Delete the old pre-c++11 Thread implementation (#7696)

Author: tgoyne

CHANGELOG.md

@@ -16,7 +16,7 @@
 -----------
 
 ### Internals
-* None.
+* `util::Thread` no longer has any functionality other than `get_name()` and `set_name()`. Use `std::thread` instead ([PR #7696](https://github.com/realm/realm-core/pull/7696)).
 
 ----------------------------------------------
 

src/realm/util/thread.cpp

@@ -16,13 +16,13 @@
  *
  **************************************************************************/
 
+#include <realm/util/thread.hpp>
+#include <realm/util/backtrace.hpp>
+
 #include <cstring>
 #include <stdexcept>
 #include <system_error>
 
-#include <realm/util/thread.hpp>
-#include <realm/util/backtrace.hpp>
-
 #if !defined _WIN32
 #include <unistd.h>
 #endif
@@ -58,25 +58,6 @@
 using namespace realm;
 using namespace realm::util;
 
-void Thread::join()
-{
-    if (!m_joinable)
-        throw util::runtime_error("Thread is not joinable");
-
-#ifdef _WIN32
-    // Returns void; error handling not possible
-    m_std_thread.join();
-#else
-    void** value_ptr = nullptr; // Ignore return value
-    int r = pthread_join(m_id, value_ptr);
-    if (REALM_UNLIKELY(r != 0))
-        join_failed(r); // Throws
-#endif
-
-    m_joinable = false;
-}
-
-
 void Thread::set_name(const std::string& name)
 {
 #if REALM_PLATFORM_APPLE
@@ -131,17 +112,6 @@ bool Thread::get_name(std::string& name) noexcept
 }
 
 
-REALM_NORETURN void Thread::create_failed(int)
-{
-    throw std::runtime_error("pthread_create() failed");
-}
-
-REALM_NORETURN void Thread::join_failed(int)
-{
-    // It is intentional that the argument is ignored here.
-    throw std::runtime_error("pthread_join() failed.");
-}
-
 void Mutex::init_as_process_shared(bool robust_if_available)
 {
 #ifdef REALM_HAVE_PTHREAD_PROCESS_SHARED

src/realm/util/thread.hpp

@@ -19,68 +19,30 @@
 #ifndef REALM_UTIL_THREAD_HPP
 #define REALM_UTIL_THREAD_HPP
 
+#include <realm/util/assert.hpp>
+#include <realm/util/features.h>
+#include <realm/util/terminate.hpp>
+
+#include <atomic>
+#include <cerrno>
+#include <cstddef>
 #include <exception>
+#include <memory>
+#include <stdexcept>
+#include <string>
 
 #ifdef _WIN32
-#include <thread>
 #include <condition_variable> // for windows non-interprocess condvars we use std::condition_variable
+#include <thread>
 #include <Windows.h>
 #include <process.h> // _getpid()
 #else
 #include <pthread.h>
 #endif
 
-// Use below line to enable a thread bug detection tool. Note: Will make program execution slower.
-// #include <../test/pthread_test.hpp>
-
-#include <cerrno>
-#include <cstddef>
-#include <string>
-
-#include <realm/util/features.h>
-#include <realm/util/assert.hpp>
-#include <realm/util/terminate.hpp>
-#include <memory>
-#include <stdexcept>
-
-#include <atomic>
-
-namespace realm {
-namespace util {
-
-
-/// A separate thread of execution.
-///
-/// This class is a C++03 compatible reproduction of a subset of std::thread
-/// from C++11 (when discounting Thread::start(), Thread::set_name(), and
-/// Thread::get_name()).
+namespace realm::util {
 class Thread {
 public:
-    Thread();
-    ~Thread() noexcept;
-
-    template <class F>
-    explicit Thread(F func);
-
-    // Disable copying. It is an error to copy this Thread class.
-    Thread(const Thread&) = delete;
-    Thread& operator=(const Thread&) = delete;
-
-    Thread(Thread&&) noexcept;
-
-    /// This method is an extension of the API provided by
-    /// std::thread. This method exists because proper move semantics
-    /// is unavailable in C++03. If move semantics had been available,
-    /// calling `start(func)` would have been equivalent to `*this =
-    /// Thread(func)`. Please see std::thread::operator=() for
-    /// details.
-    template <class F>
-    void start(F func);
-
-    bool joinable() noexcept;
-
-    void join();
-
     // If supported by the platform, set the name of the calling thread (mainly
     // for debugging purposes). The name will be silently clamped to whatever
     // limit the platform places on these names. Linux places a limit of 15
@@ -91,23 +53,6 @@ class Thread {
     // calling thread to \a name, and returns true, otherwise it does nothing
     // and returns false.
     static bool get_name(std::string& name) noexcept;
-
-private:
-#ifdef _WIN32
-    std::thread m_std_thread;
-#else
-    pthread_t m_id;
-#endif
-    bool m_joinable;
-    typedef void* (*entry_func_type)(void*);
-
-    void start(entry_func_type, void* arg);
-
-    template <class>
-    static void* entry_point(void*) noexcept;
-
-    REALM_NORETURN static void create_failed(int);
-    REALM_NORETURN static void join_failed(int);
 };
 
