[cfe-dev] RFC: Bump toolchain requirements

[Stephen Kelly via cfe-dev]

Hi,

the policy for updating the minimum compiler versions able to build llvm 
(and as a side-effect, the option of using features of a newer C++ 
standard) is here:

  https://llvm.org/docs/DeveloperPolicy.html#toolchain

The current compiler requirements are documented here:

  https://llvm.org/docs/GettingStarted.html#host-c-toolchain

I don't know if buildbots verify those versions.

I'm wondering if anyone has strong feelings for or against bumping the 
minimum compiler requirements to:

* GCC 7.4 (Dec 2018 - https://gcc.gnu.org/gcc-7)
* Clang 6.0 (Mar 2018 - 
https://lists.llvm.org/pipermail/llvm-announce/2018-March/000077.html)
* MSVC 2019
* AppleClang ??

Those versions of GCC and Clang are available on Ubuntu 18.04 LTS.

  https://packages.ubuntu.com/bionic-updates/clang
  https://packages.ubuntu.com/bionic-updates/gcc

Ubuntu 16.04 LTS is end-of-standard-support this month:

  https://wiki.ubuntu.com/Releases

Those compilers have much-improved C++17 support compared to the current 
baseline.

Thanks,

Stephen.