Hi René,

On Mon, 30 Jan 2017, 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.

Thank you for clarifying.

> > 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".

Okay, now we know what the tool says.

I would like to take a step back and state that it does not make much
sense to support SWAP(a++, b), as it is confusing at best.

Ciao,
Dscho