4 files changed, 64 insertions, 21 deletions
diff --git a/cores/arduino/CDC.cpp b/cores/arduino/CDC.cpp
index f19b44c..0a743e1 100644
--- a/cores/arduino/CDC.cpp
+++ b/cores/arduino/CDC.cpp
@@ -34,6 +34,8 @@ typedef struct
 static volatile LineInfo _usbLineInfo = { 57600, 0x00, 0x00, 0x00, 0x00 };
 static volatile int32_t breakValue = -1;
 
+bool _updatedLUFAbootloader = false;
+
 #define WEAK __attribute__ ((weak))
 
 extern const CDCDescriptor _cdcInterface PROGMEM;
@@ -99,24 +101,32 @@ bool CDC_Setup(USBSetup& setup)
 			// with a relatively long period so it can finish housekeeping tasks
 			// like servicing endpoints before the sketch ends
 
-#ifndef MAGIC_KEY
-#define MAGIC_KEY 0x7777
-#endif
-#ifndef MAGIC_KEY_POS
-#define MAGIC_KEY_POS 0x0800
+			uint16_t magic_key_pos = MAGIC_KEY_POS;
+
+// If we don't use the new RAMEND directly, check manually if we have a newer bootloader.
+// This is used to keep compatible with the old leonardo bootloaders.
+// You are still able to set the magic key position manually to RAMEND-1 to save a few bytes for this check.
+#if MAGIC_KEY_POS != (RAMEND-1)
+			// For future boards save the key in the inproblematic RAMEND
+			// Which is reserved for the main() return value (which will never return)
+			if (_updatedLUFAbootloader) {
+				// horray, we got a new bootloader!
+				magic_key_pos = (RAMEND-1);
+			}
 #endif
 
 			// We check DTR state to determine if host port is open (bit 0 of lineState).
 			if (1200 == _usbLineInfo.dwDTERate && (_usbLineInfo.lineState & 0x01) == 0)
 			{
 #if MAGIC_KEY_POS != (RAMEND-1)
-				*(uint16_t *)(RAMEND-1) = *(uint16_t *)MAGIC_KEY_POS;
-				*(uint16_t *)MAGIC_KEY_POS = MAGIC_KEY;
-#else
-				// for future boards save the key in the inproblematic RAMEND
-				// which is reserved for the main() return value (which will never return)
-				*(uint16_t *)MAGIC_KEY_POS = MAGIC_KEY;
+				// Backup ram value if its not a newer bootloader.
+				// This should avoid memory corruption at least a bit, not fully
+				if (magic_key_pos != (RAMEND-1)) {
+					*(uint16_t *)(RAMEND-1) = *(uint16_t *)magic_key_pos;
+				}
 #endif
+				// Store boot key
+				*(uint16_t *)magic_key_pos = MAGIC_KEY;
 				wdt_enable(WDTO_120MS);
 			}
 			else
@@ -129,10 +139,15 @@ bool CDC_Setup(USBSetup& setup)
 				wdt_disable();
 				wdt_reset();
 #if MAGIC_KEY_POS != (RAMEND-1)
-				*(uint16_t *)MAGIC_KEY_POS = *(uint16_t *)(RAMEND-1);
-#else
-				*(uint16_t *)MAGIC_KEY_POS = 0x0000;
+				// Restore backed up (old bootloader) magic key data
+				if (magic_key_pos != (RAMEND-1)) {
+					*(uint16_t *)magic_key_pos = *(uint16_t *)(RAMEND-1);
+				} else
 #endif
+				{
+				// Clean up RAMEND key
+					*(uint16_t *)magic_key_pos = 0x0000;
+				}
 			}
 		}
 		return true;
diff --git a/cores/arduino/USBCore.cpp b/cores/arduino/USBCore.cpp
index 62b90ed..3c7da86 100644
--- a/cores/arduino/USBCore.cpp
+++ b/cores/arduino/USBCore.cpp
@@ -35,6 +35,7 @@ extern const u8 STRING_PRODUCT[] PROGMEM;
 extern const u8 STRING_MANUFACTURER[] PROGMEM;
 extern const DeviceDescriptor USB_DeviceDescriptor PROGMEM;
 extern const DeviceDescriptor USB_DeviceDescriptorB PROGMEM;
+extern bool _updatedLUFAbootloader;
 
 const u16 STRING_LANGUAGE[2] = {
 	(3<<8) | (2+2),
@@ -806,6 +807,12 @@ void USBDevice_::attach()
 	UDIEN = (1<<EORSTE) | (1<<SOFE) | (1<<SUSPE);	// Enable interrupts for EOR (End of Reset), SOF (start of frame) and SUSPEND
 	
