Sync core fixes from MESS done by OG (nw)

src/emu/dislot.c

@@ -10,6 +10,9 @@
 device_slot_interface::device_slot_interface(const machine_config &mconfig, device_t &device)
 	: device_interface(device)
 {
+	m_default_card = 0;
+	m_input_defaults = 0;
+	m_slot_interfaces = 0;
 }
 
 device_slot_interface::~device_slot_interface()

src/emu/mconfig.c

@@ -141,6 +141,33 @@ screen_device *machine_config::first_screen() const
 
 device_t *machine_config::device_add(device_t *owner, const char *tag, device_type type, UINT32 clock)
 {
+	const char *orig_tag = tag;
+
+	// if the device path is absolute, start from the root
+	if (tag[0] == ':')
+	{
+		tag++;
+		owner = m_root_device;
+	}
+
+	// go down the path until we're done with it
+	while (strchr(tag, ':'))
+	{
+		const char *next = strchr(tag, ':');
+		assert(next != tag);
+		astring part(tag, next-tag);
+		device_t *curdevice;
+		for (curdevice = owner->m_subdevice_list.first(); curdevice != NULL; curdevice = curdevice->next())
+			if (part == curdevice->m_basetag)
+				break;
+		if (!curdevice)
+			throw emu_fatalerror("Could not find %s when looking up path for device %s\n",
+								 part.cstr(), orig_tag);
+		owner = curdevice;
+		tag = next+1;
+	}
+	assert(tag[0]);
+
 	// if there's an owner, let the owner do the work
 	if (owner != NULL)
 		return owner->add_subdevice(type, tag, clock);

src/emu/mconfig.h

@@ -51,8 +51,8 @@
 //  CONSTANTS
 //**************************************************************************
 
-// by convention, tags should all lowercase and between 2-15 characters
+// by convention, tags should all lowercase and between 1-15 characters
-#define MIN_TAG_LENGTH			2
+#define MIN_TAG_LENGTH			1
 #define MAX_TAG_LENGTH			15
 
 

src/emu/validity.c

@@ -1139,7 +1139,7 @@ void validity_checker::validate_slots()
 	{
 		// iterate over interfaces
 		const slot_interface *intf = slot->get_slot_interfaces();
-		for (int j = 0; intf[j].name != NULL; j++)
+		for (int j = 0; intf && intf[j].name != NULL; j++)
 		{
 			// instantiate the device
 			device_t *dev = (*intf[j].devtype)(*m_current_config, "dummy", &m_current_config->root_device(), 0);