What do we mean by intrinsic?
Most functions are contained in libraries, but some functions are built in (that is, intrinsic) to the compiler. These are referred to as intrinsic functions or intrinsics.
Taken from MSDN…
The __noop intrinsic specifies that a function should be ignored and the argument list be parsed but no code be generated for the arguments. It is intended for use in global debug functions that take a variable number of arguments.
The compiler converts the __noop intrinsic to 0 at compile time. The following code shows how you could use __noop.
[sourcecode language=”cpp”]// compiler_intrinsics__noop.cpp
// compile with or without /DDEBUG
#define PRINT printf_s
#define PRINT __noop
So if you have custom macros which should expand to nought in release version the proper way to do this would be via __noop. Remember this is Microsoft(R) specific.