rust/tests/ui/out-pointer-aliasing.rs

//@ run-pass

#[derive(Copy, Clone)]
pub struct Foo {
    f1: isize,
    _f2: isize,
}

#[inline(never)]
pub fn foo(f: &mut Foo) -> Foo {
    let ret = *f;
    f.f1 = 0;
    ret
}

pub fn main() {
    let mut f = Foo {
        f1: 8,
        _f2: 9,
    };
    f = foo(&mut f);
    assert_eq!(f.f1, 8);
}
tests: Add missing run-pass annotations 2019-07-26 21:54:25 +00:00			`//@ run-pass`

Fallout in tests 2015-03-30 13:38:27 +00:00			`#[derive(Copy, Clone)]`
Fix codegen breaking aliasing rules for functions with sret results This reverts commit a0ec902e239b2219edf1a18b036dd32c18d3be42 "Avoid unnecessary temporary on assignments". Leaving out the temporary for the functions return value can lead to a situation that conflicts with rust's aliasing rules. Given this: ````rust fn func(f: &mut Foo) -> Foo { /* ... / } fn bar() { let mut foo = Foo { / ... */ }; foo = func(&mut foo); } ```` We effectively get two mutable references to the same variable `foo` at the same time. One for the parameter `f`, and one for the hidden out-pointer. So we can't just `trans_into` the destination directly, but must use `trans` to get a new temporary slot from which the result can be copied. 2014-10-22 19:23:26 +00:00			`pub struct Foo {`
Mass rename uint/int to usize/isize Now that support has been removed, all lingering use cases are renamed. 2015-03-26 00:06:52 +00:00			`f1: isize,`
			`_f2: isize,`
Fix codegen breaking aliasing rules for functions with sret results This reverts commit a0ec902e239b2219edf1a18b036dd32c18d3be42 "Avoid unnecessary temporary on assignments". Leaving out the temporary for the functions return value can lead to a situation that conflicts with rust's aliasing rules. Given this: ````rust fn func(f: &mut Foo) -> Foo { /* ... / } fn bar() { let mut foo = Foo { / ... */ }; foo = func(&mut foo); } ```` We effectively get two mutable references to the same variable `foo` at the same time. One for the parameter `f`, and one for the hidden out-pointer. So we can't just `trans_into` the destination directly, but must use `trans` to get a new temporary slot from which the result can be copied. 2014-10-22 19:23:26 +00:00			`}`

			`#[inline(never)]`
			`pub fn foo(f: &mut Foo) -> Foo {`
			`let ret = *f;`
			`f.f1 = 0;`
			`ret`
			`}`

			`pub fn main() {`
			`let mut f = Foo {`
			`f1: 8,`
			`_f2: 9,`
			`};`
			`f = foo(&mut f);`
			`assert_eq!(f.f1, 8);`
			`}`