Arithmetic on `void'- and Function-Pointers
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In GNU C, addition and subtraction operations are supported on
pointers to `void' and on pointers to functions. This is done by
treating the size of a `void' or of a function as 1.
A consequence of this is that `sizeof' is also allowed on `void' and
on function types, and returns 1.
The option `-Wpointer-arith' requests a warning if these extensions
are used.