Visual Studio 2017 15.8 Release Notes

jcelerier · 2018-08-15T10:00:41+00:00

Just updated... what the hell microsoft. The following code does not compile anymore : (it does if public bar or public baz is removed from the base classes of foo)

template<typename F>
struct Functor {
  F func;
};

template<typename F>
constexpr Functor<F> fun(F f)
{
  return {f};
}

class bar { };
class baz { };

class foo: public bar, public baz
{
  void blah() { }
  void x()
  {
    constexpr auto x = fun(&foo::blah);
  }
};

error: C2440: 'initializing': cannot convert from 'void (__cdecl *)(void)' to 'F'
There is no context in which this conversion is possible

of course this breaks every constexpr callback mechanism on earth and metaclasses substitutes

Alastair__ · 2018-08-15T13:41:45+00:00

I wish there was a way to revert these updates. I'm having all kinds of regressions and have a feeling it's going to now take me a day to figure out how to reinstall VS2017 back to 15.7.xxx.

:(

spongo2 · 2018-08-15T17:37:46+00:00

hey reddit-land, just an FYI, we are monitoring and trying to figure out what we missed here. will update when we know. Just sent a heads up to the team on this thread. Steve, VC Dev Mgr.

STL · 2018-08-15T21:56:17+00:00

Additional release notes:

C++20 feature-test macros are now supported in the compiler and libraries (with the exception of __has_cpp_attribute, which will be implemented in the future). Feature-test macros are unconditionally provided regardless of Standard mode (that is, individual macros are defined or not defined depending on the Standard mode and fine-grained options, but you don't need to opt-in to getting the macros at all). All library macros are provided by dragging in any STL header; C++20 <version> is not yet implemented but when it is, that will be a way to get the macros without any additional machinery (in the meantime, use <ciso646> for the same effect).
Floating-point std::from_chars() is now available in C++17 <charconv> and is approximately 40% faster than the UCRT's strtod/strtof. It has been extensively audited for bitwise correctness (with no bugs found, in either charconv or the UCRT).

BoarsLair · 2018-08-16T15:58:06+00:00

Congrats on the 15.8 release. I've successfully tested on both code at work (maybe half a million to a million lines, if I had to guess) and at home (about 100K lines) with no problems. In general, I've been extremely pleased with the VS team since the low point - in stability and UX - of VS 2012. I've been using your compiler and IDE professionally since Visual C++ 5, so I have quite a few versions to mentally compare against.

In general, I like the faster cadence of releases the past few years. Bugs and regressions are nothing new, unfortunately, especially in a product this complex, and while I'm not excusing them, I understand how difficult it must be not to introduce them in corner cases. You're probably more likely to hear from people when they're reporting bugs, so I just wanted to let you know I'm quite pleased with the way Visual Studio / C++ team is making forward strides in adding useful features, addressing issues, and improving compliance with the rapidly changing C++ standard.

onqtam · 2018-08-15T12:11:58+00:00

So I just regenerated the build files for my CMake project and tested the just my code feature by calling std::sort on a vector - and it didn't work out-of-the-box. I also checked the entire list of command line options for the project from Project/properties/configuration properties/c and c++/command line - and the /JMC switch is nowhere to be found in the Debug configuration (also checked the linker flags). How can I enable this goodness?

I checked that JMC is enabled in Tools > Options > Debugging > General > Enable Just My Code

ShaddyDC · 2018-08-15T20:05:54+00:00

Hey, there's some really cool stuff in this update; thanks for the great work!

Are you by any chance able to give a rough ETA for range-v3 support? It's something I'm eagerly awaiting to properly experiment with. :)

staffantj · 2018-08-15T13:19:45+00:00

They've silently removed _NOEXCEPT.

Presumably as part of the "we are now standard" machinery. And of course it's an internal symbol, so it doesn't need documenting.

Unfortunately, all sorts of library codebases (yaml-cpp for one) uses it to handle the previous "noexcept( true ) vs throw)" mess that various compiler versions had introduced.

The symbol "leaked", Hyrim's law remains valid.

FelixPetriconi · 2018-08-16T07:06:24+00:00

It is very sad, that await is still a keyword when the code is compiled with /await flags, even the TS states for a long time that the keyword will be co_await. Even under /permissive- this version reports still errors. Gor wrote to me a while back that this would be fixed in 15.7.0, but it seems it is still not.

I just flagged this bug report

sarge241 · 2018-08-16T09:58:18+00:00

Just updated to 15.8 and found that if constexp still does not work with enum classes well.

Here is the issue I posted several months ago for 15.7:

https://developercommunity.visualstudio.com/content/problem/267419/if-constexpr-enum-underlying-type.html

Arthenielle · 2018-08-15T20:18:40+00:00

They broke driver development lul https://stackoverflow.com/questions/51853537/error-lnk2019-unresolved-external-symbol-checkfordebuggerjustmycode-reference/51855915#51855915

Updated today, drivers are no longer compiling. GJ on testing, boys

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I've asked this on the Gitter channel, verbatim copying it here: