On 01/30, René Scharfe wrote:
> Am 30.01.2017 um 22:03 schrieb Johannes Schindelin:
> >It is curious, though, that an
> >expression like "sizeof(a++)" would not be rejected.
>
> Clang normally warns about something like this ("warning: expression
> with side effects has no effect in an unevaluated context
> [-Wunevaluated-expression]"), but not if the code is part of a
> macro. I don't know if that's intended, but it sure is helpful in
> the case of SWAP.
>
> >Further, what would SWAP(a++, b) do? Swap a and b, and *then* increment a?
>
> That might be a valid expectation, but GCC says "error: lvalue
> required as unary '&' operand" and clang puts it "error: cannot take
> the address of an rvalue of type".
>
> René
Perhaps we could disallow a side-effect operator in the macro. By
disallow I mean place a comment at the definition to the macro and
hopefully catch something like that in code-review. We have the same
issue with the `ALLOC_GROW()` macro.
--
Brandon Williams