在 VS “15” Preview 5中关于C++14/17 Features 和STL的修复

Article
10/26/2016

[原文发表地址] 在 VS “15” Preview 5中关于C++14/17 Features 和STL的修复

[原文发表时间] 2016/10/11

Visual Studio15的预览版现在可以使用了。（正如我们在之前的变更日志中所解释的那样，VS“15”是一个新的IDE版本号，而不代表年。它是在VS2015（它的IDE版本号是14）之后的下一个版本。在VS中发布的年，IDE和C++编译器都有不同的版本号。）

预览5中增加了C++14中扩展的constexpr, 并且无条件地全面支持range-for（C++17中的这个变更在C++14中已经被确定要修复），也支持C++17中的static_assert, shared_ptr::weak_type, <optional>和<variant>。我们也像往常一样修复了很多编译器和类库的缺陷，而且解决了多于10个类库的问题。

另外，VS“15”后续版本会发布对C++17中的<any>, <string_view>, apply()和make_from_tuple()的支持。它也将包含对std::vector的正确性和性能的彻底修复。当前我们仍然为了VS“15”RC的发布而工作。现在，你可以尝试访问daily toolset builds，如果发现了任何缺陷，请报告在预览5或者daily toolset builds中。

编译器功能

C++03/11 Core Language Features	VS “15”	Notes
[Everything else]	Yes	[A]
Two-phase name lookup	No
Expression SFINAE	Partial	[B]
C99 preprocessor	Partial	[C]
Extended integer types	N/A	[D]
C++14 Core Language Features	VS “15”	Notes
Avoiding/fusing allocations	N/A	[E]
Tweaked wording for contextual conversions	Yes
Binary literals	Yes
auto and decltype(auto) return types	Yes
init-captures	Yes
Generic lambdas	Yes
Variable templates	Yes
Extended constexpr	Yes	[P5]
NSDMIs for aggregates	Yes	[P4]
[[deprecated]] attribute	Yes
Sized deallocation	Yes
Digit separators	Yes
C++17 Core Language Features	VS “15”	Notes
New rules for auto with braced-init-lists	Yes
Terse static_assert	Yes	[P5] [*]
typename in template template-parameters	Yes
Removing trigraphs	Yes
Nested namespace definitions	Yes	[*]
Fixing qualification conversions	No
Attributes for namespaces and enumerators	Yes
u8 character literals	Yes
Allowing more non-type template args	No
Fold expressions	No
Removing some empty unary folds	No
Removing the register keyword	No
Removing operator++ for bool	No
Adding noexcept to the type system	No
Extended aggregate initialization	No
Capturing *this by value	No
__has_include	No
Rewording inheriting constructors	No
Direct-list-init of fixed enums from integers	No
constexpr lambdas	No
Generalized range-based for-loops	Yes	[P5]
[[fallthrough]] attribute	Yes	[P4] [*]
[[nodiscard]] attribute	No
[[maybe_unused]] attribute	No
Hexfloat literals	No
Using attribute namespaces without repetition	No
Over-aligned dynamic memory allocation	No
Template argument deduction for class templates	No
Declaring non-type template parameters with auto	No
Guaranteed copy elision	No
Replacement of class objects containing reference members	No
Refining expression evaluation order	No
Structured bindings	No
Ignoring unrecognized attributes	No
constexpr if-statements	No
Selection statements with initializers	No
Inline variables	No
Explicit default constructors and copy-list-initialization	No

[A] 我们故意忽略了在C++11中已经被弃用的C++03中的动态异常规范，并且我们没有实现它的计划，希望它以后可以从C++标准中移除。

[B] 编译器对SFINAE表达式的支持仍然在持续改进中（我们已经从VS2015的Update 2版本开始对STL有了足够的改进）,但还是不完整的。最近，我们将发布一篇博客来详细地介绍这部分功能。

[C] 关于C99 预处理的规则，目前编译器仍然是部分支持。可变的宏定义已经被支持了，但是在运行中仍然还有很多的缺陷，在标记为Yes之前我们会对它进行彻底的修复。

