Skip to content
New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Fix an ICE when attempting to transmute an uninhabited type #50803

Merged
merged 2 commits into from
May 20, 2018
Merged
Show file tree
Hide file tree
Changes from all commits
Commits
File filter

Filter by extension

Filter by extension

Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
17 changes: 14 additions & 3 deletions src/librustc_codegen_llvm/mir/block.rs
Original file line number Diff line number Diff line change
Expand Up @@ -428,9 +428,20 @@ impl<'a, 'tcx> FunctionCx<'a, 'tcx> {
let intrinsic = intrinsic.as_ref().map(|s| &s[..]);

if intrinsic == Some("transmute") {
let &(ref dest, target) = destination.as_ref().unwrap();
self.codegen_transmute(&bx, &args[0], dest);
funclet_br(self, bx, target);
if let Some(destination_ref) = destination.as_ref() {
let &(ref dest, target) = destination_ref;
self.codegen_transmute(&bx, &args[0], dest);
funclet_br(self, bx, target);
} else {
// If we are trying to transmute to an uninhabited type,
// it is likely there is no allotted destination. In fact,
// transmuting to an uninhabited type is UB, which means
// we can do what we like. Here, we declare that transmuting
// into an uninhabited type is impossible, so anything following
// it must be unreachable.
assert_eq!(bx.cx.layout_of(sig.output()).abi, layout::Abi::Uninhabited);
bx.unreachable();
}
return;
}

Expand Down
33 changes: 33 additions & 0 deletions src/test/compile-fail/never_transmute_never.rs
Original file line number Diff line number Diff line change
@@ -0,0 +1,33 @@
// Copyright 2018 The Rust Project Developers. See the COPYRIGHT
// file at the top-level directory of this distribution and at
// http://rust-lang.org/COPYRIGHT.
//
// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
// option. This file may not be copied, modified, or distributed
// except according to those terms.

// compile-pass

#![crate_type="lib"]

#![feature(never_type)]
#![allow(dead_code)]
#![allow(unreachable_code)]
#![allow(unused_variables)]

struct Foo;

pub fn f(x: !) -> ! {
x
}

pub fn ub() {
// This is completely undefined behaviour,
// but we still want to make sure it compiles.
let x: ! = unsafe {
std::mem::transmute::<Foo, !>(Foo)
};
f(x)
}