c/c-typeck.c
@@ -3533,7 +3533,12 @@ parser_build_binary_op (location_t location, enum tree_code code,
   result.original_type = NULL;
 
   if (TREE_CODE (result.value) == ERROR_MARK)
-    return result;
+    {
+      set_c_expr_source_range (&result,
+			       arg1.get_start (),
+			       arg2.get_finish ());
+      return result;
+    }
 
   if (location != UNKNOWN_LOCATION)
     protected_set_expr_location (result.value, location);