ExceptionPorts test: accept a port of MACH_PORT_NULL as “no handler.”

util/mach/exception_ports.cc

 // Copyright 2014 The Crashpad Authors. All rights reserved.
 //
 // Licensed under the Apache License, Version 2.0 (the "License");
 // you may not use this file except in compliance with the License.
 // You may obtain a copy of the License at
 //
 //     http://www.apache.org/licenses/LICENSE-2.0
 //
 // Unless required by applicable law or agreed to in writing, software
 // distributed under the License is distributed on an "AS IS" BASIS,
@@ skipping 81 matching lines @@
 
   kern_return_t kr = get_exception_ports_(
       target_port_, mask, masks, &handler_count, ports, behaviors, flavors);
   if (kr != KERN_SUCCESS) {
     MACH_LOG(ERROR, kr) << TargetTypeName() << "_get_exception_ports";
     return false;
   }
 
   handlers->clear();
   for (mach_msg_type_number_t index = 0; index < handler_count; ++index) {
-    ExceptionHandler handler;
-    handler.mask = masks[index];
-    handler.port = ports[index];
-    handler.behavior = behaviors[index];
-    handler.flavor = flavors[index];
-    handlers->push_back(handler);
+    if (ports[index] != MACH_PORT_NULL) {
+      ExceptionHandler handler;
+      handler.mask = masks[index];
+      handler.port = ports[index];
+      handler.behavior = behaviors[index];
+      handler.flavor = flavors[index];
+      handlers->push_back(handler);
+    }
   }
 
   return true;
 }
 
 bool ExceptionPorts::SetExceptionPort(exception_mask_t mask,
                                       exception_handler_t port,
                                       exception_behavior_t behavior,
                                       thread_state_flavor_t flavor) const {
   kern_return_t kr =
       set_exception_ports_(target_port_, mask, port, behavior, flavor);
   if (kr != KERN_SUCCESS) {
     MACH_LOG(ERROR, kr) << TargetTypeName() << "_set_exception_ports";
     return false;
   }
 
   return true;
 }
 
 const char* ExceptionPorts::TargetTypeName() const {
   return target_name_;
 }
 
 }  // namespace crashpad