[PATCH] Do not copy std:call_once arguments (LWG 2442)

[Jonathan Wakely]

On 12/10/16 12:22 +0100, Jonathan Wakely wrote:
>This replaces the use of std::__bind_simple by direct calls to
>std::__invoke so that the arguments are not decay-copied.
>
>	* doc/xml/manual/intro.xml: Document LWG 2442 status.
>	* include/std/mutex [_GLIBCXX_HAVE_TLS] (__once_call_impl): Remove.
>	[_GLIBCXX_HAVE_TLS] (_Once_call): Declare primary template and define
>	partial specialization to unpack args and forward to std::invoke.
>	(call_once) [_GLIBCXX_HAVE_TLS]: Use forward_as_tuple and _Once_call
>	instead of __bind_simple and __once_call_impl.
>	(call_once) [!_GLIBCXX_HAVE_TLS]: Use __invoke instead of
>	__bind_simple.
>	* testsuite/30_threads/call_once/dr2442.cc: New test.
>
>Tested powerpc64le-linux, committed to trunk.

I don't know why I over-complicated it by packing and unpacking the
args in a tuple, this is much simpler, and makes the TLS and non-TLS
implementations more similar.

Tested powerpc64le-linux, committed to trunk.


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