bjoernager/rust
bjoernager/rust
1
Fork 0
Code Activity

Add discussion that concurrent access to the environment is unsafe

Browse source 
The bug report #27970 has existed for 8 years, the actual bug dates back
to Rust pre-1.0. I documented it since it's in the interest of the user
to be aware of it. The note can be removed once #27970 is fixed.
This commit is contained in:
Tobias Bucher 2023-10-18 14:59:53 +02:00
parent e8b8c78d84
commit 8057586d3d
1 changed files with 28 additions and 10 deletions
Download patch file Download diff file Expand all files Collapse all files

38
library/std/src/env.rs
View file

@ -313,17 +313,26 @@ impl Error for VarError {
/// Sets the environment variable `key` to the value `value` for the currently running
/// process.
///
/// Note that while concurrent access to environment variables is safe in Rust,
/// some platforms only expose inherently unsafe non-threadsafe APIs for
/// inspecting the environment. As a result, extra care needs to be taken when
/// auditing calls to unsafe external FFI functions to ensure that any external
/// environment accesses are properly synchronized with accesses in Rust.
/// Note that while concurrent access to environment variables ought to be safe
/// in Rust, some platforms only expose inherently unsafe non-threadsafe APIs
/// for inspecting the environment. As a result, using `set_var` or
/// `remove_var` in a multi-threaded Rust program can lead to undefined
/// behavior, for example in combination with DNS lookups from
/// [`std::net::ToSocketAddrs`]. This is a bug
/// ([rust#27970](https://github.com/rust-lang/rust/issues/27970)) and will be
/// fixed in a future version of Rust. Additionally, extra care needs to be
/// taken when auditing calls to unsafe external FFI functions to ensure that
/// any external environment accesses are properly synchronized with accesses
/// in Rust. Since Rust does not expose its environment lock directly, this
/// means that all accesses to the environment must go through Rust's [`var`].
///
/// Discussion of this unsafety on Unix may be found in:
///
/// - [Austin Group Bugzilla](https://austingroupbugs.net/view.php?id=188)
/// - [GNU C library Bugzilla](https://sourceware.org/bugzilla/show_bug.cgi?id=15607#c2)
///
/// [`std::net::ToSocketAddrs`]: crate::net::ToSocketAddrs
///
/// # Panics
///
/// This function may panic if `key` is empty, contains an ASCII equals sign `'='`
@ -351,17 +360,26 @@ fn _set_var(key: &OsStr, value: &OsStr) {
/// Removes an environment variable from the environment of the currently running process.
///
/// Note that while concurrent access to environment variables is safe in Rust,
/// some platforms only expose inherently unsafe non-threadsafe APIs for
/// inspecting the environment. As a result extra care needs to be taken when
/// auditing calls to unsafe external FFI functions to ensure that any external
/// environment accesses are properly synchronized with accesses in Rust.
/// Note that while concurrent access to environment variables ought to be safe
/// in Rust, some platforms only expose inherently unsafe non-threadsafe APIs
/// for inspecting the environment. As a result, using `set_var` or
/// `remove_var` in a multi-threaded Rust program can lead to undefined
/// behavior, for example in combination with DNS lookups from
/// [`std::net::ToSocketAddrs`]. This is a bug
/// ([rust#27970](https://github.com/rust-lang/rust/issues/27970)) and will be
/// fixed in a future version of Rust. Additionally, extra care needs to be
/// taken when auditing calls to unsafe external FFI functions to ensure that
/// any external environment accesses are properly synchronized with accesses
/// in Rust. Since Rust does not expose its environment lock directly, this
/// means that all accesses to the environment must go through Rust's [`var`].
///
/// Discussion of this unsafety on Unix may be found in:
///
/// - [Austin Group Bugzilla](https://austingroupbugs.net/view.php?id=188)
/// - [GNU C library Bugzilla](https://sourceware.org/bugzilla/show_bug.cgi?id=15607#c2)
///
/// [`std::net::ToSocketAddrs`]: crate::net::ToSocketAddrs
///
/// # Panics
///
/// This function may panic if `key` is empty, contains an ASCII equals sign