languages/rust
languages/rust
1
0
Fork 0
mirror of https://github.com/rust-lang/rust synced 2024-10-17 14:03:42 +00:00
Code Issues Packages Projects Releases Wiki Activity

Rollup merge of #106779 - RReverser:patch-2, r=Mark-Simulacrum

Browse source 
Avoid __cxa_thread_atexit_impl on Emscripten

 - Fixes https://github.com/rust-lang/rust/issues/91628.
 - Fixes https://github.com/emscripten-core/emscripten/issues/15722.

See discussion in both issues.

The TL;DR is that weak linkage causes LLVM to produce broken Wasm, presumably due to pointer mismatch. The code is casting a void pointer to a function pointer with specific signature, but Wasm is very strict about function pointer compatibility, so the resulting code is invalid.

Ideally LLVM should catch this earlier in the process rather than emit invalid Wasm, but it currently doesn't and this is an easy and valid fix, given that Emcripten doesn't have `__cxa_thread_atexit_impl` these days anyway.

Unfortunately, I can't add a regression test as even after looking into this issue for a long time, I couldn't reproduce it with any minimal Rust example, only with extracted LLVM IR or on a large project involving Rust + C++.
This commit is contained in:
Matthias Krüger 2023-01-26 07:53:22 +01:00 committed by GitHub
parent b2448f9f9c a41c5f9c38
commit cc92bdb9c9
No known key found for this signature in database
GPG key ID: 4AEE18F83AFDEB23
1 changed files with 3 additions and 8 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

11
library/std/src/sys/unix/thread_local_dtor.rs
View file

@ -11,13 +11,7 @@
// Note, however, that we run on lots older linuxes, as well as cross
// compiling from a newer linux to an older linux, so we also have a
// fallback implementation to use as well.
#[cfg(any(
target_os = "linux",
target_os = "fuchsia",
target_os = "redox",
target_os = "emscripten"
))]
#[cfg_attr(target_family = "wasm", allow(unused))] // might remain unused depending on target details (e.g. wasm32-unknown-emscripten)
#[cfg(any(target_os = "linux", target_os = "fuchsia", target_os = "redox"))]
pub unsafe fn register_dtor(t: *mut u8, dtor: unsafe extern "C" fn(*mut u8)) {
use crate::mem;
use crate::sys_common::thread_local_dtor::register_dtor_fallback;
@ -89,7 +83,8 @@ pub unsafe fn register_dtor(t: *mut u8, dtor: unsafe extern "C" fn(*mut u8)) {
}
}
#[cfg(any(target_os = "vxworks", target_os = "horizon"))]
#[cfg(any(target_os = "vxworks", target_os = "horizon", target_os = "emscripten"))]
#[cfg_attr(target_family = "wasm", allow(unused))] // might remain unused depending on target details (e.g. wasm32-unknown-emscripten)
pub unsafe fn register_dtor(t: *mut u8, dtor: unsafe extern "C" fn(*mut u8)) {
use crate::sys_common::thread_local_dtor::register_dtor_fallback;
register_dtor_fallback(t, dtor);