Add precondition guards to pthread_mutex calls (#243)

While in the current configuration lock/unlock shouldn't ever fail,
it seems polite to guard against basic misuse in debug builds.

Co-authored-by: Dan Appel <[email protected]>

Author: Danappelxx

Sources/AsyncAlgorithms/Locking.swift

@@ -37,15 +37,15 @@ internal struct Lock {
 #if canImport(Darwin)
     platformLock.initialize(to: os_unfair_lock())
 #elseif canImport(Glibc)
-    pthread_mutex_init(platformLock, nil)
+    precondition(pthread_mutex_init(platformLock, nil) == 0, "pthread_mutex_init failed")
 #elseif canImport(WinSDK)
     InitializeSRWLock(platformLock)
 #endif
   }
 
   fileprivate static func deinitialize(_ platformLock: PlatformLock) {
 #if canImport(Glibc)
-    pthread_mutex_destroy(platformLock)
+    precondition(pthread_mutex_destroy(platformLock) == 0, "pthread_mutex_destroy failed")
 #endif
     platformLock.deinitialize(count: 1)
   }
@@ -64,7 +64,7 @@ internal struct Lock {
 #if canImport(Darwin)
     os_unfair_lock_unlock(platformLock)
 #elseif canImport(Glibc)
-    pthread_mutex_unlock(platformLock)
+    precondition(pthread_mutex_unlock(platformLock) == 0, "pthread_mutex_unlock failed")
 #elseif canImport(WinSDK)
     ReleaseSRWLockExclusive(platformLock)
 #endif