If I return a Vec buffer and a pointer to its internal data, is the pointer valid?-CodePudding

I'm writing some C FFI bindings, and I came up with a situation which I'm unsure whether it works or not. In its simplest form, it would be:

unsafe fn foo() -> (*const u8, Vec<u8>) {
    let buf = vec![0, 1, 2];
    (buf.as_ptr(), buf)
}

Now using it:

fn main() {
    let (ptr, _buf) = foo();

    // pass ptr to C function...
}

In the example above, is ptr valid, since _buf lives until the end of the scope?

CodePudding user response：

The question is whether moving the Vec invalidates the pointer into it. And the answer is, it's not decided yet.

This is UCG issue #326.

So it is best to avoid code like that until it is decided. But for what it's worth, as a lot of code relies on that to work, I don't believe it will be decided to be invalid.