{"id":10175,"date":"2016-08-24T12:38:11","date_gmt":"2016-08-24T19:38:11","guid":{"rendered":"https:\/\/blogs.msdn.microsoft.com\/vcblog\/?p=10175"},"modified":"2019-02-18T18:04:44","modified_gmt":"2019-02-18T18:04:44","slug":"c1417-features-and-stl-fixes-in-vs-15-preview-4","status":"publish","type":"post","link":"https:\/\/devblogs.microsoft.com\/cppblog\/c1417-features-and-stl-fixes-in-vs-15-preview-4\/","title":{"rendered":"C++14\/17 Features and STL Fixes in VS “15” Preview 4"},"content":{"rendered":"

Visual Studio “15” Preview 4 is now available<\/a>, with a new installer<\/a>.\u00a0 (VS “15” is an IDE version number, not a year.\u00a0 It’s the next major version after VS 2015, which was IDE version 14.\u00a0 VS has different numbers for its year branding, IDE version, and C++ compiler version.)\n<\/span><\/p>\n

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All of the features and fixes<\/a> in VS 2015 Update 3 (including optimizer improvements for std::abs(), std::min(), std::max(), and std::pow(), which we forgot to mention) are also available in VS “15” Preview 4.\u00a0 Additionally, we have something new to announce.\u00a0 Previously, new major IDE versions contained new major compiler versions and binary-incompatible STLs (which allowed us to overhaul our data structure representations for correctness and performance).\u00a0 Now that we’ve been adding features to the compiler and STL since VS 2015 RTM in a highly compatible manner, we’re going to continue this into the new major IDE version.\u00a0 Specifically, VS 2015 and VS “15” will have the same major compiler version (19) and their STLs will be binary-compatible, and this compatible compiler and STL will remain available throughout the lifecycle of VS “15”.\u00a0 This implies that the STL’s DLL will continue to be named msvcp140.dll.\u00a0 (At some point in the future, we expect to have a compiler version 20 and a binary-incompatible STL again.)\n<\/span><\/p>\n

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Note that we’re guaranteeing binary compatibility, not source compatibility.\u00a0 While the version switch<\/a> \/std:c++14 (which is the default) will typically preserve source compatibility, it is always possible for bugfixes or Issue resolutions to require source code changes.\u00a0 While we’re trying to avoid unnecessary source breaking changes, when they’re necessary they’ll be documented on MSDN, as we’ve been doing<\/a> for VS 2015 Updates.\u00a0 And note that \/std:c++latest will frequently experience source breaking changes, but we’ll try to document them too (especially in the STL, as we update our implementation to conform to the latest Working Paper, this can sometimes break source code in unexpected ways which we aren’t immediately aware of, hence the caveat).\n<\/span><\/p>\n

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To be clear, this is a good thing for you, our programmer-users.\u00a0 Although the major compiler version is remaining unchanged at 19, we’re still adding new compiler and STL features.\u00a0 (_MSC_FULL_VER will increase, allowing the updated compiler to be detected.)\u00a0 And the STL binary compatibility means that third-party libraries can be built once and used with both VS 2015 and VS “15”.\u00a0 (However, it is still best for everything to be compiled consistently with the latest available version, as that will give you the most correctness and performance.)\u00a0 Now, here’s what we’re adding:\n<\/span><\/p>\n

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Compiler Features<\/strong>\n\t\t<\/span><\/p>\n

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The C++14 feature NSDMIs for aggregates<\/a> has been implemented unconditionally by Vinny Romano.\n<\/span><\/p>\n

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The C++17 feature [[fallthrough]] attribute<\/a> has been implemented under \/std:c++latest by Shuo Chang.\n<\/span><\/p>\n

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STL Features\n<\/strong><\/span><\/p>\n

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The C++17 feature <algorithm> sample()<\/a> has been implemented under \/std:c++latest.\n<\/span><\/p>\n

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The C++17 feature is_callable<\/a> has been implemented under \/std:c++latest.\u00a0 (is_nothrow_callable was blocked by a compiler bug in Preview 4, which has been fixed for the next build.)\n<\/span><\/p>\n

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LWG Issues\n<\/strong><\/span><\/p>\n

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The following C++14 Library Issue resolutions have been implemented unconditionally:\n<\/span><\/p>\n

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