70fe20a698
This reverts commit a0ec902e23 "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.
30 lines
731 B
Rust
30 lines
731 B
Rust
// Copyright 2014 The Rust Project Developers. See the COPYRIGHT
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// file at the top-level directory of this distribution and at
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// http://rust-lang.org/COPYRIGHT.
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//
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// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
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// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
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// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
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// option. This file may not be copied, modified, or distributed
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// except according to those terms.
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pub struct Foo {
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f1: int,
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_f2: int,
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}
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#[inline(never)]
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pub fn foo(f: &mut Foo) -> Foo {
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let ret = *f;
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f.f1 = 0;
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ret
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}
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pub fn main() {
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let mut f = Foo {
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f1: 8,
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_f2: 9,
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};
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f = foo(&mut f);
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assert_eq!(f.f1, 8);
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}
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