On 17/11/2015 11:19, Peter Maydell wrote: > I think we should only take this patch if you can get a cast-iron > guarantee from both clang and gcc that they will never use this > UB to drive optimizations. As you say gcc already say this more or > less, but clang doesn't, and if they're warning about it that to > me suggests that they will feel freer to rely on the UB in future.
If and when this happens we will add "-fno-strict-overflow" for clang, just like we are using "-fno-strict-aliasing" already. > GCC is not our only supported compiler; UB is a real thing that > compilers in general take advantage of; we should be trying to > reduce our reliance on UB, not carving out extra areas where we > feel free to use it. We are already feeling free to use it. Paolo
