From 408eeae59d35cbcaab2cfb345d24373954e74fc5 Mon Sep 17 00:00:00 2001 From: Obei Sideg Date: Sat, 17 Feb 2024 22:01:56 +0300 Subject: Improve wording of static_mut_ref Rename `static_mut_ref` lint to `static_mut_refs`. --- .../rustc_error_codes/src/error_codes/E0796.md | 26 +++++++++++++--------- 1 file changed, 15 insertions(+), 11 deletions(-) (limited to 'compiler/rustc_error_codes') diff --git a/compiler/rustc_error_codes/src/error_codes/E0796.md b/compiler/rustc_error_codes/src/error_codes/E0796.md index cea18f8db85..7ac429e5215 100644 --- a/compiler/rustc_error_codes/src/error_codes/E0796.md +++ b/compiler/rustc_error_codes/src/error_codes/E0796.md @@ -1,22 +1,26 @@ -Reference of mutable static. +You have created a reference to a mutable static. Erroneous code example: ```compile_fail,edition2024,E0796 static mut X: i32 = 23; -static mut Y: i32 = 24; -unsafe { - let y = &X; - let ref x = X; - let (x, y) = (&X, &Y); - foo(&X); +fn work() { + let _val = unsafe { X }; } -fn foo<'a>(_x: &'a i32) {} +let x_ref = unsafe { &mut X }; +work(); +// The next line has Undefined Behavior! +// `x_ref` is a mutable reference and allows no aliases, +// but `work` has been reading the reference between +// the moment `x_ref` was created and when it was used. +// This violates the uniqueness of `x_ref`. +*x_ref = 42; ``` -Mutable statics can be written to by multiple threads: aliasing violations or -data races will cause undefined behavior. +A reference to a mutable static has lifetime `'static`. This is very dangerous +as it is easy to accidentally overlap the lifetime of that reference with +other, conflicting accesses to the same static. -Reference of mutable static is a hard error from 2024 edition. +References to mutable statics are a hard error in the 2024 edition. -- cgit 1.4.1-3-g733a5