To give credit where credit is due, this hack was inspired by an equally insane (but different) use of the ?: operator to choose the right return type for type-generic macros in tgmath.h.
https://sourceware.org/git/?p=glibc.git;a=blob;f=math/tgmath.h;h=a709a5 9d0fa1168ef03349561169fc5bd27d65aa;hb=d8742dd82f6a00601155c69bad3012e90 5591e1f (recommendation: don't look) Martin Am Montag, den 26.03.2018, 14:52 -1000 schrieb Linus Torvalds: > On Mon, Mar 26, 2018 at 12:15 PM, Kees Cook <keesc...@chromium.org> > wrote: > > > > This patch updates the min()/max() macros to evaluate to a constant > > expression when called on constant expression arguments. > > Ack. > > I'm of two minds whether that "__is_constant()" macro should be > explained or not. > > A small voice in my head says "that wants a comment". > > But a bigger voice disagrees. > > It is a work of art, and maybe the best documentation is just the > name. It does what it says it does. > > Art shouldn't be explained. It should be appreciated. > > Nobody sane really should care about how it works, and if somebody > cares it is "left as an exercise to the reader". > > Linus
