RFC: C++ Buffer Hardening

[FabioFracassi]

@lemire

Given that the functionality is supposed to be built as clang warnings, you can always do a

#pragma clang diagnostic push
#pragma clang diagnostic ignored "-Wunsafe-buffer-usage"
// pointer arithmetic
#pragma clang diagnostic pop

Please be mindful that these pragmas are not portable, they are relatively ugly and difficult to maintain. To get it to work in portable code, you probably need twice as much complexity.

and to add insult to injury making them less ugly usually (is there even another way?) means macros, which do not mesh well with modules.

also this warning currently fires at the one place where (afaict) there is no getting around it. int main(int argc, char const** argv)