diff mbox

[C++] PR 65775 ("Late-specified return type bypasses return type checks (qualified, function, array)")

Message ID d70fe42f-3918-8345-7833-6cfaa2974a73@oracle.com
State New
Headers show

Commit Message

Paolo Carlini June 25, 2017, 9:12 p.m. UTC
Hi,

in grokdeclarator the checks on the return type do nothing useful in 
case of late-specified return type because they happen too early, before 
splice_late_return_type is called. A straightforward way to solve the 
problem involves separating the checks themselves to a new 
check_function_return_type and calling it again only in case 
splice_late_return_type actually spliced the late return type (in that 
case, we should also consistently update type_quals).

As a side issue, if we want to use good and consistent locations for the 
error messages (the testcase below checks that too), we need a fall back 
to input_location for typespec_loc, because otherwise an 
UNKNOWN_LOCATION is used for the error messages of testcases like 
lambda-syntax1.C and pr60190.C.

Tested x86_64-linux.

Thanks, Paolo.

/////////////////////
/cp
2017-06-25  Paolo Carlini  <paolo.carlini@oracle.com>

	PR c++/65775
	* decl.c (check_function_return_type): New.
	(grokdeclarator): Use the latter; if declspecs->locations[ds_type_spec]
	is UNKNOWN_LOCATION fall back to input_location.

/testsuite
2017-06-25  Paolo Carlini  <paolo.carlini@oracle.com>

	PR c++/65775
	* g++.dg/cpp0x/trailing14.C: New.
diff mbox

Patch

Index: testsuite/g++.dg/cpp0x/trailing14.C
===================================================================
--- testsuite/g++.dg/cpp0x/trailing14.C	(revision 0)
+++ testsuite/g++.dg/cpp0x/trailing14.C	(working copy)
@@ -0,0 +1,15 @@ 
+// PR c++/65775
+// { dg-do compile { target c++11 } }
+// { dg-options "-Wignored-qualifiers" }
+
+using Qi = int const volatile;
+Qi q1();           // { dg-warning "1: type qualifiers ignored" }
+auto q2() -> Qi;   // { dg-warning "1: type qualifiers ignored" }
+
+using Fi = int();
+Fi f1();           // { dg-error "1: 'f1' declared as function returning a function" }
+auto f2() -> Fi;   // { dg-error "1: 'f2' declared as function returning a function" }
+
+using Ai = int[5];
+Ai a1();           // { dg-error "1: 'a1' declared as function returning an array" }
+auto a2() -> Ai;   // { dg-error "1: 'a2' declared as function returning an array" }
Index: cp/decl.c
===================================================================
--- cp/decl.c	(revision 249632)
+++ cp/decl.c	(working copy)
@@ -9789,7 +9789,43 @@  mark_inline_variable (tree decl)
     }
 }
 
+/* If TYPE has TYPE_QUALS != TYPE_UNQUALIFIED issue a warning controlled by
+   -Wignored-qualifiers and clear TYPE_QUALS to avoid cascading diagnostics.
+   If TYPE is not valid, issue an error message and return error_mark_node,
+   otherwise return TYPE itself.  */
 
+static tree
+check_function_return_type (tree type, int& type_quals,
+			    const char* name, location_t loc)
+{
+  if (type_quals != TYPE_UNQUALIFIED)
+    {
+      if (SCALAR_TYPE_P (type) || VOID_TYPE_P (type))
+	warning_at (loc, OPT_Wignored_qualifiers, "type "
+		    "qualifiers ignored on function return type");
+
+      /* We now know that the TYPE_QUALS don't apply to the
+	 decl, but to its return type.  */
+      type_quals = TYPE_UNQUALIFIED;
+    }
+
+  /* Error about some types functions can't return.  */
+
+  if (TREE_CODE (type) == FUNCTION_TYPE)
+    {
+      error_at (loc, "%qs declared as function returning a function", name);
+      return error_mark_node;
+    }
+
+  if (TREE_CODE (type) == ARRAY_TYPE)
+    {
+      error_at (loc, "%qs declared as function returning an array", name);
+      return error_mark_node;
+    }
+
+  return type;
+}
+
 /* Assign a typedef-given name to a class or enumeration type declared
    as anonymous at first.  This was split out of grokdeclarator
    because it is also used in libcc1.  */
@@ -9993,6 +10029,8 @@  grokdeclarator (const cp_declarator *declarator,
 						      declspecs->locations);
   if (typespec_loc == UNKNOWN_LOCATION)
     typespec_loc = declspecs->locations[ds_type_spec];
+  if (typespec_loc == UNKNOWN_LOCATION)
+    typespec_loc = input_location;
 
   /* Look inside a declarator for the name being declared
      and get it as a string, for an error message.  */
@@ -10828,31 +10866,10 @@  grokdeclarator (const cp_declarator *declarator,
 	    /* Declaring a function type.
 	       Make sure we have a valid type for the function to return.  */
 
-	    if (type_quals != TYPE_UNQUALIFIED)
-	      {
-		if (SCALAR_TYPE_P (type) || VOID_TYPE_P (type))
-		  {
-		    warning_at (typespec_loc, OPT_Wignored_qualifiers, "type "
-				"qualifiers ignored on function return type");
-		  }
-		/* We now know that the TYPE_QUALS don't apply to the
-		   decl, but to its return type.  */
-		type_quals = TYPE_UNQUALIFIED;
-	      }
+	    if (check_function_return_type (type, type_quals, name, typespec_loc)
+		== error_mark_node)
+	      return error_mark_node;
 
-	    /* Error about some types functions can't return.  */
-
-	    if (TREE_CODE (type) == FUNCTION_TYPE)
-	      {
-		error ("%qs declared as function returning a function", name);
-		return error_mark_node;
-	      }
-	    if (TREE_CODE (type) == ARRAY_TYPE)
-	      {
-		error ("%qs declared as function returning an array", name);
-		return error_mark_node;
-	      }
-
 	    input_location = declspecs->locations[ds_type_spec];
 	    abstract_virtuals_error (ACU_RETURN, type);
 	    input_location = saved_loc;
@@ -10959,7 +10976,17 @@  grokdeclarator (const cp_declarator *declarator,
 	      return error_mark_node;
 
 	    if (late_return_type)
-	      late_return_type_p = true;
+	      {
+		late_return_type_p = true;
+		if (type == late_return_type)
+		  {
+		    type_quals = cp_type_quals (type);
+		    if (check_function_return_type (type, type_quals,
+						    name, typespec_loc)
+			== error_mark_node)
+		      return error_mark_node;
+		  }
+	      }
 
 	    if (ctype == NULL_TREE
 		&& decl_context == FIELD