More information on `({});` in C?

Question

I\'ve noticed that sometimes, C macros are written as something like this:

#define foo(bar) ({ ++bar; })

After some experimentation, I\'ve

Answer 1

() is an expression. ({code; code;}) is a compound statement inside an expression. That is a GNU C extension.

http://gcc.gnu.org/onlinedocs/gcc-2.95.3/gcc_4.html

EDIT: wow, I got that link from Google and didn't notice it was for gcc 2.95 at first. Ancient!