[threads] Return boolean instead of pointer from Thread_internal (#6661)

configure.ac

@@ -40,7 +40,7 @@ MONO_VERSION_BUILD=`echo $VERSION | cut -d . -f 3`
 # This can be reset to 0 when Mono's version number is bumped
 # since it's part of the corlib version (the prefix '1' in the full
 # version number is to ensure the number isn't treated as octal in C)
-MONO_CORLIB_COUNTER=3
+MONO_CORLIB_COUNTER=4
 MONO_CORLIB_VERSION=`printf "1%02d%02d%02d%03d" $MONO_VERSION_MAJOR $MONO_VERSION_MINOR 0 $MONO_CORLIB_COUNTER`
 
 AC_DEFINE_UNQUOTED(MONO_CORLIB_VERSION,$MONO_CORLIB_VERSION,[Version of the corlib-runtime interface])

mcs/class/corlib/System.Threading/Thread.cs

@@ -311,7 +311,7 @@ namespace System.Threading {
 
 		// Returns the system thread handle
 		[MethodImplAttribute(MethodImplOptions.InternalCall)]
-		private extern IntPtr Thread_internal (MulticastDelegate start);
+		private extern bool Thread_internal (MulticastDelegate start);
 
 		private Thread (InternalThread it) {
 			internal_thread = it;
@@ -484,7 +484,7 @@ namespace System.Threading {
 #endif
 
 			// Thread_internal creates and starts the new thread, 
-			if (Thread_internal(m_Delegate) == IntPtr.Zero)
+			if (!Thread_internal(m_Delegate))
 				throw new SystemException ("Thread creation failed.");
 
 			m_ThreadStartArg = null;

mono/metadata/threads-types.h

@@ -82,7 +82,8 @@ mono_thread_create_internal (MonoDomain *domain, gpointer func, gpointer arg, Mo
 void mono_threads_install_cleanup (MonoThreadCleanupFunc func);
 
 void ves_icall_System_Threading_Thread_ConstructInternalThread (MonoThread *this_obj);
-gpointer ves_icall_System_Threading_Thread_Thread_internal(MonoThread *this_obj, MonoObject *start);
+MonoBoolean
+ves_icall_System_Threading_Thread_Thread_internal (MonoThread *this_obj, MonoObject *start);
 void ves_icall_System_Threading_InternalThread_Thread_free_internal(MonoInternalThread *this_obj);
 void ves_icall_System_Threading_Thread_Sleep_internal(gint32 ms);
 gboolean ves_icall_System_Threading_Thread_Join_internal(MonoThread *this_obj, int ms);

mono/metadata/threads.c

@@ -1421,7 +1421,7 @@ ves_icall_System_Threading_Thread_GetCurrentThread (MonoError *error)
 	return MONO_HANDLE_NEW (MonoThreadObject, mono_thread_current ());
 }
 
-HANDLE
+MonoBoolean
 ves_icall_System_Threading_Thread_Thread_internal (MonoThread *this_obj,
 												   MonoObject *start)
 {
@@ -1440,19 +1440,19 @@ ves_icall_System_Threading_Thread_Thread_internal (MonoThread *this_obj,
 	if ((internal->state & ThreadState_Unstarted) == 0) {
 		UNLOCK_THREAD (internal);
 		mono_set_pending_exception (mono_get_exception_thread_state ("Thread has already been started."));
-		return NULL;
+		return FALSE;
 	}
 
 	if ((internal->state & ThreadState_Aborted) != 0) {
 		UNLOCK_THREAD (internal);
-		return this_obj;
+		return TRUE;
 	}
 
 	res = create_thread (this_obj, internal, start, NULL, NULL, MONO_THREAD_CREATE_FLAGS_NONE, error);
 	if (!res) {
 		mono_error_cleanup (error);
 		UNLOCK_THREAD (internal);
-		return NULL;
+		return FALSE;
 	}
 
 	internal->state &= ~ThreadState_Unstarted;
@@ -1460,7 +1460,7 @@ ves_icall_System_Threading_Thread_Thread_internal (MonoThread *this_obj,
 	THREAD_DEBUG (g_message ("%s: Started thread ID %"G_GSIZE_FORMAT" (handle %p)", __func__, tid, thread));
 
 	UNLOCK_THREAD (internal);
-	return internal->handle;
+	return TRUE;
 }
 
 /*