How do I make a C++ macro behave like a function?

I had seen this code before, and never understood why it was written the way it was. Now I do! Here's the background:

A macro acting like a function should allow this to work as expected:

123	if (cond) FUNC(x, y); do_stuff();

As well as:

if (cond)
	FUNC(x, y);
else
	FUNC(y, x);
do_stuff();

But not:

123	do_stuff(); FUNC(x, y) // note no semicolon do_stuff();

If you write a naive function as a set of commands, you violate all of the expectations.

123	#define FUNC(x, y) \ print x; \ print y; \

Of course, you can introduce braces for scope:

#define FUNC(x, y)		\
{				\
	print x;		\
	print y;		\
}

But now the third is still violated - no semicolon yet it still works. Here's an interesting bit of code that I finally understand, that solves all three problems:

#define FUNC(x, y)		\
do {				\
	print x;		\
	print y;		\
} while (0)

Reference: StackOverflow

Ches Koblents