diff options
author | bors <bors@rust-lang.org> | 2018-01-28 13:24:47 +0000 |
---|---|---|
committer | bors <bors@rust-lang.org> | 2018-01-28 13:24:47 +0000 |
commit | 5e7fd65419384e5322fe18d3c6ea37e59860a9bc (patch) | |
tree | b408d493b9e6ff86c7b240e4b67557e056f4077f | |
parent | 0119b44270243db7479ea946bb0cdd5522c351b6 (diff) | |
parent | ed7e4e1e27d21d47b93f756e615b5cb750275c3f (diff) | |
download | rust-5e7fd65419384e5322fe18d3c6ea37e59860a9bc.tar.gz |
Auto merge of #47794 - etaoins:fix-ice-on-const-eval-of-union-field, r=eddyb
Fix ICE on const eval of union field
MIR's `Const::get_field()` attempts to retrieve the value for a given field in a constant. In the case of a union constant it was falling through to a generic `const_get_elt` based on the field index. As union fields don't have an index this caused an ICE in `llvm_field_index`.
Fix by simply returning the current value when accessing any field in a union. This works because all union fields start at byte offset 0.
The added test uses `const_fn` it ensure the field is extracted using MIR's const evaluation. The crash is reproducible without it, however.
Fixes #47788
r? @eddyb
-rw-r--r-- | src/librustc_trans/mir/constant.rs | 5 | ||||
-rw-r--r-- | src/test/run-pass/union/union-const-eval-field.rs | 45 |
2 files changed, 49 insertions, 1 deletions
diff --git a/src/librustc_trans/mir/constant.rs b/src/librustc_trans/mir/constant.rs index 71ce0aa3da9..f519e27dce9 100644 --- a/src/librustc_trans/mir/constant.rs +++ b/src/librustc_trans/mir/constant.rs @@ -140,7 +140,10 @@ impl<'a, 'tcx> Const<'tcx> { } } _ => { - const_get_elt(self.llval, layout.llvm_field_index(i)) + match layout.fields { + layout::FieldPlacement::Union(_) => self.llval, + _ => const_get_elt(self.llval, layout.llvm_field_index(i)), + } } } } diff --git a/src/test/run-pass/union/union-const-eval-field.rs b/src/test/run-pass/union/union-const-eval-field.rs new file mode 100644 index 00000000000..f83f49f298b --- /dev/null +++ b/src/test/run-pass/union/union-const-eval-field.rs @@ -0,0 +1,45 @@ +// 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. + +#![feature(const_fn)] + +type Field1 = i32; +type Field2 = f32; +type Field3 = i64; + +union DummyUnion { + field1: Field1, + field2: Field2, + field3: Field3, +} + +const FLOAT1_AS_I32: i32 = 1065353216; +const UNION: DummyUnion = DummyUnion { field1: FLOAT1_AS_I32 }; + +const fn read_field1() -> Field1 { + const FIELD1: Field1 = unsafe { UNION.field1 }; + FIELD1 +} + +const fn read_field2() -> Field2 { + const FIELD2: Field2 = unsafe { UNION.field2 }; + FIELD2 +} + +const fn read_field3() -> Field3 { + const FIELD3: Field3 = unsafe { UNION.field3 }; + FIELD3 +} + +fn main() { + assert_eq!(read_field1(), FLOAT1_AS_I32); + assert_eq!(read_field2(), 1.0); + assert_eq!(read_field3(), unsafe { UNION.field3 }); +} |