On Sat, Mar 17, 2018 at 01:07:32PM -0700, Kees Cook wrote: > On Sat, Mar 17, 2018 at 11:52 AM, Linus Torvalds > <torva...@linux-foundation.org> wrote: > > So the above is completely insane, bit there is actually a chance that > > using that completely crazy "x -> sizeof(char[x])" conversion actually > > helps, because it really does have a (very odd) evaluation-time > > change. sizeof() has to be evaluated as part of the constant > > expression evaluation, in ways that "__builtin_constant_p()" isn't > > specified to be done. > > > > But it is also definitely me grasping at straws. If that doesn't work > > for 4.4, there's nothing else I can possibly see. > > No luck! :( gcc 4.4 refuses to play along. And, hilariously, not only > does it not change the complaint about __builtin_choose_expr(), it > also thinks that's a VLA now. > > ./include/linux/mm.h: In function ‘get_mm_hiwater_rss’: > ./include/linux/mm.h:1567: warning: variable length array is used > ./include/linux/mm.h:1567: error: first argument to > ‘__builtin_choose_expr’ not a constant > > 6.8 is happy with it (of course). > > I do think the earlier version (without the > sizeof-hiding-builting_constant_p) provides a template for a > const_max() that both you and Rasmus would be happy with, though!
I thought we were dropping support for 4.4 (for other reasons). Isn't it 4.6 we should be looking at? -- Josh