[D] 这个功能被标记为不适用。虽然编译器是允许的，但是很多时候是不需要支持扩展的整数类型的，比如在GCC和Clang中，所以我们选择不支持它。

[E] 这个功能同样被标记为不适用。虽然编译器是允许的，但是不需要实现这种优化。

[P4] 在VS“15”的预览版4中实现。

[P4] 在VS“15”的预览版5中实现。

[*] 这些功能通过编译选项/std:c++latest被保留。

STL Features

Status	Std	Paper	Title
missing	C++17	P0258R2	has_unique_object_representations
missing	C++17	P0063R3	C11 Standard Library
missing	C++17	P0030R1	hypot(x, y, z)
missing	C++17	P0033R1	Rewording enable_shared_from_this
…	C++17	P0220R1	Library Fundamentals V1
missing	C++17	…	<memory> shared_ptr<T[]>, shared_ptr<T[N]>
missing	C++17	P0084R2	Emplace Return Type
missing	C++17	P0083R3	Splicing Maps And Sets
missing	C++17	P0031R0	constexpr For <array> (Again) And <iterator>
missing	C++17	P0152R1	atomic::is_always_lock_free
missing	C++17	P0005R4	not_fn()
patch	C++17	P0358R1	Fixes For not_fn()
missing	C++17	P0295R0	gcd(), lcm()
missing	C++17	P0154R1	hardware_destructive_interference_size, etc.
missing	C++17	P0067R3	Elementary String Conversions
missing	C++17	…	<algorithm>/<functional> Boyer-Moore search()
patch	C++17	P0253R1	Fixing Searcher Return Types
missing	C++17	P0174R2	Deprecating Vestigial Library Parts
missing	C++17	P0302R1	Removing Allocator Support In std::function
missing	C++17	P0040R3	Extending Memory Management Tools
missing	C++17	…	<memory_resource>
patch	C++17	P0337R0	Deleting polymorphic_allocator Assignment
missing	C++17	P0024R2	Parallel Algorithms
patch	C++17	P0336R1	Renaming Parallel Execution Policies
patch	C++17	P0394R4	Parallel Algorithms Should terminate() For Exceptions
missing	C++17	P0226R1	Mathematical Special Functions
missing	C++17	P0218R1	<filesystem>
patch	C++17	P0219R1	Relative Paths For Filesystem
patch	C++17	P0392R0	Supporting string_view In Filesystem Paths
doomed	C++17	P0181R1	Ordered By Default
RC	C++17	…	<any>
RC	C++17	…	<string_view>
RC	C++17	…	<tuple> apply()
RC	C++17	P0209R2	make_from_tuple()
RC	C++17	P0254R2	Integrating string_view And std::string
Preview 5	C++17	…	<optional>
Preview 5	C++17	P0032R3	Homogeneous Interface For variant/any/optional
Preview 5	C++17	P0088R3	<variant>
Preview 5	C++17	P0163R0	shared_ptr::weak_type
Preview 5	C++17	P0307R2	Making Optional Greater Equal Again
Preview 5	C++17	P0393R3	Making Variant Greater Equal
Preview 4	C++17	…	<algorithm> sample()
Preview 4	C++17	P0077R2	is_callable, is_nothrow_callable
Update 3	C++17	P0025R1	clamp()
Update 3	C++17	P0185R1	is_swappable, is_nothrow_swappable
Update 3	C++17	P0272R1	Non-const basic_string::data()
Update 2	C++14	N3462	SFINAE-Friendly result_of
Update 2	C++17	N4387	Improving pair And tuple
Up2 Win7+	C++17	N4508	shared_mutex (Untimed)
Up2 opt-in	C++17	P0004R1	Removing Deprecated Iostreams Aliases
Update 2	C++17	P0006R0	Variable Templates For Type Traits (is_same_v, etc.)
Update 2	C++17	P0007R1	as_const()
Update 2	C++17	P0013R1	Logical Operator Type Traits (conjunction, etc.)
Update 2	C++17	P0074R0	owner_less<>
Update 2	C++17	P0092R1	<chrono> floor(), ceil(), round(), abs()
Update 2	C++17	P0156R0	Variadic lock_guard
VS 2015	C++14	N3302	constexpr For <complex>
VS 2015	C++14	N3469	constexpr For <chrono>
VS 2015	C++14	N3470	constexpr For <array>
VS 2015	C++14	N3471	constexpr For <initializer_list>, <tuple>, <utility>
VS 2015	C++14	N3545	integral_constant::operator()()
VS 2015	C++14	N3642	UDLs For <chrono>, <string> (1729ms, “meow”s, etc.)
VS 2015	C++14	N3644	Null Forward Iterators
VS 2015	C++14	N3654	quoted()
VS 2015	C++14	N3657	Heterogeneous Associative Lookup
VS 2015	C++14	N3658	integer_sequence
VS 2015	C++14	N3659	shared_mutex (Timed)
VS 2015	C++14	N3668	exchange()
VS 2015	C++14	N3669	Fixing constexpr Member Functions Without const
VS 2015	C++14	N3670	get<T>()
VS 2015	C++14	N3671	Dual-Range equal(), is_permutation(), mismatch()
VS 2015	C++14	N3778	Sized Deallocation
VS 2015	C++14	N3779	UDLs For <complex> (3.14i, etc.)
VS 2015	C++14	N3789	constexpr For <functional>
VS 2015	C++14	N3887	tuple_element_t
VS 2015	C++14	N3891	Renaming shared_mutex (Timed) To shared_timed_mutex
VS 2015	C++17	N3911	void_t
VS 2015	C++17	N4089	Safe Conversions In unique_ptr<T[]>
VS 2015	C++17	N4169	invoke()
2015 opt-in	C++17	N4190	Removing auto_ptr, random_shuffle(), And Old <functional> Stuff
VS 2015	C++17	N4258	noexcept Cleanups
VS 2015	C++17	N4259	uncaught_exceptions()
VS 2015	C++17	N4277	Trivially Copyable reference_wrapper
VS 2015	C++17	N4279	insert_or_assign()/try_emplace() For map/unordered_map
VS 2015	C++17	N4280	size(), empty(), data()
VS 2015	C++17	N4366	Precisely Constraining unique_ptr Assignment
VS 2015	C++17	N4389	bool_constant
VS 2013	C++14	N3346	Minimal Container Element Requirements
VS 2013	C++14	N3421	Transparent Operator Functors (less<>, etc.)
VS 2013	C++14	N3655	Alias Templates For <type_traits> (decay_t, etc.)
VS 2013	C++14	N3656	make_unique()
VS 2013	C++17	N4510	Supporting Incomplete Types In vector/list/forward_list
N/A	C++14	N3924	Discouraging rand()
N/A	C++17	N4284	Contiguous Iterators
N/A	C++17	P0175R1	Synopses For The C Library
N/A	C++17	P0180R2	Reserving Namespaces For Future Standardization
N/A	C++17	P0346R1	A <random> Nomenclature Tweak
N/A	C++17	P0371R1	Discouraging memory_order_consume

