[v3 PATCH] Implement LWG 2221, No formatted output operator for nullptr

[Jonathan Wakely]

On 03/12/17 23:08 +0200, Ville Voutilainen wrote:
>Tested on Linux-x64.
>
>2017-11-14  Ville Voutilainen  <ville.voutilainen@gmail.com>
>
>    Implement LWG 2221
>    * include/std/ostream (operator<<(nullptr_t)): New.
>    * testsuite/27_io/basic_ostream/inserters_other/char/lwg2221.cc: New.

>diff --git a/libstdc++-v3/include/std/ostream b/libstdc++-v3/include/std/ostream
>index f7cab03..18011bc 100644
>--- a/libstdc++-v3/include/std/ostream
>+++ b/libstdc++-v3/include/std/ostream
>@@ -245,6 +245,12 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
>       operator<<(const void* __p)
>       { return _M_insert(__p); }
>
>+#if __cplusplus > 201402L
>+      __ostream_type&
>+      operator<<(nullptr_t)
>+      { return *this << "nullptr"; }
>+#endif

As discussed on IRC, this requires a new symbol to be exported for the
std::ostream and std::wostream explicit instantiations, or the new
test will fail to link at -O0.

That should wait for stage 1.