fix: Fix NIOCore build for wasm targets

[scottmarchant]

Fixes NIOCore compiler errors for the wasm32 architecture.

Motivation:

When compiling NIOCore for a Swift WebAssembly target, several compilation errors such as the following occur:

> swift build --swift-sdk wasm32-unknown-wasi --target NIOCore

.../swift-nio/Sources/NIOCore/FileHandle.swift:151:42: error: cannot find type 'TwoUInt32s' in scope
149 | public final class NIOFileHandle: FileDescriptor & Sendable {
150 |     private static let descriptorClosed: CInt = CInt.min
151 |     private let descriptor: UnsafeAtomic<TwoUInt32s>
    |                                          `- error: cannot find type 'TwoUInt32s' in scope
152 | 
153 |     public var isOpen: Bool {
.../swift-nio/Sources/NIOCore/FileHandle.swift:77:8: error: Unknown architecture
 75 | typealias TwoUInt32s = DoubleWord
 76 | #else
 77 | #error("Unknown architecture")
    |        `- error: Unknown architecture
 78 | #endif
 79 | 
 
…

The compilation errors were introduced with the following change:

https://github.com/apple/swift-nio/pull/2598/files#diff-a041d0c0d50a8f4fcda2020eeb4450ea994920ef61653cc06014457ccdb3ba0cR70

Modifications:

The fix is straight-forward and unlikely to affect any existing compilation targets other than the wasm32 target.

We simply need to add arch(wasm32) to compiler architecture condtions for a new typedef on line, then NIOCore compiles to wasm32 again.

Result:

Before: NIOCore wasm build fails ❌

After: NIOCore wasm build succeeds ✅

[scottmarchant]

cc @MaxDesiatov @kateinoigakukun

[weissi]

Amazing, thanks so much and sorry for missing wasm!

[kateinoigakukun]

If this only matters the pointer size, _pointerBitWidth(_64) and _pointerBitWidth(_32) might be better choice

[MaxDesiatov]

+1, otherwise it misses plenty of other 32-bit architectures that in theory could be supported in the future.

[weissi]

That's up to the NIO folks but

• _pointerBitWidth* is underscored and we have non-underscored alternatives (but yes, they're annoying)
• mixed platforms like arm64_32 need to fall into the correct place, which in this case would be true (assuming that _pointerBitWidth(_32) is true for arm64_32

[glbrntt]

My gut feeling is to avoid the underscored APIs. If it becomes necessary to support more 32-bit architectures in the future then we should push to get a non-underscored API.

[scottmarchant]

Sounds like the consensus is stick with || arch(wasm32). I'll leave as-is unless someone voice opinions otherwise. Happy to change this if desired, though.

I tried out adding || _pointerBitWidth(_32) instead of || arch(wasm32), and that also worked, just as a data point.

[weissi]

Friendly ping @glbrntt to approve & merge

[scottmarchant]

Amazing, thanks so much and sorry for missing wasm!

@weissi No worries at all - pretty hard to catch them all. I meant to mention, I was impressed with that nice #error("Unknown architecture") fail mode. Pointed me straight to the right spot and helped me figure out what to do.

[glbrntt]

Thank you!

[kateinoigakukun]

FWIW I just opened a PR to set up CI for Wasm SDK #3159