这张表有些复杂，我们用它来跟踪我们的工作，所以它必须有足够详细的信息告诉我们该干什么。

“…”表示在the Library Fundamentals V1 文档的位置已经被分解为一些独立的模块。

“missing”表示还没有实现，但我们正在努力实现! 尽管从一月份我们已经开始全面投入这部分功能，但是由于需要改进的模块与日俱增，所以仍有部分模块需要实现。“patch”表明这个模块将会被加入，而且关于这个模块的文档说明也需要同步更新。我们会一起实现它们，所以它们并不是真的可以为我们做一些额外的工作。（每一个patch都被分组在受到影响的功能的下面）

“doomed”表示Ordered By Default功能被发现破坏了ABI的兼容性(在其它编译器中)，所以任何供应商都不会去实现它，将会在C++17中移除。

“N/A”表示没有实现这些功能——它们在标准中有更改，但并没有为了它们的实现做任何工作，列出它们是为了让表格更加完整。

“VS 2013”表明这个模块是在很久远的编译器中被长期支持的功能。

“VS 2015”指这是在VS2015 RTM中被支持的功能。

“Update 2”和“Update 3”指VS 2015。

“Preview 4” 和“Preview 5” 指VS “15” 。

“RC”表示这些功能被提交进了VS”15”中, 但是没能及时的进入预览5中。它们在接下来的版本中被发布。

请注意，虽然我们实现了Filesystem TS（由于历史原因，我们会在<experimental/filesystem>和<filesystem>两个地方提供大家使用），我们必须在完整它的命名空间和在标准文档中标记该部分为“已经实现”之前彻底修复它。

STL在VS“15”预览5中的修复

修复了silent bad codegen对自定义分配器请求propagate_on_container_copy_assignment和propagate_on_container_move_assignment的处理。

添加了<cstdalign>。

提高了weak_ptr::lock()的性能。

修复了std::promise移动赋值操作，它之前会导致代码死锁 (VSO#243880/Connect#2972781)。

修复了编译器隐式转换atomic<T *>到T *的错误(VSO#257598)。

pointer_traits<Ptr>现在可以正确的检测Ptr::rebind<U>。

修复了move_iterator中减法操作中丢失的const限定符。

atomic<T>现在允许做operator&()重载操作(VSO#198738)。

改进了编译诊断器不正确的bind()调用(VSO#246001, reddit)。

简化了unique_ptr::operator->() (VSO#239517/Connect#2918170)。

更改了容器适配器，使它可以隐式的定义copy/move构造(VSO#234651)。

为了提高编译器的性能，STL头文件尽量避免包含一些不必要的内联编译 (VSO#221287, 这是Clang和Chromium的开发人员的需求)，这本身就有大量的代码修改。如果你的代码中假定 <vector>或者其他的STL头文件已经被嵌入到intrin.h>中，因此这些大量的头文件将会提供一些编译器内联函数的声明。遗憾的是这种假设已经被否决了。现在如果想要包含一个仅仅还有内联函数的头文件时，我们需要让sub-header 和atomic 生效。如果你遇到了编译错误，这种修复比较简单：直接包含<intrin.h> 就可以了。

