C++11/14/17 Features In VS 2015 RTM

Stephan T. Lavavej - MSFT

19 Jun 2015 11:47 AM
//z 2015-07-15 08:49:04 L.169'54656 BG57IV3@BYH T3824780732.K.F2506529148[T10,L352,R14,V142]

We're still working on finishing VS 2015 RTM, but we're definitely done with adding new features, so we can publish final feature tables.  Let's start with the STL, where we implemented a bunch of stuff after publishing 2015 RC's features in April.  Whenever I mention C++17 below, I'm referring to the current Working PaperN4527.

  //z 2015-07-15 08:49:04 L.169'54656 BG57IV3@BYH T3824780732.K.F2506529148[T10,L352,R14,V142]

Standard Library

  

This table of C++14/17 Library features contains new rows for the features that were voted into C++17 in May:

  

Status	Std	Paper	Title
missing	C++14	N3462	SFINAE-Friendly result_of
missing	C++17	N4387	Improving pair And tuple
missing	C++17	N4508	shared_mutex (Untimed)
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

  

"2015 opt-in" means that this is guarded by a macro.  By default, we provide auto_ptr/etc.  If you define _HAS_AUTO_PTR_ETC to 0 project-wide (which you should do via the command line or project file, not via #define), then we won't provide auto_ptr/etc.  In the next major version, I'm planning to make this opt-out, and in the major version after that, I'm planning to eliminate auto_ptr/etc. entirely.  Now would be a good time to start migrating your code.

  

"N/A" means that these proposals altered the Standard's wording, but did not physically affect implementers or users.  I've listed them as Not Applicable for the sake of completeness.

  

Here's a detailed summary of our status:

  

Our C99 Standard Library implementation is complete, except for tgmath.h (which is irrelevant in C++) and the CX_LIMITED_RANGE/FP_CONTRACT pragma macros.

  

On top of that, our C++11 Standard Library implementation is complete.

  

On top of that, our C++14 Standard Library implementation is complete, except for Expression SFINAE in result_of (N3462) and std::function (LWG 2132), plus 11 more Library Issues.

  

On top of that, our C++17-so-far Standard Library implementation is complete, except for pair/tuple improvements (N4387) and untimed shared_mutex (N4508), plus 10 Library Issues.

  

Any remaining exceptions are bugs.  (By the way, we've fixed roughly 160 bugs in the STL between 2013 and 2015.  A year ago, I listed thefirst batch of fixes.  I'll write about the rest of the fixes soon.)  For example, we've implemented every occurrence of constexpr in C++17-so-far's STL, with a very small number of exceptions, which are tracked by DevDiv#1184873/Connect#1414341 and DevDiv#1188232:

  

• (C99) offsetof
• (C++11) numeric_limits<float/double/long double>::quiet_NaN()/signaling_NaN()
• (C++11) mutex's default constructor
• (C++14) error_category's default constructor
• (C++14) min()/max()/minmax() for initializer_list
• (C++17) min_element()/max_element()/minmax_element()

  

We've been focused on achieving Standard conformance, which is higher priority than implementing the various Technical Specifications that are being produced by the Committee.  (We think TSes are important, but the Standard is even more important.)  However, we've implemented a couple of TS things: the Filesystem "V3" TS (N4100) and Uniform Container Erasure (N4529 [container.erasure]).

  

Core Language

  

