A thread was started over the summer to discuss the timeline for bumping LLVM up to Visual Studio 2015 to enable the use of various new language features. Currently the ETA for this is sometime in mid-October, so within 2-3 weeks.
With this happening imminently, I thought it would be worth tossing this out there and seeing what people think.
With VS on 2015, the major lagging compiler is going to be GCC. Our minimum GCC requirement is 4.7, which is quite old (almost 4 years for anyone keeping count). What are the challenges with pushing this forward?
With VS2015, the biggest remaining missing C++14 features are variable templates, sized allocation, and extended constexpr. But it gains generic lambdas, init-captures, decltype(auto) return, and auto return without requiring the trailing → decltype syntax.
While GCC doesn’t claim to “fully” support C++14 until 5.2 (which is only about 1 year old), you can get all of the above features with GCC 4.9
So if we’re willing to allow “partial” C++14 support in LLVM (i.e a whitelisted set of features), we may be able to get many of the most useful features by going to GCC 4.9, which is still a good 2.5 years old.
One potentially added benefit of this is that GCC supports in 4.9. This might allow us to kill of llvm::Regex in favor of standardizing on std::regex, as GCC is currently the only supported compiler without a regex implementation.