Stimulus[Buffer|Frame]: initial impl, unoptimized for mem use

include/user/stagingBuffer.h

@@ -31,6 +31,9 @@ public:
 	class IOEngineConstraints
 	{
 	public:
+		// Default constructor creates uninitialized constraints
+		IOEngineConstraints() = default;
+
 		IOEngineConstraints(
 			size_t slotStartAlignmentByteVal_,
 			size_t slotPadToNBytes_,
@@ -65,6 +68,12 @@ public:
 	};
 
 public:
+	/**	EXPLANATION:
+	 * Default constructor creates uninitialized buffer.
+	 * Must be properly initialized using placement new with the parameterized constructor.
+	 */
+	StagingBuffer() = default;
+
 	/**	EXPLANATION:
 	 * We use the input and output engine constraints to determine the total
 	 * amount of memory required internally to assemble a single frame with
@@ -144,6 +153,8 @@ private:
 	struct MmapDeleter
 	{
 		size_t size;
+		// Default constructor for use with default-constructed StagingBuffer
+		MmapDeleter() : size(0) {}
 		MmapDeleter(size_t s) : size(s) {}
 		
 		void operator()(uint8_t* ptr) const