Do not warn about zero-as-null when NULL is used.

gcc/cp/

Do not warn about zero-as-null when NULL is used.
* call.c (conversion_null_warnings): Check for pointer
types converted from zero constants.
(convert_like_real): Add a warning sentinel at the end.
* tree.c (maybe_warn_zero_as_null_pointer_constant): Also
check null_node_p.

testsuite/

Do not warn about zero-as-null when NULL is used.
* g++.dg/warn/Wzero-as-null-pointer-constant-7.C: New.

From-SVN: r260973

gcc/cp/ChangeLog

+2018-05-30  Ville Voutilainen  <ville.voutilainen@gmail.com>
+
+	Do not warn about zero-as-null when NULL is used.
+	* call.c (conversion_null_warnings): Check for pointer
+	types converted from zero constants.
+	(convert_like_real): Add a warning sentinel at the end.
+	* tree.c (maybe_warn_zero_as_null_pointer_constant): Also
+	check null_node_p.
+
 2018-05-24  Jason Merrill  <jason@redhat.com>
 
 	PR c++/85807 - ICE with call in template NSDMI.

gcc/cp/call.c

@@ -6517,6 +6517,7 @@ build_temp (tree expr, tree type, int flags,
 }
 
 /* Perform warnings about peculiar, but valid, conversions from/to NULL.
+   Also handle a subset of zero as null warnings.
    EXPR is implicitly converted to type TOTYPE.
    FN and ARGNUM are used for diagnostics.  */
 
@@ -6551,6 +6552,15 @@ conversion_null_warnings (tree totype, tree expr, tree fn, int argnum)
 	warning_at (input_location, OPT_Wconversion_null,
 		    "converting %<false%> to pointer type %qT", totype);
     }
+  /* Handle zero as null pointer warnings for cases other
+     than EQ_EXPR and NE_EXPR */
+  else if (null_ptr_cst_p (expr) &&
+	   (TYPE_PTR_OR_PTRMEM_P (totype) || NULLPTR_TYPE_P (totype)))
+    {
+      source_location loc =
+       expansion_point_location_if_in_system_header (input_location);
+      maybe_warn_zero_as_null_pointer_constant (expr, loc);
+    }
 }
 
 /* We gave a diagnostic during a conversion.  If this was in the second
@@ -7101,6 +7111,7 @@ convert_like_real (conversion *convs, tree expr, tree fn, int argnum,
       && !check_narrowing (totype, expr, complain))
     return error_mark_node;
 
+  warning_sentinel w (warn_zero_as_null_pointer_constant);
   if (issue_conversion_warnings)
     expr = cp_convert_and_check (totype, expr, complain);
   else

gcc/cp/tree.c

@@ -5432,7 +5432,7 @@ bool
 maybe_warn_zero_as_null_pointer_constant (tree expr, location_t loc)
 {
   if (c_inhibit_evaluation_warnings == 0
-      && !NULLPTR_TYPE_P (TREE_TYPE (expr)))
+      && !null_node_p (expr) && !NULLPTR_TYPE_P (TREE_TYPE (expr)))
     {
       warning_at (loc, OPT_Wzero_as_null_pointer_constant,
 		  "zero as null pointer constant");

gcc/testsuite/g++.dg/warn/Wzero-as-null-pointer-constant-7.C

+// { dg-options "-Wzero-as-null-pointer-constant" }
+// { dg-do compile { target c++11 } }
+
+#include <cstddef>
+
+void test01()
+{
+  char* x(NULL);
+  char* x2{NULL};
+  char* x3 = NULL;
+  char* x4(0); // { dg-warning "zero as null pointer" }
+  char* x5 = 0; // { dg-warning "zero as null pointer" }
+}