Fix fallthrough warnings on gcc 7

src/gdb_main.c

@@ -155,7 +155,7 @@ int gdb_main_loop(struct target_controller *tc, bool in_syscall)
 			}
 		case 's':	/* 's [addr]': Single step [start at addr] */
 			single_step = true;
-			// Fall through to resume target
+			/* fall through */
 		case 'c':	/* 'c [addr]': Continue [at addr] */
 			if(!cur_target) {
 				gdb_putpacketz("X1D");
@@ -165,7 +165,7 @@ int gdb_main_loop(struct target_controller *tc, bool in_syscall)
 			target_halt_resume(cur_target, single_step);
 			SET_RUN_STATE(1);
 			single_step = false;
-			// Fall through to wait for target halt
+			/* fall through */
 		case '?': {	/* '?': Request reason for target halt */
 			/* This packet isn't documented as being mandatory,
 			 * but GDB doesn't work without it. */
@@ -482,4 +482,3 @@ void gdb_main(void)
 {
 	gdb_main_loop(&gdb_controller, false);
 }
-

src/platforms/common/cdcacm.c

@@ -445,6 +445,7 @@ static int cdcacm_control_request(usbd_device *dev,
 		switch(req->wIndex) {
 		case 2:
 			usbuart_set_line_coding((struct usb_cdc_line_coding*)*buf);
+			return 1;
 		case 0:
 			return 1; /* Ignore on GDB Port */
 		default:
@@ -462,6 +463,7 @@ static int cdcacm_control_request(usbd_device *dev,
 
 			return 1;
 		}
+		return 0;
 	case DFU_DETACH:
 		if(req->wIndex == DFU_IF_NO) {
 			*complete = dfu_detach_complete;
@@ -561,4 +563,3 @@ void USB_ISR(void)
 {
 	usbd_poll(usbdev);
 }
-