VS2013 x64 compiler bug Note how the access to m_size (loaded into edx) is reordered to be after the detachBuffer() call:

bug.asm

; 12   : {

$LN6:
	sub	rsp, 40					; 00000028H

; 13   : 	AllocatingBuffer outBuf;

	lea	rcx, QWORD PTR outBuf$[rsp]
	call	??0AllocatingBuffer@@QEAA@XZ		; AllocatingBuffer::AllocatingBuffer

; 14   : 	int size = outBuf.size();
; 15   : 	create(outBuf.detachBuffer(), size);

	lea	rcx, QWORD PTR outBuf$[rsp]
	call	?detachBuffer@AllocatingBuffer@@QEAAPEADXZ ; AllocatingBuffer::detachBuffer
	mov	edx, DWORD PTR outBuf$[rsp]
	mov	rcx, rax
	call	?create@@YAPEAVSharedBuffer@@PEADH@Z	; create

; 16   : }

bug.cpp

// Compile using VS2013 x64 with "cl /c /FAs /O2 bug.cpp"
//
// Note how the access to m_size is reordered to be after the detachBuffer() call

struct AllocatingBuffer 
{
	AllocatingBuffer();
	char* detachBuffer();
	int size() { return m_size; }
	int		m_size;
};

class SharedBuffer* create(char* memory, int size);

void acquireInfoFromBuffer()
{
	AllocatingBuffer outBuf;
	int size = outBuf.size();
	create(outBuf.detachBuffer(), size);
}