extensive orb_advert_t fixes

The calls to orb_advertise were being mishandled throughout the code.
There were ::close() calls on memory pointers, there were checks
against < 0 when it is a pointer to a object and values larger than
0x7ffffffff are valid. Some places orb_advert_t variables were
being initialized as 0 other places as -1.

The orb_advert_t type was changed to uintptr_t so the pointer value
would not be wrapped as a negative number. This was causing a failure
on ARM.

Tests for < 0 were changed to == 0 since a null pointer is the valid
representation for error, or uninitialized.

Signed-off-by: Mark Charlebois <charlebm@gmail.com>

src/modules/uavcan/sensors/gnss.cpp

@@ -48,7 +48,7 @@ const char *const UavcanGnssBridge::NAME = "gnss";
 UavcanGnssBridge::UavcanGnssBridge(uavcan::INode &node) :
 _node(node),
 _sub_fix(node),
-_report_pub(-1)
+_report_pub(0)
 {
 }
 

src/modules/uavcan/sensors/sensor_bridge.cpp

@@ -119,7 +119,7 @@ void UavcanCDevSensorBridgeBase::publish(const int node_id, const void *report)
 		channel->class_instance = class_instance;
 
 		channel->orb_advert = orb_advertise_multi(_orb_topic, report, &channel->orb_instance, ORB_PRIO_HIGH);
-		if (channel->orb_advert < 0) {
+		if (channel->orb_advert == 0) {
 			log("ADVERTISE FAILED");
 			(void)unregister_class_devname(_class_devname, class_instance);
 			*channel = Channel();