C++11 Core Language Features	VS 2013	VS 2015	Notes
Rvalue references	Partial	Yes
ref-qualifiers	No	Yes
Non-static data member initializers	Partial	Yes
Variadic templates	Yes	Yes
Initializer lists	Partial	Yes
static_assert	Yes	Yes
auto	Yes	Yes
Trailing return types	Yes	Yes
Lambdas	Yes	Yes
decltype	Yes	Yes
Right angle brackets	Yes	Yes
Default template args for function templates	Yes	Yes
Expression SFINAE	No	No	[1]
Alias templates	Yes	Yes
Extern templates	Yes	Yes
nullptr	Yes	Yes
Strongly typed enums	Yes	Yes
Forward declared enums	Yes	Yes
Attributes	No	Yes	[RTM]
constexpr	No	Yes	[RTM]
Alignment	Partial	Yes
Delegating constructors	Yes	Yes
Inheriting constructors	No	Yes
Explicit conversion operators	Yes	Yes
char16_t and char32_t	No	Yes
Unicode string literals	No	Yes
Raw string literals	Yes	Yes
Universal character names in literals	No	Yes
User-defined literals	No	Yes
Standard-layout and trivial types	Yes	Yes
Defaulted and deleted functions	Partial	Yes
Extended friend declarations	Yes	Yes
Extended sizeof	No	Yes
Inline namespaces	No	Yes
Unrestricted unions	No	Yes
Local and unnamed types as template args	Yes	Yes
Range-based for-loop	Yes	Yes
override and final	Yes	Yes
Minimal GC support	Yes	Yes
noexcept	No	Yes
C++11 Core Language Features: Concurrency	VS 2013	VS 2015	Notes
Reworded sequence points	Yes	Yes
Atomics	Yes	Yes
Strong compare and exchange	Yes	Yes
Bidirectional fences	Yes	Yes
Memory model	Yes	Yes
Data-dependency ordering	Yes	Yes
Data-dependency ordering: attributes	No	Yes	[RTM]
exception_ptr	Yes	Yes
quick_exit and at_quick_exit	No	Yes
Atomics in signal handlers	Yes	Yes
Thread-local storage	Partial	Yes
Magic statics	No	Yes
C++11 Core Language Features: C99	VS 2013	VS 2015	Notes
__func__	Partial	Yes
C99 preprocessor	Partial	Partial	[2]
long long	Yes	Yes
Extended integer types	N/A	N/A	[3]
C++14 Core Language Features	VS 2013	VS 2015	Notes
Tweaked wording for contextual conversions	Yes	Yes
Binary literals	No	Yes
auto and decltype(auto) return types	No	Yes
init-captures	No	Yes
Generic lambdas	No	Yes
Variable templates	No	No
Extended constexpr	No	No
NSDMIs for aggregates	No	No
Avoiding/fusing allocations	N/A	N/A	[4]
[[deprecated]] attributes	No	Yes	[RTM]
Sized deallocation	No	Yes
Digit separators	No	Yes
C++1z (C++17?) Core Language Features	VS 2013	VS 2015	Notes
New rules for auto with braced-init-lists	No	Yes
Terse static_assert	No	No
typename in template template-parameters	No	Yes
Removing trigraphs	Yes	Yes
Nested namespace definitions	No	No
Fixing qualification conversions	No	No
Attributes for namespaces and enumerators	No	Yes	[RTM]
u8 character literals	No	Yes	[RTM]
Allowing more non-type template args	No	No
Fold expressions	No	No

  

[RTM] These features were implemented between RC and RTM.

  

[1] We're planning to start implementing Expression SFINAE in the compiler immediately after 2015 RTM, and we're planning to deliver it in an Update to 2015, supported for production use.  (But not necessarily 2015 Update 1.  It might take longer.)

  

[2] C99 preprocessor support is unchanged.  It's Partial because while the compiler supports variadic macros, our preprocessor's behavior doesn't conform to C99/C++11 in many ways.

  

[3] "Extended integer types" are listed as Not Applicable because the Standard permits but doesn't require support for types longer than long long.  We've chosen not to support such types, which is conformant behavior.  Neither GCCnor Clang has implemented such types.

  

[4] "Avoiding/fusing allocations" is listed as Not Applicable because the Standard permits but doesn't require this optimization.  We've chosen not to implement it (at least for now), which is conformant behavior.

  

A note about C++11 constexpr: this is a large feature with complicated interactions throughout the Core Language, implemented in a compiler codebase undergoing modernization, being shipped for the first time.  It contains bugs/limitations, some of which you might notice, and many of which will be fixed in Updates.  (For example, the compiler is currently unable to emit initializers for non-scalar static constexpr data members, including character arrays.  This scenario has been blocked with a warning-as-error C4579.)  Nevertheless, I've chosen to list the compiler's support for C++11 constexpr as being complete, because the STL is successfully using it, and quite intensively so.  (The STL's handful of missing constexpr occurrences are due to library-only issues, the absence of magic compiler hooks, and the absence of C++14 extended constexpr loops.)

 

Finally, we'd like to thank everyone who's reported bugs during 2015's development cycle, not just in constexpr but throughout the whole product.  If you encounter any more bugs, please report them viaMicrosoft Connect or Send A Smile/Frown.

 

Stephan T. Lavavej

Senior Developer - Visual C++ Libraries

stl@microsoft.com

//z 2015-07-15 08:49:04 L.169'54656 BG57IV3@BYH T3824780732.K.F2506529148[T10,L352,R14,V142]

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