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[PATCH] Simplify allocator usage in unordered containers

From: Jonathan Wakely <jwakely at redhat dot com>
To: libstdc++ at gcc dot gnu dot org, gcc-patches at gcc dot gnu dot org
Date: Fri, 18 Aug 2017 19:27:11 +0100
Subject: [PATCH] Simplify allocator usage in unordered containers
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While fixing PR 81891 I noticed that _Hashtable always creates a
__value_alloc_type for constructing and destroying the elements, which
is unnecessary. https://wg21.link/lwg2218 confirmed that.

We can avoid constructing new allocators just for these calls and can
call them directly on the stored allocator.

	* include/bits/hashtable_policy.h (_ReuseOrAllocNode): Remove
	__value_alloc_type and __value_alloc_traits typedefs.
	(_ReuseOrAllocNode::operator()): Call construct and destroy on the
	node allocator.
	(_Hashtable_alloc): Simplify __value_alloc_traits typedef.
	(_Hashtable_alloc<_NodeAlloc>::_M_allocate_node(_Args&&...)): Call
	construct on the node allocator.
	(_Hashtable_alloc<_NodeAlloc>::_M_deallocate_node(__node_type*)): Call
	destroy on the node allocator.

Tested powerpc64le-linux, committed to trunk.

Attachment: patch.txt
Description: Text document

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