6 ms·

Was it the one with the elided null check?

• aka-rider 15d ago
  I don't remember the details, roughly it was unexpected invocation of move semantic, causing use after free in a loop. My all-time favourite example is (again, my memory, I may be a bit wrong): for (int i = 0; i < (size_t)limit; ++i) { } at some point limit could potentially become greater than INT_MAX, the compiler decided that i<limit could never be true because that would cause signed int overflow which is UB, so it "optimized" the loop into while(true) signed unsigned mismatch makes me shiver
  • dgrunwald 15d ago
    The compiler cannot optimize that into `while(true)` because the original code does not encounter undefined behavior when `limit` is small enough to fit into `int`. What it can do: infer that `limit <= INT_MAX` and use that to optimize the code following after the loop (and in some cases, even the code before the loop).
    • aka-rider 15d ago
      This isn't complete example. I don't remember the details unfortunately. But somehow compiler has decided that i <= limit is always true.