I2CSlave: do not use vla

Author: pennam

libraries/Wire/Wire.cpp

@@ -159,11 +159,12 @@ void arduino::MbedI2C::receiveThd() {
 				}
 				if (usedTxBuffer != 0) {
 					core_util_critical_section_enter();
-					uint8_t tempTxBuffer[usedTxBuffer];
-					memcpy(tempTxBuffer, txBuffer, sizeof(tempTxBuffer));
+					uint8_t tempTxBuffer[256];
+					uint8_t usedTempTxBuffer = usedTxBuffer;
+					memcpy(tempTxBuffer, txBuffer, usedTempTxBuffer);
 					usedTxBuffer = 0;
 					core_util_critical_section_exit();
-					slave->write((const char *) tempTxBuffer, sizeof(tempTxBuffer));
+					slave->write((const char *) tempTxBuffer, usedTempTxBuffer);
 				}
 				//slave->stop();
 				break;