Typecasting or function Pointer?

While CPallini is of course correct, the reason for your confusion may have been the somewhat involved pointer modification in the expression (*(volatile unsigned int *)(address))

In this expression:
- unsigned int is the base type used for a (C-style) type-cast
- volatile is a type modifier (such as const), telling the compiler that the unsigned int value accessed here may change at any time
- (volatile unsigned int*) is a type-cast to 'pointer to a volatile value of type unsigned int'
- (address) is the argument to the type-cast; the brackets may be necessary, if an expression is used as an address rather than a variable or literal

A function pointer type definition looks a bit similar due to the surrounding '()', the obligatory '*', and the function argument list. I've tried to figure out how this should look like if it were to be the assignment of a function pointer, i.e. if the type cast were meant to change the type of address to a function pointer, which gets assigned a new value:

(unsigned int (cdecl)())(address) = value

[edit]Checked with the compiler and fixed the type cast syntax; but the compiler doesn't accept it anyway since it won't let me assign a value to a function pointer [/edit]

Note the additional empty set of () after (address). It gives away the fact we're dealing with a function pointer rather than an ordinary one. Also, I left out volatile, because that's an invalid qualifier for return types (or, in other words, the volatile in your expression is an indication this is not a function pointer)

Hello

volatile means that operation will be performed with variable directly without using accumulator register, that mostly used in cases of multithreaded variables accessing.
For that porpose better usage of Interlocked functions.
Actually in your case: (assigment) can be used InterlockedExchange or InterlockedExchangePointer functions they are more safety then simple volatile assignment. If you not performs cross threading variables usage in that macro - then simple assignmet will be fine.

Regards,
Maxim.