Library Issues

Status	Std	Issue	Title
missing	C++17	LWG 1169	num_get not fully compatible with strto*
missing	C++17	LWG 2059	C++0x ambiguity problem with map::erase
missing	C++17	LWG 2156	Unordered containers’ reserve(n) reserves for n-1 elements
missing	C++17	LWG 2408	SFINAE-friendly common_type / iterator_traits is missing in C++14
missing	C++17	LWG 2415	Inconsistency between unique_ptr and shared_ptr
missing	C++17	LWG 2422	std::numeric_limits<T>::is_modulo description: “most machines” errata
missing	C++17	LWG 2436	Comparators for associative containers should always be CopyConstructible
missing	C++17	LWG 2724	The protected virtual member functions of memory_resource should be private
filesystem	C++17	LWG 2667	path::root_directory() description is confusing
filesystem	C++17	LWG 2669	recursive_directory_iterator effects refers to non-existent functions
filesystem	C++17	LWG 2670	system_complete refers to undefined variable ‘base’
filesystem	C++17	LWG 2671	Errors in Copy
filesystem	C++17	LWG 2673	status() effects cannot be implemented as specified
filesystem	C++17	LWG 2674	Bidirectional iterator requirement on path::iterator is very expensive
filesystem	C++17	LWG 2683	filesystem::copy() says “no effects”
filesystem	C++17	LWG 2704	recursive_directory_iterator’s members should require ‘*this is dereferenceable’
filesystem	C++17	LWG 2706	Error reporting for recursive_directory_iterator::pop() is under-specified
filesystem	C++17	LWG 2707	path construction and assignment should have “string_type&&” overloads
filesystem	C++17	LWG 2711	path is convertible from approximately everything under the sun
filesystem	C++17	LWG 2720	permissions function incorrectly specified for symlinks
filesystem	C++17	LWG 2721	remove_all has incorrect post conditions
filesystem	C++17	LWG 2723	Do directory_iterator and recursive_directory_iterator become the end iterator upon error?
filesystem	C++17	LWG 2725	filesystem::exists(const path&, error_code&) error reporting
filesystem	C++17	LWG 2726	[recursive_]directory_iterator::increment(error_code&) is underspecified
filesystem	C++17	LWG 2728	status(p).permissions() and symlink_status(p).permissions() are not specified
parallel	C++17	LWG 2687	{inclusive,exclusive}_scan misspecified
parallel	C++17	LWG 2689	Parallel versions of std::copy and std::move shouldn’t be in order
parallel	C++17	LWG 2727	Parallel algorithms with constexpr specifier
WCFB02	C++14	LWG 2140	notify_all_at_thread_exit synchronization
WCFB02	C++17	LWG 2309	mutex::lock() should not throw device_or_resource_busy
RTM	New	LWG 2769	Redundant const in the return type of any_cast(const any&)
RC	C++14	LWG 2252	Strong guarantee on vector::push_back() still broken with C++11?
RC	New	LWG 2509	[fund.ts.v2] any_cast doesn’t work with rvalue reference targets and cannot move with a value target
RC	New	LWG 2744	any’s in_place constructors
RC	New	LWG 2746	Inconsistency between requirements for emplace between optional and variant
RC	New	LWG 2754	The in_place constructors and emplace functions added by P0032R3 don’t require CopyConstructible
Preview 5	C++14	LWG 2350	min, max, and minmax should be constexpr
Preview 5	C++17	LWG 2192	Validity and return type of std::abs(0u) is unclear
Preview 5	C++17	LWG 2276	Missing requirement on std::promise::set_exception
Preview 5	C++17	LWG 2328	Rvalue stream extraction should use perfect forwarding
Preview 5	C++17	LWG 2369	constexpr max(initializer_list) vs max_element
Preview 5	C++17	LWG 2485	get() should be overloaded for const tuple&&
