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

H. Peter Anvin
2007-01-09T17:08:56Z

Robert P. J. Day wrote:
> 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.
>

Well, you can apparently not use it as a part of a constant expression
(which makes sense; do-while is illegal there too.) That would be the
only case in which an expression is permitted outside a function at all.

-hpa