Am 01.02.2017 um 12:47 schrieb Jeff King:

I'm not altogether convinced that SWAP() is an improvement in
readability. I really like that it's shorter than the code it replaces,
but there is a danger with introducing opaque constructs. It's one more
thing for somebody familiar with C but new to the project to learn or
get wrong.

I'm biased, of course, but SIMPLE_SWAP and SWAP exchange the values of 
two variables -- how could someone get that wrong?  Would it help to 
name the macro SWAP_VALUES?  Or XCHG? ;)

IMHO the main maintenance gain from René's patch is that you don't have
to specify the type, which means you can never have a memory-overflow
bug due to incorrect types. If we lose that, then I don't see all that
much value in the whole thing.

Size checks could be added to SIMPLE_SWAP as well.

The main benefit of a swap macro is reduced repetition IMHO: Users 
specify the variables to swap once instead of twice in a special order, 
and with SWAP they don't need to declare their type again.  Squeezing 
out redundancy makes the code easier to read and modify.

René