Additional FreeBSD fixes (#865)

Add FreeBSD support for swift-testing.

### Result:
With this PR, swift-testing can be built on FreeBSD (tested on x86_64
FreeBSD 14.1-RELEASE-p6)

### Known issue:
There are some issue running `swift test` on this repo, but most likely
due to bugs in my host toolchain.
- Tests failed to link due to duplicated main symbols:
```
error: link command failed with exit code 1 (use -v to see invocation)
ld: error: duplicate symbol: main
>>> defined at TestingMacrosMain.swift:0 (/zdata/swift-main/swift-project/swift-testing/Sources/TestingMacros/TestingMacrosMain.swift:0)
>>>            /zdata/swift-main/swift-project/swift-testing/.build/x86_64-unknown-freebsd14.1/debug/TestingMacros-tool.build/TestingMacrosMain.swift.o:(main)
>>> defined at runner.swift:0 (/zdata/swift-main/swift-project/swift-testing/.build/x86_64-unknown-freebsd14.1/debug/swift-testingPackageTests.derived/runner.swift:0)
>>>            /zdata/swift-main/swift-project/swift-testing/.build/x86_64-unknown-freebsd14.1/debug/swift_testingPackageTests-tool.build/runner.swift.o:(.text.main+0x0)
clang: error: linker command failed with exit code 1 (use -v to see invocation)
[25/26] Linking swift-testingPackageTests.xctest
```

- [x] Code and documentation should follow the style of the [Style
Guide](https://github.com/apple/swift-testing/blob/main/Documentation/StyleGuide.md).
- [x] If public symbols are renamed or modified, DocC references should
be updated.

Sources/Testing/ExitTests/ExitTest.swift

@@ -114,7 +114,7 @@ extension ExitTest {
     // As with Linux, disable the generation core files. FreeBSD does not, as
     // far as I can tell, special-case RLIMIT_CORE=1.
     var rl = rlimit(rlim_cur: 0, rlim_max: 0)
-    _ = setrlimit(CInt(RLIMIT_CORE.rawValue), &rl)
+    _ = setrlimit(RLIMIT_CORE, &rl)
 #elseif os(Windows)
     // On Windows, similarly disable Windows Error Reporting and the Windows
     // Error Reporting UI. Note we expect to be the first component to call

Sources/Testing/ExitTests/SpawnProcess.swift

@@ -143,12 +143,19 @@ func spawnExecutable(
 #if SWT_TARGET_OS_APPLE
       // Close all other file descriptors open in the parent.
       flags |= CShort(POSIX_SPAWN_CLOEXEC_DEFAULT)
-#elseif os(Linux) || os(FreeBSD)
+#elseif os(Linux)
       // This platform doesn't have POSIX_SPAWN_CLOEXEC_DEFAULT, but we can at
       // least close all file descriptors higher than the highest inherited one.
       // We are assuming here that the caller didn't set FD_CLOEXEC on any of
       // these file descriptors.
       _ = swt_posix_spawn_file_actions_addclosefrom_np(fileActions, highestFD + 1)
+#elseif os(FreeBSD)
+      // Like Linux, this platfrom doesn't have POSIX_SPAWN_CLOEXEC_DEFAULT;
+      // However; unlike Linux, all non-EOL FreeBSD (>= 13.1) supports
+      // `posix_spawn_file_actions_addclosefrom_np` and therefore we don't need
+      // need `swt_posix_spawn_file_actions_addclosefrom_np` to guard the availability
+      // of this api.
+      _ = posix_spawn_file_actions_addclosefrom_np(fileActions, highestFD + 1)
 #else
 #warning("Platform-specific implementation missing: cannot close unused file descriptors")
 #endif

Sources/Testing/ExitTests/WaitFor.swift

@@ -85,7 +85,11 @@ private let _childProcessContinuations = Locked<[pid_t: CheckedContinuation<Exit
 /// A condition variable used to suspend the waiter thread created by
 /// `_createWaitThread()` when there are no child processes to await.
 private nonisolated(unsafe) let _waitThreadNoChildrenCondition = {
+  #if os(FreeBSD)
+  let result = UnsafeMutablePointer<pthread_cond_t?>.allocate(capacity: 1)
+  #else
   let result = UnsafeMutablePointer<pthread_cond_t>.allocate(capacity: 1)
+  #endif
   _ = pthread_cond_init(result, nil)
   return result
 }()
@@ -132,7 +136,7 @@ private let _createWaitThread: Void = {
 