Preview 5	C++17	LWG 2520	N4089 broke initializing unique_ptr<T[]> from a nullptr
Preview 5	C++17	LWG 2719	permissions function should not be noexcept due to narrow contract
Preview 5	New	LWG 2713	More missing allocator-extended constructors for unordered containers
Preview 5	New	LWG 2756	C++ WP optional<T> should ‘forward’ T’s implicit conversions
Preview 4	C++14	LWG 2135	Unclear requirement for exceptions thrown in condition_variable::wait()
Preview 4	C++14	LWG 2203	scoped_allocator_adaptor uses wrong argument types for piecewise construction
Preview 4	C++14	LWG 2210	Missing allocator-extended constructor for allocator-aware containers
Preview 4	C++17	LWG 2063	Contradictory requirements for string move assignment
Preview 4	C++17	LWG 2219	INVOKE-ing a pointer to member with a reference_wrapper as the object expression
Preview 4	C++17	LWG 2439	unique_copy() sometimes can’t fall back to reading its output
Preview 4	C++17	LWG 2476	scoped_allocator_adaptor is not assignable
Preview 4	C++17	LWG 2566	Requirements on the first template parameter of container adaptors
Preview 4	C++17	LWG 2576	istream_iterator and ostream_iterator should use std::addressof
Preview 4	C++17	LWG 2577	{shared,unique}_lock should use std::addressof
Preview 4	C++17	LWG 2579	Inconsistency wrt Allocators in basic_string assignment vs. basic_string::assign
Preview 4	C++17	LWG 2583	There is no way to supply an allocator for basic_string(str, pos)
Preview 4	C++17	LWG 2586	Wrong value category used in scoped_allocator_adaptor::construct()
Preview 4	C++17	LWG 2684	priority_queue lacking comparator typedef
Preview 4	C++17	LWG 2716	Specification of shuffle and sample disallows lvalue URNGs
Update 3	C++14	LWG 2064	More noexcept issues in basic_string
Update 3	C++17	LWG 2296	std::addressof should be constexpr
Update 3	C++17	LWG 2596	vector::data() should use addressof
Update 3	C++17	LWG 2688	clamp misses preconditions and has extraneous condition on result
Update 2	C++14	LWG 2005	unordered_map::insert(T&&) protection should apply to map too
Update 2	C++14	LWG 2021	Further incorrect usages of result_of
Update 2	C++14	LWG 2132	std::function ambiguity
Update 2	C++14	LWG 2196	Specification of is_*[copy/move]_[constructible/assignable] unclear for non-referencable types
Update 2	C++17	LWG 2101	Some transformation types can produce impossible types
Update 2	C++17	LWG 2106	move_iterator wrapping iterators returning prvalues
Update 2	C++17	LWG 2127	Move-construction with raw_storage_iterator
Update 2	C++17	LWG 2217	operator==(sub_match, string) slices on embedded ‘\0’s
Update 2	C++17	LWG 2312	tuple’s constructor constraints need to be phrased more precisely
Update 2	C++17	LWG 2353	std::next is over-constrained
Update 2	C++17	LWG 2354	Unnecessary copying when inserting into maps with braced-init syntax
Update 2	C++17	LWG 2367	pair and tuple are not correctly implemented for is_constructible with no args
Up2 opt-in	C++17	LWG 2385	function::assign allocator argument doesn’t make sense
Update 2	C++17	LWG 2393	std::function’s Callable definition is broken
Update 2	C++17	LWG 2455	Allocator default construction should be allowed to throw
Update 2	C++17	LWG 2466	allocator_traits::max_size() default behavior is incorrect
Update 2	C++17	LWG 2469	Wrong specification of Requires clause of operator[] for map and unordered_map
Update 2	C++17	LWG 2549	Tuple EXPLICIT constructor templates […] will create dangling references
VS 2015	C++14	GB 9	Remove gets from C++14
