Swift on Windows without Visual Studio?

[compnerd (Saleem Abdulrasool)]

@ksluder

I am thoroughly confused as to how this can be possible. ucrt ships via Windows Update. Apps that are written in C++ and target recent versions of Windows can ship without a VCRedist. They’ll link the ucrt at launch, and the statically linked VCRuntime in the app will resolve imports found in ucrt. Are you saying that ucrt also imports symbols provided by ucrt? I would characterize that as an ABI rather than a dependency. A more typical (IMO) ABI would only have VCRedist import from ucrt, and use runtime callback registration to implement the other direction.

The redistributable isn't the issue, the headers and import libraries are. msvcprt headers, SAL, atomics, vcruntime.h, etc are all provided through the MSVC ToolSet. This also includes the low level C headers (e.g. stdint.h). The import libraries vcruntime.lib, msvcrt.lib, etc are part of the "vcruntime", which is part of the toolset.

vcruntime does not call into ucrt, ucrt calls into vcruntime. You don't statically link in vcruntime and dynamically link in ucrt. I'm not sure I see how this is ABI and not a dependency.