   // Create the thread. It will run immediately; because it runs in an infinite
   // loop, we aren't worried about detaching or joining it.
-#if SWT_TARGET_OS_APPLE
+#if SWT_TARGET_OS_APPLE || os(FreeBSD)
   var thread: pthread_t?
 #else
   var thread = pthread_t()

Sources/Testing/Support/Locked.swift

@@ -36,20 +36,22 @@ struct Locked<T>: RawRepresentable, Sendable where T: Sendable {
   /// To keep the implementation of this type as simple as possible,
   /// `pthread_mutex_t` is used on Apple platforms instead of `os_unfair_lock`
   /// or `OSAllocatedUnfairLock`.
-#if SWT_TARGET_OS_APPLE || os(Linux) || os(FreeBSD) || os(Android) || (os(WASI) && compiler(>=6.1) && _runtime(_multithreaded))
-  private typealias _Lock = pthread_mutex_t
+#if SWT_TARGET_OS_APPLE || os(Linux) || os(Android) || (os(WASI) && compiler(>=6.1) && _runtime(_multithreaded))
+  typealias PlatformLock = pthread_mutex_t
+#elseif os(FreeBSD)
+  typealias PlatformLock = pthread_mutex_t?
 #elseif os(Windows)
-  private typealias _Lock = SRWLOCK
+  typealias PlatformLock = SRWLOCK
 #elseif os(WASI)
   // No locks on WASI without multithreaded runtime.
-  private typealias _Lock = Void
+  typealias PlatformLock = Void
 #else
 #warning("Platform-specific implementation missing: locking unavailable")
-  private typealias _Lock = Void
+  typealias PlatformLock = Void
 #endif
 
   /// A type providing heap-allocated storage for an instance of ``Locked``.
-  private final class _Storage: ManagedBuffer<T, _Lock> {
+  private final class _Storage: ManagedBuffer<T, PlatformLock> {
     deinit {
       withUnsafeMutablePointerToElements { lock in
 #if SWT_TARGET_OS_APPLE || os(Linux) || os(FreeBSD) || os(Android) || (os(WASI) && compiler(>=6.1) && _runtime(_multithreaded))
@@ -66,7 +68,7 @@ struct Locked<T>: RawRepresentable, Sendable where T: Sendable {
   }
 
   /// Storage for the underlying lock and wrapped value.
-  private nonisolated(unsafe) var _storage: ManagedBuffer<T, _Lock>
+  private nonisolated(unsafe) var _storage: ManagedBuffer<T, PlatformLock>
 
   init(rawValue: T) {
     _storage = _Storage.create(minimumCapacity: 1, makingHeaderWith: { _ in rawValue })
@@ -142,7 +144,7 @@ struct Locked<T>: RawRepresentable, Sendable where T: Sendable {
   /// - Warning: Callers that unlock the lock _must_ lock it again before the
   ///   closure returns. If the lock is not acquired when `body` returns, the
   ///   effect is undefined.
-  nonmutating func withUnsafeUnderlyingLock<R>(_ body: (UnsafeMutablePointer<pthread_mutex_t>, T) throws -> R) rethrows -> R {
+  nonmutating func withUnsafeUnderlyingLock<R>(_ body: (UnsafeMutablePointer<PlatformLock>, T) throws -> R) rethrows -> R {
     try withLock { value in
       try _storage.withUnsafeMutablePointerToElements { lock in
         try body(lock, value)

Sources/_TestingInternals/include/Includes.h

@@ -80,6 +80,10 @@
 #include <pthread.h>
 #endif
 
+#if __has_include(<pthread_np.h>)
+#include <pthread_np.h>
+#endif
+
 #if __has_include(<pty.h>)
 #include <pty.h>
 #endif
@@ -125,6 +129,10 @@
 #endif
 #endif
 
+#if defined(__FreeBSD__)
+#include <libutil.h>
+#endif
+
 #if defined(_WIN32)
 #define WIN32_LEAN_AND_MEAN
 #define NOMINMAX