VS 2015	C++14	LWG 2009	Reporting out-of-bound values on numeric string conversions
VS 2015	C++14	LWG 2078	Throw specification of async() incomplete
VS 2015	C++14	LWG 2094	duration conversion overflow shouldn’t participate in overload resolution
VS 2015	C++14	LWG 2097	packaged_task constructors should be constrained
VS 2015	C++14	LWG 2103	std::allocator_traits<std::allocator<T>>::propagate_on_container_move_assignment
VS 2015	C++14	LWG 2104	unique_lock move-assignment should not be noexcept
VS 2015	C++14	LWG 2112	User-defined classes that cannot be derived from
VS 2015	C++14	LWG 2144	Missing noexcept specification in type_index
VS 2015	C++14	LWG 2145	error_category default constructor
VS 2015	C++14	LWG 2162	allocator_traits::max_size missing noexcept
VS 2015	C++14	LWG 2174	wstring_convert::converted() should be noexcept
VS 2015	C++14	LWG 2176	Special members for wstring_convert and wbuffer_convert
VS 2015	C++14	LWG 2187	vector<bool> is missing emplace and emplace_back member functions
VS 2015	C++14	LWG 2193	Default constructors for standard library containers are explicit
VS 2015	C++14	LWG 2247	Type traits and std::nullptr_t
VS 2015	C++14	LWG 2268	Setting a default argument in the declaration of a member function assign of std::basic_string
VS 2015	C++14	LWG 2272	quoted should use char_traits::eq for character comparison
VS 2015	C++14	LWG 2275	Why is forward_as_tuple not constexpr?
VS 2015	C++14	LWG 2278	User-defined literals for Standard Library types
VS 2015	C++14	LWG 2280	begin / end for arrays should be constexpr and noexcept
VS 2015	C++14	LWG 2285	make_reverse_iterator
VS 2015	C++14	LWG 2301	Why is std::tie not constexpr?
VS 2015	C++14	LWG 2306	match_results::reference should be value_type&, not const value_type&
VS 2015	C++14	LWG 2315	weak_ptr should be movable
VS 2015	C++14	LWG 2324	Insert iterator constructors should use addressof()
VS 2015	C++14	LWG 2329	regex_match()/regex_search() with match_results should forbid temporary strings
VS 2015	C++14	LWG 2332	regex_iterator/regex_token_iterator should forbid temporary regexes
VS 2015	C++14	LWG 2339	Wording issue in nth_element
VS 2015	C++14	LWG 2344	quoted()’s interaction with padding is unclear
VS 2015	C++14	LWG 2346	integral_constant’s member functions should be marked noexcept
VS 2015	C++17	LWG 2129	User specializations of std::initializer_list
VS 2015	C++17	LWG 2133	Attitude to overloaded comma for iterators
VS 2015	C++17	LWG 2212	tuple_size for const pair request header
VS 2015	C++17	LWG 2234	assert() should allow usage in constant expressions
VS 2015	C++17	LWG 2365	Missing noexcept in shared_ptr::shared_ptr(nullptr_t)
VS 2015	C++17	LWG 2399	shared_ptr’s constructor from unique_ptr should be constrained
VS 2015	C++17	LWG 2400	shared_ptr’s get_deleter() should use addressof()
VS 2015	C++17	LWG 2401	std::function needs more noexcept
VS 2015	C++17	LWG 2403	stof() should call strtof() and wcstof()
VS 2015	C++17	LWG 2407	packaged_task(allocator_arg_t, const Allocator&, F&&) should neither be constrained nor explicit
VS 2015	C++17	LWG 2420	function<void(ArgTypes…)> does not discard the return value of the target object
VS 2015	C++17	LWG 2426	Issue about compare_exchange
VS 2015	C++17	LWG 2433	uninitialized_copy()/etc. should tolerate overloaded operator&
VS 2015	C++17	LWG 2440	seed_seq::size() should be noexcept
VS 2015	C++17	LWG 2442	call_once() shouldn’t DECAY_COPY()
VS 2015	C++17	LWG 2454	Add raw_storage_iterator::base() member
