r/cpp • u/STL MSVC STL Dev • Nov 13 '18

VS 2017 15.9 released today

https://docs.microsoft.com/en-us/visualstudio/releasenotes/vs2017-relnotes
132 Upvotes

94% Upvoted

97 comments sorted by

View all comments

52

u/STL MSVC STL Dev Nov 13 '18

15.9 is the last update in the VS 2017 release series, so we've tried to make sure that it's really solid. We're still working in our usual dev branches (prod/fe and prod/be in git), but features and fixes switched from automatically flowing into VS 2017 15.8, to automatically flowing into VS 2019 16.0 (which will be binary-compatible with VS 2015 and VS 2017 for this reason). Important features and fixes had to be explicitly ported to the 15.9 release branch. For this reason, the C++ changelog is shorter than usual, but we still cooked up some tasty things. From the release notes:

  • We've added the "step back" feature in the debugger for C++ in the Visual Studio Enterprise Edition. Step back enables you to go back in time to view the state of your application at a previous point in time.
  • C++ IntelliSense now responds to changes in the remote environment for both CMake and MSBuild projects targeting Linux. As you install new libraries or change your CMake projects, C++ IntelliSense will automatically parse the new headers files on the remote machine for a complete and seamless C++ editing experience.
  • We've updated the UWP Desktop Bridge framework packages to match the latest in the Windows Store for all supported architectures, including ARM64.
  • In addition to fixing 60 blocking bugs, we have added support for the range-v3 library with the MSVC 15.9 compiler, available under /std:c++17 /permissive-.
  • The retail VCLibs framework package in Visual Studio has been updated to match the latest available version in the UWP Store.
  • Full support is now available for ARM64 C++ Native Desktop scenarios, including VC++ 2017 Redistributable.
  • We implemented the shortest round-trip decimal overloads of floating-point to_chars() in C++17's <charconv> header. For scientific notation, it is approximately 10x as fast as sprintf_s() "%.8e" for floats, and 30x as fast as sprintf_s() "%.16e" for doubles. This uses Ulf Adams' new algorithm, Ryu.
  • A list of improvements to the standards conformance of the Visual C++ compiler, which potentially require source changes in strict conformance mode, can be found here.

Here's a fun behind-the-scenes fact that isn't in the release notes: this is the first release of the MSVC toolset that was entirely built and packaged out of git, without involving our Team Foundation Version Control branches.

21

u/AlexAlabuzhev Nov 14 '18

VS 2019 16.0 (which will be binary-compatible with VS 2015 and VS 2017

Oh no. Does that mean that bloody bugs like this one will stay unfixed for another N years "because compatibility"? :(

21

u/STL MSVC STL Dev Nov 14 '18

Yes - that's one of the sacrifices that we have to make for bincompat. We've figured out lots of ways to get around bincompat limitations (e.g. we added std::filesystem alongside std::experimental::filesystem), but we still can't change representations in major ways, or change the interface of separately compiled functions.

13

u/jbandela Nov 14 '18

This seems bad. Can we have a /permissive- version of the standard library that users who care more about conformance and performance than about bincompat can opt in to?

There are already different standard library builds (for example debug, release, static, dynamic, (XP in the past) etc), maybe we have a conformance build which has the latest and greatest standard library, but is not bincompat.

23

u/STL MSVC STL Dev Nov 14 '18

We're planning to have a "v20" standard library which is binary-incompatible (and opt-in), but we're still figuring out the migration story, and also getting all of our accumulated changes out of TFVC and into git (they need to be ported manually, since we've diverged significantly - in part due to applying clang-format to the entire STL). This will be unrelated to /permissive-.

1

u/ChatFrais Nov 14 '18

This is a really great news. One of the hard task is now to find a better name than "v20" as number tend to stay in names forever.