question about interpreter

Sat Apr 1 00:00:00 GMT 2000

In the interpreter code I see defines like this:
 #define LOADL(I) ({ jint __idx = (I); \
	(sp++)->ia[0] = locals[__idx].ia[0]; \
	(sp++)->ia[0] = locals[__idx+1].ia[0]; \
 })
As far as I can tell all uses of this macro (and those like it) are
statements and not expressions. Is there a reason we're using ({...})
and not simply {...}? This causes many warnings ("value computed not
used") from gcc.
Tom