VS 2015	C++17	LWG 2458	N3778 and new library deallocation signatures
VS 2015	C++17	LWG 2464	try_emplace and insert_or_assign misspecified
VS 2015	C++17	LWG 2467	is_always_equal has slightly inconsistent default
VS 2015	C++17	LWG 2483	throw_with_nested() should use is_final
VS 2015	C++17	LWG 2484	rethrow_if_nested() is doubly unimplementable
VS 2015	C++17	LWG 2486	mem_fn() should be required to use perfect forwarding
VS 2015	C++17	LWG 2487	bind() should be const-overloaded, not cv-overloaded
VS 2015	C++17	LWG 2488	Placeholders should be allowed and encouraged to be constexpr
VS 2015	C++17	LWG 2489	mem_fn() should be noexcept
VS 2013	C++14	LWG 1214	Insufficient/inconsistent key immutability requirements for associative containers
VS 2013	C++14	LWG 2011	Unexpected output required of strings
VS 2013	C++14	LWG 2018	regex_traits::isctype Returns clause is wrong
VS 2013	C++14	LWG 2033	Preconditions of reserve, shrink_to_fit, and resize functions
VS 2013	C++14	LWG 2039	Issues with std::reverse and std::copy_if
VS 2013	C++14	LWG 2047	Incorrect “mixed” move-assignment semantics of unique_ptr
VS 2013	C++14	LWG 2049	is_destructible is underspecified
VS 2013	C++14	LWG 2050	Unordered associative containers do not use allocator_traits to define member types
VS 2013	C++14	LWG 2056	future_errc enums start with value 0 (invalid value for broken_promise)
VS 2013	C++14	LWG 2061	make_move_iterator and arrays
VS 2013	C++14	LWG 2067	packaged_task should have deleted copy c’tor with const parameter
VS 2013	C++14	LWG 2074	Off by one error in std::reverse_copy
VS 2013	C++14	LWG 2083	const-qualification on weak_ptr::owner_before
VS 2013	C++14	LWG 2087	iostream_category() and noexcept
VS 2013	C++14	LWG 2096	Incorrect constraints of future::get in regard to MoveAssignable
VS 2013	C++14	LWG 2128	Absence of global functions cbegin/cend
VS 2013	C++14	LWG 2138	atomic_flag::clear ordering constraints
VS 2013	C++14	LWG 2141	common_type trait produces reference types
VS 2013	C++14	LWG 2143	ios_base::xalloc should be thread-safe
VS 2013	C++14	LWG 2148	Hashing enums should be supported directly by std::hash
VS 2013	C++14	LWG 2188	Reverse iterator does not fully support targets that overload operator&
VS 2013	C++14	LWG 2197	Specification of is_[un]signed unclear for non-arithmetic types
VS 2013	C++14	LWG 2213	Return value of std::regex_replace
VS 2013	C++14	LWG 2229	Standard code conversion facets underspecified
VS 2013	C++14	LWG 2284	Inconsistency in allocator_traits::max_size
VS 2013	C++14	LWG 2293	Wrong facet used by num_put::do_put
VS 2013	C++14	LWG 2313	tuple_size should always derive from integral_constant
VS 2013	C++14	LWG 2317	The type property queries should be UnaryTypeTraits returning size_t
VS 2013	C++14	LWG 2330	regex(“meow”, regex::icase) is technically forbidden but should be permitted
VS 2013	C++14	LWG 2341	Inconsistency between basic_ostream::seekp(pos) and basic_ostream::seekp(off, dir)
VS 2013	C++14	LWG 2359	How does regex_constants::nosubs affect basic_regex::mark_count()?
VS 2013	C++14	LWG 2360	reverse_iterator::operator*() is unimplementable
VS 2013	C++17	LWG 2244	Issue on basic_istream::seekg
VS 2013	C++17	LWG 2273	regex_match ambiguity
VS 2013	C++17	LWG 2441	Exact-width atomic typedefs should be provided
VS 2013	C++17	LWG 2473	basic_filebuf’s relation to C FILE semantics
VS 2013	C++17	LWG 2537	Constructors for priority_queue taking allocators should call make_heap
VS 2013	C++17	LWG 2560	is_constructible underspecified when applied to a function type

