[swift-evolution] #if os(Windows) and MSVC/Cygwin Compatibility

[Joe Groff]

> On May 3, 2016, at 2:44 AM, hitstergtd+swiftevo--- via swift-evolution <swift-evolution at swift.org> wrote:
> 
> Why is there a need to support Cygwin/MingW and their variants as a
> build target for Windows? MSVC is practically free these days.

Cygwin at least is still valuable for providing a more POSIX-like environment for portability, without the Win32 interop barriers that the old NT POSIX subsystem (and presumably the new Linux syscall layer thing) have. At the language level, MSVC's C and C++ frontends are still fairly idiosyncratic compared to GCC or Clang, so I know a number of people who prefer Mingw on those grounds too.

-Joe

> Doesn't supporting multiple different ABI targets on Windows just
> complicate matters unnecessarily? Isn't MSVC enough as a build target?
> 
> I am not dejecting; rather, just wondering the actual need.
> 
> On 3 May 2016 at 06:00, Sangjin Han via swift-evolution
> <swift-evolution at swift.org> wrote:
>> Hello swift-evolution,
>> 
>> This is continued from PR #2351(https://github.com/apple/swift/pull/2351).
>> 
>> Here is the brief history. (To avoid confusion, I used MSVC refer to
>> *-*-windows-msvc and Cygwin refer to *-*-windows-cygnus in LLVM.)
>> 
>> I needed the #if method to distinct MSVC from Cygwin, for mapping the Int to
>> CLongLong not CLong on MSVC.
>> In PR #2351, I simply added 'os(Cygwin)' and restrict 'os(Windows)' to
>> *-*-windows-msvc from *-*-windows-*, this solved my problem.
>> 
>> Jake(@jakepetroules) pointed out that Cygwin is not an OS and it will never
>> fixed to avoid breaking user applications.
>> There is more  participants and opinions, briefly,
>> - introduce another new one such as 'env(cygnus)' or 'triple(Cygwin)'
>> - the usability of the common condition 'os(Windows)' for *-*-windows-*
>> - fundamentally, what do we gain from asking which os() is in use?
>> - 'env()' is too vague
>> - what the right questions?
>> 
>> Forgive me the poor quotations of valuable opinions.
>> 
>> 
>> I hope we find out the solution or method everybody satisfied.
>> 
>> 
>> -Han Sangjin
>> 
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