LibThreading: Add new detach() API to Thread

Sometimes you don't care about `joining()` the result of a thread. The
underlying pthread implementation already existed for detaching and
now we expose it to the higher level API.

Userland/Libraries/LibThreading/Thread.cpp

@@ -20,7 +20,7 @@ Threading::Thread::Thread(Function<intptr_t()> action, StringView thread_name)
 
 Threading::Thread::~Thread()
 {
- if (m_tid) {
+ if (m_tid && !m_detached) {
  dbgln("Destroying thread \"{}\"({}) while it is still running!", m_thread_name, m_tid);
  [[maybe_unused]] auto res = join();
  }
@@ -46,3 +46,13 @@ void Threading::Thread::start()
  }
  dbgln("Started thread \"{}\", tid = {}", m_thread_name, m_tid);
 }
+
+void Threading::Thread::detach()
+{
+ VERIFY(!m_detached);
+
+ int rc = pthread_detach(m_tid);
+ VERIFY(rc == 0);
+
+ m_detached = true;
+}

Userland/Libraries/LibThreading/Thread.h

@@ -1,5 +1,6 @@
 /*
  * Copyright (c) 2019-2020, Sergey Bugaev <[email protected]>
+ * Copyright (c) 2021, Spencer Dixon <[email protected]>
  *
  * SPDX-License-Identifier: BSD-2-Clause
  */
@@ -24,6 +25,7 @@ class Thread final : public Core::Object {
  virtual ~Thread();
 
  void start();
+ void detach();
 
  template<typename T = void>
  Result<T, ThreadError> join();
@@ -36,6 +38,7 @@ class Thread final : public Core::Object {
  Function<intptr_t()> m_action;
  pthread_t m_tid { 0 };
  String m_thread_name;
+ bool m_detached { false };
 };
 
 template<typename T>