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

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 Paper N4527.

   

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 the first 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 GCC nor 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 via Microsoft Connect or Send A Smile/Frown.

 

Stephan T. Lavavej

Senior Developer – Visual C++ Libraries

stl@microsoft.com