[Bug c++/65323] [4.8/4.9/5 Regression] duplicate -Wzero-as-null-pointer-constant warnings

[ktietz at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=65323

Kai Tietz <ktietz at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |ktietz at gcc dot gnu.org

--- Comment #3 from Kai Tietz <ktietz at gcc dot gnu.org> ---
Hmm, the issue seems to be that we emit within check_default_argument () two
times the call to maybe_warn_zero_as_null_pointer_constant ().  Once indirectly
via perform_implicit_conversion_flags () call, and then later on directly
within if-condition for returning nullptr_node.
It seems that second call is superflous in terms of warning.  So I suggest the
following patch:

Index: decl.c
===================================================================
--- decl.c      (Revision 221277)
+++ decl.c      (Arbeitskopie)
@@ -11231,7 +11233,8 @@ check_default_argument (tree decl, tree arg, tsub
       && TYPE_PTR_OR_PTRMEM_P (decl_type)
       && null_ptr_cst_p (arg)
       && (complain & tf_warning)
-      && maybe_warn_zero_as_null_pointer_constant (arg, input_location))
+      && c_inhibit_evaluation_warnings == 0
+      && !NULLPTR_TYPE_P(TREE_TYPE (arg)))
     return nullptr_node;

   /* [dcl.fct.default]