proc: bugfix: [OS X] desync of mach message queue in Continue

proc/proc.go

@@ -388,13 +388,8 @@ func (dbp *Process) Continue() error {
 			return dbp.exitGuard(err)
 		}
 		dbp.SwitchThread(thread.Id)
-		for _, th := range dbp.Threads {
-			if th.CurrentBreakpoint == nil {
-				err := th.SetCurrentBreakpoint()
-				if err != nil {
-					return err
-				}
-			}
+		if err := dbp.setExtraBreakpoints(); err != nil {
+			return err
 		}
 		loc, err := thread.Location()
 		if err != nil {

proc/proc_darwin.c

@@ -110,7 +110,7 @@ thread_count(task_t task) {
 }
 
 mach_port_t
-mach_port_wait(mach_port_t port_set) {
+mach_port_wait(mach_port_t port_set, int nonblocking) {
 	kern_return_t kret;
 	thread_act_t thread;
 	NDR_record_t *ndr;
@@ -120,9 +120,13 @@ mach_port_wait(mach_port_t port_set) {
 		mach_msg_header_t hdr;
 		char data[256];
 	} msg;
+	mach_msg_option_t opts = MACH_RCV_MSG|MACH_RCV_INTERRUPT;
+	if (nonblocking) {
+		opts |= MACH_RCV_TIMEOUT;
+	}
 
 	// Wait for mach msg.
-	kret = mach_msg(&msg.hdr, MACH_RCV_MSG|MACH_RCV_INTERRUPT,
+	kret = mach_msg(&msg.hdr, opts,
 			0, sizeof(msg.data), port_set, 0, MACH_PORT_NULL);
 	if (kret == MACH_RCV_INTERRUPTED) return kret;
 	if (kret != MACH_MSG_SUCCESS) return 0;
@@ -142,7 +146,7 @@ mach_port_wait(mach_port_t port_set) {
 			if (data[2] == EXC_SOFT_SIGNAL) {
 				if (data[3] != SIGTRAP) {
 					if (thread_resume(thread) != KERN_SUCCESS) return 0;
-					return mach_port_wait(port_set);
+					return mach_port_wait(port_set, nonblocking);
 				}
 			}
 			return thread;

proc/proc_darwin.go

@@ -111,7 +111,7 @@ func (dbp *Process) Kill() (err error) {
 		}
 	}
 	for {
-		port := C.mach_port_wait(dbp.os.portSet)
+		port := C.mach_port_wait(dbp.os.portSet, C.int(0))
 		if port == dbp.os.notificationPort {
 			break
 		}
@@ -268,7 +268,7 @@ func (dbp *Process) findExecutable(path string) (*macho.File, error) {
 
 func (dbp *Process) trapWait(pid int) (*Thread, error) {
 	for {
-		port := C.mach_port_wait(dbp.os.portSet)
+		port := C.mach_port_wait(dbp.os.portSet, C.int(0))
 
 		switch port {
 		case dbp.os.notificationPort:
@@ -318,6 +318,21 @@ func (dbp *Process) trapWait(pid int) (*Thread, error) {
 	}
 }
 
+func (dbp *Process) setExtraBreakpoints() error {
+	for {
+		port := C.mach_port_wait(dbp.os.portSet, C.int(1))
+		if port == 0 {
+			return nil
+		}
+		if th, ok := dbp.Threads[int(port)]; ok {
+			err := th.SetCurrentBreakpoint()
+			if err != nil {
+				return err
+			}
+		}
+	}
+}
+
 func (dbp *Process) loadProcessInformation(wg *sync.WaitGroup) {
 	wg.Done()
 }

proc/proc_darwin.h

@@ -36,7 +36,7 @@ int
 thread_count(task_t task);
 
 mach_port_t
-mach_port_wait(mach_port_t);
+mach_port_wait(mach_port_t, int);
 
 kern_return_t
 mach_send_reply(mach_msg_header_t);

proc/proc_linux.go

@@ -378,6 +378,18 @@ func (dbp *Process) wait(pid, options int) (int, *sys.WaitStatus, error) {
 	}
 }
 
+func (dbp *Process) setExtraBreakpoints() error {
+	for _, th := range dbp.Threads {
+		if th.CurrentBreakpoint == nil {
+			err := th.SetCurrentBreakpoint()
+			if err != nil {
+				return err
+			}
+		}
+	}
+	return nil
+}
+
 func (dbp *Process) exitGuard(err error) error {
 	if err != sys.ESRCH {
 		return err

proc/threads_darwin.go

@@ -31,7 +31,7 @@ func (t *Thread) singleStep() error {
 		return fmt.Errorf("could not single step")
 	}
 	for {
-		port := C.mach_port_wait(t.dbp.os.portSet)
+		port := C.mach_port_wait(t.dbp.os.portSet, C.int(0))
 		if port == C.mach_port_t(t.Id) {
 			break
 		}