On: Can a local variable's memory be accessed outside ...

[mikeash]

It is often instructive and useful to look at the behavior of real implementations, not just the idealized behavior given by the standard.

[bentcorner → mikeash]

Indeed - sometimes you run into something and think "that shouldn't have worked", and it's useful to understand why.

[IsTom → mikeash]

When compiled with -O3 using g++ it returns 0 8. Compiler will use undefined behavior to optimize.

[mikeash → IsTom]

There's a fun example with clang where you can have two pointers where:

    x == y

But:

    *x != *y

It involves invoking undefined behavior by using a pointer after it's been freed and arranging for a new pointer at the exact same location. Clang cached the contents of the old pointer and uses it in the comparison.