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Use ABI alignment, not "preferred" alignment, to unify monomorphizations.

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See the comment in the added test case for details.
This commit is contained in:
Jed Davis 2013-06-03 22:34:51 -07:00
parent 133d451715
commit 0c9510ac38
2 changed files with 37 additions and 2 deletions
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8
src/librustc/middle/trans/monomorphize.rs
View File

@ -30,7 +30,7 @@ use middle::trans::type_use;
use middle::ty; use middle::ty;
use middle::ty::{FnSig}; use middle::ty::{FnSig};
use middle::typeck; use middle::typeck;
use util::ppaux::Repr; use util::ppaux::{Repr,ty_to_str};
use core::vec; use core::vec;
use syntax::ast; use syntax::ast;
@ -379,10 +379,14 @@ pub fn make_mono_id(ccx: @CrateContext,
{ {
let llty = type_of::type_of(ccx, subst); let llty = type_of::type_of(ccx, subst);
let size = machine::llbitsize_of_real(ccx, llty); let size = machine::llbitsize_of_real(ccx, llty);
let align = machine::llalign_of_pref(ccx, llty); let align = machine::llalign_of_min(ccx, llty);
let mode = datum::appropriate_mode(subst); let mode = datum::appropriate_mode(subst);
let data_class = mono_data_classify(subst); let data_class = mono_data_classify(subst);
debug!("make_mono_id: type %s -> size %u align %u mode %? class %?",
ty_to_str(ccx.tcx, subst),
size, align, mode, data_class);
// Special value for nil to prevent problems // Special value for nil to prevent problems
// with undef return pointers. // with undef return pointers.
if size <= 8u && ty::type_is_nil(subst) { if size <= 8u && ty::type_is_nil(subst) {

31
src/test/run-pass/monomorphize-abi-alignment.rs Normal file
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@ -0,0 +1,31 @@
// Copyright 2013 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.
/*!
* On x86_64-linux-gnu and possibly other platforms, structs get 8-byte "preferred" alignment,
* but their "ABI" alignment (i.e., what actually matters for data layout) is the largest alignment
* of any field. (Also, u64 has 8-byte ABI alignment; this is not always true).
*
* On such platforms, if monomorphize uses the "preferred" alignment, then it will unify
* `A` and `B`, even though `S<A>` and `S<B>` have the field `t` at different offsets,
* and apply the wrong instance of the method `unwrap`.
*/
struct S<T> { i:u8, t:T }
impl<T> S<T> { fn unwrap(self) -> T { self.t } }
struct A((u32, u32));
struct B(u64);
pub fn main() {
static Ca: S<A> = S { i: 0, t: A((13, 104)) };
static Cb: S<B> = S { i: 0, t: B(31337) };
assert_eq!(*(Ca.unwrap()), (13, 104));
assert_eq!(*(Cb.unwrap()), 31337);
}