From 7bf6e37fc44595f9015bb08a6bac18abb987cbbd Mon Sep 17 00:00:00 2001
From: "Aryan Singh K." <70511529+aryansk@users.noreply.github.com>
Date: Tue, 11 Aug 2026 15:03:44 +0530
Subject: [PATCH] fix(wasi): use mock TLS for all non-threaded WASI targets

The gate os(WASI) && (swift(<6.1) || !_runtime) incorrectly falls
through to pthread APIs on Swift 6.1+ non-threaded WASI, where
pthread_* is not in scope. Guard solely on !_runtime.

Fixes #370
---
 Sources/System/Internals/Exports.swift | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/Sources/System/Internals/Exports.swift b/Sources/System/Internals/Exports.swift
index 088a3251..6ce7d4dc 100644
--- a/Sources/System/Internals/Exports.swift
+++ b/Sources/System/Internals/Exports.swift
@@ -184,7 +184,7 @@ extension String {
 // TLS
 #if os(Windows)
 internal typealias _PlatformTLSKey = DWORD
-#elseif os(WASI) && (swift(<6.1) || !_runtime(_multithreaded))
+#elseif os(WASI) && !_runtime(_multithreaded)
 // Mock TLS storage for single-threaded WASI.
 // Carries no state of its own, and only used to index `sharedTLSStorage`.
 internal final class _PlatformTLSKey: @unchecked Sendable {
@@ -214,7 +214,7 @@ internal func makeTLSKey() -> _PlatformTLSKey {
     fatalError("Unable to create key")
   }
   return raw
-  #elseif os(WASI) && (swift(<6.1) || !_runtime(_multithreaded))
+  #elseif os(WASI) && !_runtime(_multithreaded)
   return _PlatformTLSKey()
   #else
   var raw = pthread_key_t()