即使我们已经省略了146个N/A的问题，这张表仍然很大。Library组的人员还工作在修复大量关于标准的缺陷上。

“New”代表这个问题还没有真正的被解决在C++17中，我们觉得这些问题必须在影响其他功能前被处理掉，希望将来我们实现的解决方案会被大家接受。

“RTM”表示这个问题被修复在官方发布的VS”15”中，但是并没有被及时的发布在候选版本中。

“WCFB02”代表这些问题以后会被修复在不兼容二进制的STL中（不是VS”15”中的STL）。

“filesystem”代表对于会影响<filesystem>的问题，我们会考虑合适的时候彻底的修复这些功能。

“Parallel”代表这些问题影响并行算法功能，我们还没有实现它们。

请注意：我们实现了C++14 STL的所有功能（VS2015 Update 2中的result_of SFINAE是最后一个功能）和C++14 Library的所有问题，不包括LWG 2140(由于二进制兼容问题没有被修复在VS”15”中)，在VS”15”RC中还对std::vector有彻底的修复。对于这些，我们最近会发表更详细的介绍。

这里有两个问题是值得注意的。LWG 2350 和LWG 2369在预览5中被实现，意思是在min/max/minmax(initializer_list)和min_element/max_element/minmax_element中启用了C++ 14 constexpr。然而，我们的codegen编译器(C1XX and Clang),可以编译通过这些代码，但是还不支持智能感知编译器(EDG)。我们正在修复它。

Billy Robert O’Neal III – @MalwareMinigun – bion@microsoft.com

Casey Carter – @CoderCasey – cacarter@microsoft.com

Stephan T. Lavavej – @StephanTLavavej – stl@microsoft.com

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在 VS “15” Preview 5中关于C++14/17 Features 和STL的修复

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