raw_parts

Peeling back safe abstractions on heap data.

#![allow(unused)]
fn main() {
impl<T> Vec<T> {
    // Note how this is an unsafe function
    unsafe fn from_raw_parts(ptr: *mut T, length: usize, capacity: usize) -> Vec<T>;

    fn into_raw_parts(self) -> (*mut T, usize, usize);
}
}

  • raw_parts denotes methods that construct items from or decompose items into underlying pointer data and its relevant layout information (capacity, etc.).

  • These kinds of methods can be marked as unsafe if constructing new values as trust is placed on the user to avoid conditions that might lead to undefined behavior.

    Such a case might be passing a pointer of sizeof T * 10 to Vec::from_raw_parts but also passing 20 as the capacity argument, which would lead to writing or accessing values 10 through 19 in the vector being undefined behavior.