[PUSB] Fix static initialization order fiasco

For details see:
https://isocpp.org/wiki/faq/ctors#static-init-order-on-first-use

Author: facchinm

hardware/arduino/avr/cores/arduino/PluggableUSB.cpp

@@ -25,8 +25,6 @@
 
 extern uint8_t _initEndpoints[];
 
-PluggableUSB_ PluggableUSB;
-
 int PluggableUSB_::getInterface(uint8_t* interfaceNum)
 {
 	int sent = 0;
@@ -90,6 +88,12 @@ bool PluggableUSB_::plug(PUSBListNode *node)
 	// restart USB layer???
 }
 
+PluggableUSB_& PluggableUSB()
+{
+	static PluggableUSB_ obj;
+	return obj;
+}
+
 PluggableUSB_::PluggableUSB_() : lastIf(CDC_ACM_INTERFACE + CDC_INTERFACE_COUNT),
                                  lastEp(CDC_FIRST_ENDPOINT + CDC_ENPOINT_COUNT),
                                  rootNode(NULL)

hardware/arduino/avr/cores/arduino/PluggableUSB.h

@@ -66,7 +66,10 @@ class PluggableUSB_ {
   PUSBListNode* rootNode;
 };
 
-extern PluggableUSB_ PluggableUSB;
+// Replacement for global singleton.
+// This function prevents static-initialization-order-fiasco
+// https://isocpp.org/wiki/faq/ctors#static-init-order-on-first-use
+PluggableUSB_& PluggableUSB();
 
 #endif
 

hardware/arduino/avr/cores/arduino/USBCore.cpp

@@ -362,7 +362,7 @@ bool ClassInterfaceRequest(USBSetup& setup)
 		return CDC_Setup(setup);
 
 #ifdef PLUGGABLE_USB_ENABLED
-	return PluggableUSB.setup(setup, i);
+	return PluggableUSB().setup(setup, i);
 #endif
 	return false;
 }
@@ -440,7 +440,7 @@ static u8 SendInterfaces()
 	CDC_GetInterface(&interfaces);
 
 #ifdef PLUGGABLE_USB_ENABLED
-	PluggableUSB.getInterface(&interfaces);
+	PluggableUSB().getInterface(&interfaces);
 #endif
 
 	return interfaces;
@@ -476,7 +476,7 @@ bool SendDescriptor(USBSetup& setup)
 
 	InitControl(setup.wLength);
 #ifdef PLUGGABLE_USB_ENABLED
-	ret = PluggableUSB.getDescriptor(t);
+	ret = PluggableUSB().getDescriptor(t);
 	if (ret != 0) {
 		return (ret > 0 ? true : false);
 	}