 	TX_RX_LED_INIT;
+
+#if MAGIC_KEY_POS != (RAMEND-1)
+	if (pgm_read_word(FLASHEND - 1) == NEW_LUFA_SIGNATURE) {
+		_updatedLUFAbootloader = true;
+	}
+#endif
 }
 
 void USBDevice_::detach()
diff --git a/cores/arduino/USBCore.h b/cores/arduino/USBCore.h
index 4e08d71..66f3b5b 100644
--- a/cores/arduino/USBCore.h
+++ b/cores/arduino/USBCore.h
@@ -277,5 +277,22 @@ typedef struct
 #define D_CDCCS(_subtype,_d0,_d1)	{ 5, 0x24, _subtype, _d0, _d1 }
 #define D_CDCCS4(_subtype,_d0)		{ 4, 0x24, _subtype, _d0 }
 
+// Bootloader related fields
+// Old Caterina bootloader places the MAGIC key into unsafe RAM locations (it can be rewritten
+// by the running sketch before to actual reboot).
+// Newer bootloaders, recognizable by the LUFA "signature" at the end of the flash, can handle both
+// the usafe and the safe location. Check once (in USBCore.cpp) if the bootloader in new, then set the global
+// _updatedLUFAbootloader variable to true/false and place the magic key consequently
+#ifndef MAGIC_KEY
+#define MAGIC_KEY 0x7777
+#endif
+
+#ifndef MAGIC_KEY_POS
+#define MAGIC_KEY_POS 0x0800
+#endif
+
+#ifndef NEW_LUFA_SIGNATURE
+#define NEW_LUFA_SIGNATURE 0xDCFB
+#endif
 
 #endif
diff --git a/cores/arduino/WString.h b/cores/arduino/WString.h
index b047980..de5632c 100644
--- a/cores/arduino/WString.h
+++ b/cores/arduino/WString.h
@@ -81,7 +81,7 @@ public:
 	inline unsigned int length(void) const {return len;}
 
 	// creates a copy of the assigned value.  if the value is null or
-	// invalid, or if the memory allocation fails, the string will be 
+	// invalid, or if the memory allocation fails, the string will be
 	// marked as invalid ("if (s)" will be false).
 	String & operator = (const String &rhs);
 	String & operator = (const char *cstr);
@@ -92,10 +92,10 @@ public:
 	#endif
 
 	// concatenate (works w/ built-in types)
-	
+
 	// returns true on success, false on failure (in which case, the string
-	// is left unchanged).  if the argument is null or invalid, the 
-	// concatenation is considered unsucessful.  
+	// is left unchanged).  if the argument is null or invalid, the
+	// concatenation is considered unsucessful.
 	unsigned char concat(const String &str);
 	unsigned char concat(const char *cstr);
 	unsigned char concat(char c);
@@ -107,7 +107,7 @@ public:
 	unsigned char concat(float num);
 	unsigned char concat(double num);
 	unsigned char concat(const __FlashStringHelper * str);
-	
+
 	// if there's not enough memory for the concatenated value, the string
 	// will be left unchanged (but this isn't signalled in any way)
 	String & operator += (const String &rhs)	{concat(rhs); return (*this);}
@@ -159,8 +159,12 @@ public:
 	char& operator [] (unsigned int index);
 	void getBytes(unsigned char *buf, unsigned int bufsize, unsigned int index=0) const;
 	void toCharArray(char *buf, unsigned int bufsize, unsigned int index=0) const
-		{getBytes((unsigned char *)buf, bufsize, index);}
-	const char * c_str() const { return buffer; }
+		{ getBytes((unsigned char *)buf, bufsize, index); }
+	const char* c_str() const { return buffer; }
+	char* begin() { return buffer; }
+	char* end() { return buffer + length(); }
+	const char* begin() const { return c_str(); }
+	const char* end() const { return c_str() + length(); }
 
 	// search
 	int indexOf( char ch ) const;