src/test/run-pass/nullable-pointer-ffi-compat.rs

   1 // Copyright 2014 The Rust Project Developers. See the COPYRIGHT
   2 // file at the top-level directory of this distribution and at
   3 // http://rust-lang.org/COPYRIGHT.
   4 //
   5 // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
   6 // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
   7 // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
   8 // option. This file may not be copied, modified, or distributed
   9 // except according to those terms.
  10
  11 // #11303, #11040:
  12 // This would previously crash on i686 Linux due to abi differences
  13 // between returning an Option<T> and T, where T is a non nullable
  14 // pointer.
  15 // If we have an enum with two variants such that one is zero sized
  16 // and the other contains a nonnullable pointer, we don't use a
  17 // separate discriminant. Instead we use that pointer field to differentiate
  18 // between the 2 cases.
  19 // Also, if the variant with the nonnullable pointer has no other fields
  20 // then we simply express the enum as just a pointer and not wrap it
  21 // in a struct.
  22
  23
  24 use std::mem;
  25
  26 #[inline(never)]
  27 extern "C" fn foo(x: &isize) -> Option<&isize> { Some(x) }
  28
  29 static FOO: isize = 0xDEADBEE;
  30
  31 pub fn main() {
  32     unsafe {
  33         let f: extern "C" fn(&isize) -> &isize =
  34             mem::transmute(foo as extern "C" fn(&isize) -> Option<&isize>);
  35         assert_eq!(*f(&FOO), FOO);
  36     }
  37 }