 
@@ -411,77 +356,6 @@ class CriticalSection {
 
 // Implementation:
 
-inline Thread::Thread()
-    : m_joinable(false)
-{
-}
-
-template <class F>
-inline Thread::Thread(F func)
-    : m_joinable(true)
-{
-    std::unique_ptr<F> func2(new F(func));       // Throws
-    start(&Thread::entry_point<F>, func2.get()); // Throws
-    func2.release();
-}
-
-inline Thread::Thread(Thread&& thread) noexcept
-{
-#ifndef _WIN32
-    m_id = thread.m_id;
-    m_joinable = thread.m_joinable;
-    thread.m_joinable = false;
-#endif
-}
-
-template <class F>
-inline void Thread::start(F func)
-{
-    if (m_joinable)
-        std::terminate();
-    std::unique_ptr<F> func2(new F(func));       // Throws
-    start(&Thread::entry_point<F>, func2.get()); // Throws
-    func2.release();
-    m_joinable = true;
-}
-
-inline Thread::~Thread() noexcept
-{
-    if (m_joinable)
-        REALM_TERMINATE("Destruction of joinable thread");
-}
-
-inline bool Thread::joinable() noexcept
-{
-    return m_joinable;
-}
-
-inline void Thread::start(entry_func_type entry_func, void* arg)
-{
-#ifdef _WIN32
-    m_std_thread = std::thread(entry_func, arg);
-#else
-    const pthread_attr_t* attr = nullptr; // Use default thread attributes
-    int r = pthread_create(&m_id, attr, entry_func, arg);
-    if (REALM_UNLIKELY(r != 0))
-        create_failed(r); // Throws
-#endif
-}
-
-template <class F>
-inline void* Thread::entry_point(void* cookie) noexcept
-{
-    std::unique_ptr<F> func(static_cast<F*>(cookie));
-    try {
-        (*func)();
-    }
-    catch (...) {
-        std::terminate();
-    }
-    return 0;
-}
-
-
 inline Mutex::Mutex()
 {
     init_as_regular();
@@ -806,7 +680,6 @@ void store_atomic(T& t_ref, T value, std::memory_order order)
 }
 
 
-} // namespace util
-} // namespace realm
+} // namespace realm::util
 
 #endif // REALM_UTIL_THREAD_HPP

src/realm/util/thread_exec_guard.hpp

@@ -1,13 +1,13 @@
 #ifndef REALM_UTIL_THREAD_EXEC_GUARD_HPP
 #define REALM_UTIL_THREAD_EXEC_GUARD_HPP
 
-#include <exception>
-#include <utility>
-#include <string>
-
-#include <realm/util/thread.hpp>
 #include <realm/util/signal_blocker.hpp>
+#include <realm/util/thread.hpp>
 
+#include <exception>
+#include <string>
+#include <thread>
+#include <utility>
 
 namespace realm {
 namespace util {
@@ -48,7 +48,7 @@ class ThreadExecGuard {
 private:
     struct State {
         R& runnable;
-        util::Thread thread;
+        std::thread thread;
         std::exception_ptr exception;
         State(R&) noexcept;
         ~State() noexcept;
@@ -114,7 +114,7 @@ class ThreadExecGuardWithParent {
     struct State {
         R& runnable;
         P& parent;
-        util::Thread thread;
+        std::thread thread;
         std::exception_ptr exception;
         State(R&, P&) noexcept;
         ~State() noexcept;
@@ -209,7 +209,7 @@ inline void ThreadExecGuard<R>::State::start(const std::string* thread_name)
             exception = std::current_exception();
         }
     };
-    thread.start(std::move(run)); // Throws
+    thread = std::thread(std::move(run)); // Throws
 }
 
 template <class R>
@@ -299,7 +299,7 @@ inline void ThreadExecGuardWithParent<R, P>::State::start(const std::string* thr
             parent.stop();
         }
     };
-    thread.start(std::move(run)); // Throws
+    thread = std::thread(std::move(run)); // Throws
 }
 
 template <class R, class P>