macros: "do-while" versus "({ })" and a compile-time error

Robert P. J. Day
2007-01-08T18:57:47Z

just to stir the pot a bit regarding the discussion of the two
different ways to define macros, i've just noticed that the "({ })"
notation is not universally acceptable. i've seen examples where
using that notation causes gcc to produce:

error: braced-group within expression allowed only inside a function

i wasn't aware that there were limits on this notation. can someone
clarify this? under what circumstances *can't* you use that notation?
thanks.

rday