NRF5: Enable critical section (#879)

drivers/CircularBuffer/CircularBuffer.h

@@ -1,4 +1,4 @@
-/*
+/*
   CircularBuffer - An Arduino circular buffering library for arbitrary types.
 
   Created by Ivo Pullens, Emmission, 2014-2016 -- www.emmission.nl
@@ -88,9 +88,11 @@ public:
 	 */
 	inline uint8_t available(void) const
 	{
+		uint8_t ret_value;
 		MY_CRITICAL_SECTION {
-			return m_fill;
+			ret_value = m_fill;
 		}
+		return ret_value;
 	}
 
 	/**

hal/architecture/MyHwNRF5.h

@@ -130,9 +130,7 @@ typedef struct {
 } nrf_ecb_t;
 
 #ifndef DOXYGEN
-#define MY_CRITICAL_SECTION
-// temp. commented, to fix "CircularBuffer.h:94:2: warning: control reaches end of non-void function" error
-#define __MY_CRITICAL_SECTION                                                    \
+#define MY_CRITICAL_SECTION                                                    \
 	for (uint32_t __savePriMask                                                  \
 	        __attribute__((__cleanup__(__priMaskRestore))) = __get_PRIMASK(),       \
 	        __ToDo = __disableIntsRetVal();                                         \