It is invalid to use sizeof() with a function
type expression (C99 '6.5.3.4 para. 1) and hence this code invokes
undefined behavior. gcc gives a warning if you compile with
-pedantic,
but otherwise it apparently just returns 1;
But this is actually a BUG in gcc - look at 5.1.1.3. The restriction
that sizeof may not have an argument that is function type is a
constraint, and therefore a breach requires a diagnostic.
There is no bug, as GCC prints a diagnostic just fine.
That's what -pedantic is for.
Segher
