src/doc/trpl/intrinsics.md

   1 % Intrinsics
   2
   3 > **Note**: intrinsics will forever have an unstable interface, it is
   4 > recommended to use the stable interfaces of libcore rather than intrinsics
   5 > directly.
   6
   7 These are imported as if they were FFI functions, with the special
   8 `rust-intrinsic` ABI. For example, if one was in a freestanding
   9 context, but wished to be able to `transmute` between types, and
  10 perform efficient pointer arithmetic, one would import those functions
  11 via a declaration like
  12
  13 ```rust
  14 # #![feature(intrinsics)]
  15 # fn main() {}
  16
  17 extern "rust-intrinsic" {
  18     fn transmute<T, U>(x: T) -> U;
  19
  20     fn offset<T>(dst: *const T, offset: isize) -> *const T;
  21 }
  22 ```
  23
  24 As with any other FFI functions, these are always `unsafe` to call.
  25