Hi Peff, On Tue, 31 Jan 2017, Jeff King wrote: > On Tue, Jan 31, 2017 at 10:03:01PM +0100, René Scharfe wrote: > > > > 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. > > > > SWAP(a++, ...) is caught by the compiler, SWAP(*a++, ...) works fine. > > Technically that should be enough. :) A comment wouldn't hurt, of > > course. > > One funny thing is that your macro takes address-of itself, behind the > scenes. I wonder if it would be more natural for it to take > pointers-to-objects, making it look more like a real function (i.e., > SWAP(&a, &b) instead of SWAP(a, b)". And then these funny corner cases > become quite obvious in the caller, because the caller is the one who > has to type "&". But forcing SWAP(&a, &b) would make it even more cumbersome to use, and it would also make it harder to optimize, say, by using registers instead of addressable memory (think swapping two 32-bit integers: there is *no* need to write them into memory just to swap them). And I think I should repeat my point that this discussion veers towards making simple swaps *more* complicated, rather than less complicated. Bad direction. Ciao, Dscho