Hi mclow.lists, danalbert,
This patch fixes ostreams operator<< so that it properly returns an lvalue
reference.
It also forces the input and return type to be basic_ostream. This is inline
with the standard.
It appears as though http://cplusplus.github.io/LWG/lwg-closed.html#1203 was
implemented even though it was never accepted (and is now closed).
http://reviews.llvm.org/D4835
Files:
include/ostream
test/input.output/iostream.format/output.streams/ostream.rvalue/return_value.pass.cpp
Index: include/ostream
===================================================================
--- include/ostream
+++ include/ostream
@@ -1044,18 +1044,13 @@
#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
-template <class _Stream, class _Tp>
+template <class _CharT, class _Traits, class _Tp>
inline _LIBCPP_INLINE_VISIBILITY
-typename enable_if
-<
- !is_lvalue_reference<_Stream>::value &&
- is_base_of<ios_base, _Stream>::value,
- _Stream&&
->::type
-operator<<(_Stream&& __os, const _Tp& __x)
+basic_ostream<_CharT, _Traits>&
+operator<<(basic_ostream<_CharT, _Traits> && __os, const _Tp& __x)
{
__os << __x;
- return _VSTD::move(__os);
+ return __os;
}
#endif // _LIBCPP_HAS_NO_RVALUE_REFERENCES
Index:
test/input.output/iostream.format/output.streams/ostream.rvalue/return_value.pass.cpp
===================================================================
--- /dev/null
+++
test/input.output/iostream.format/output.streams/ostream.rvalue/return_value.pass.cpp
@@ -0,0 +1,34 @@
+//===----------------------------------------------------------------------===//
+//
+// The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+// <ostream>
+
+// template <class charT, class traits = char_traits<charT> >
+// class basic_ostream;
+
+// template <class charT, class traits, class T>
+// basic_ostream<charT, traits>&
+// operator<<(basic_ostream<charT, traits>&& os, const T& x);
+
+#include <ostream>
+#include <type_traits>
+
+int main()
+{
+#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
+ {
+ typedef decltype(std::ostream(nullptr) << "testing...") T;
+ static_assert(std::is_same<T, std::ostream &>::value, "must be
lvalue");
+ }
+ {
+ typedef decltype(std::wostream(nullptr) << "testing...") T;
+ static_assert(std::is_same<T, std::wostream &>::value, "must be
lvalue");
+ }
+#endif // _LIBCPP_HAS_NO_RVALUE_REFERENCES
+}
Index: include/ostream
===================================================================
--- include/ostream
+++ include/ostream
@@ -1044,18 +1044,13 @@
#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
-template <class _Stream, class _Tp>
+template <class _CharT, class _Traits, class _Tp>
inline _LIBCPP_INLINE_VISIBILITY
-typename enable_if
-<
- !is_lvalue_reference<_Stream>::value &&
- is_base_of<ios_base, _Stream>::value,
- _Stream&&
->::type
-operator<<(_Stream&& __os, const _Tp& __x)
+basic_ostream<_CharT, _Traits>&
+operator<<(basic_ostream<_CharT, _Traits> && __os, const _Tp& __x)
{
__os << __x;
- return _VSTD::move(__os);
+ return __os;
}
#endif // _LIBCPP_HAS_NO_RVALUE_REFERENCES
Index: test/input.output/iostream.format/output.streams/ostream.rvalue/return_value.pass.cpp
===================================================================
--- /dev/null
+++ test/input.output/iostream.format/output.streams/ostream.rvalue/return_value.pass.cpp
@@ -0,0 +1,34 @@
+//===----------------------------------------------------------------------===//
+//
+// The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+// <ostream>
+
+// template <class charT, class traits = char_traits<charT> >
+// class basic_ostream;
+
+// template <class charT, class traits, class T>
+// basic_ostream<charT, traits>&
+// operator<<(basic_ostream<charT, traits>&& os, const T& x);
+
+#include <ostream>
+#include <type_traits>
+
+int main()
+{
+#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
+ {
+ typedef decltype(std::ostream(nullptr) << "testing...") T;
+ static_assert(std::is_same<T, std::ostream &>::value, "must be lvalue");
+ }
+ {
+ typedef decltype(std::wostream(nullptr) << "testing...") T;
+ static_assert(std::is_same<T, std::wostream &>::value, "must be lvalue");
+ }
+#endif // _LIBCPP_HAS_NO_RVALUE_REFERENCES
+}
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