alt Hacker NewsThe special part is the "signal handler trick" that is easy to use for 32-bit pointers. You reserve 4GB of memory - all that 32 bits can address - and mark everything above used memory as trapping. Then you can just do normal reads and writes, and the CPU hardware checks out of bounds.
With 64-bit pointers, you can't really reserve all the possible space a pointer might refer to. So you end up doing manual bounds checks.
Hi Alon! It's been a while.
Can't bounds checks be avoided in the vast majority of cases?
See my reply to nagisa above (https://news.ycombinator.com/item?id=45283102). It feels like by using trailing unmapped barrier/guard regions, one should be able to elide almost all bounds checks that occur in the program with a bit of compiler cleverness, and convert them into trap handlers instead.