Auto merge of rust-lang#116123 - joboet:rewrite_native_tls, r=<try>

Rewrite native thread-local storage

(part of rust-lang#110897)

The current native thread-local storage implementation has become quite messy, uses indescriptive names and unnecessarily adds code to the macro expansion. This PR tries to fix that by using a new implementation that also allows more layout optimizations and potentially increases performance by eliminating unnecessary TLS accesses.

This does not change the recursive initialization behaviour I described in [this comment](rust-lang#110897 (comment)), so it should be a library-only change. Changing that behaviour should be quite easy now, however.

r? `@m-ou-se`
`@rustbot` label +T-libs

library/std/src/sys/thread_local/mod.rs

@@ -15,7 +15,7 @@ cfg_if::cfg_if! {
         #[doc(hidden)]
         mod fast_local;
         #[doc(hidden)]
-        pub use fast_local::{Key, thread_local_inner};
+        pub use fast_local::{Storage, take_or_call, thread_local_inner};
     } else {
         #[doc(hidden)]
         mod os_local;
@@ -24,6 +24,9 @@ cfg_if::cfg_if! {
     }
 }
 
+// Not used by the fast-local TLS anymore.
+// FIXME(#110897): remove this.
+#[allow(unused)]
 mod lazy {
     use crate::cell::UnsafeCell;
     use crate::hint;

library/std/src/thread/mod.rs

@@ -205,7 +205,7 @@ cfg_if::cfg_if! {
         #[doc(hidden)]
         #[unstable(feature = "thread_local_internals", issue = "none")]
         pub mod local_impl {
-            pub use crate::sys::thread_local::{thread_local_inner, Key, abort_on_dtor_unwind};
+            pub use crate::sys::thread_local::*;
         }
     }
 }

src/tools/tidy/src/issues.txt

@@ -4009,8 +4009,6 @@
 "ui/test-attrs/issue-53675-a-test-called-panic.rs",
 "ui/threads-sendsync/issue-24313.rs",
 "ui/threads-sendsync/issue-29488.rs",
-"ui/threads-sendsync/issue-43733-2.rs",
-"ui/threads-sendsync/issue-43733.rs",
 "ui/threads-sendsync/issue-4446.rs",
 "ui/threads-sendsync/issue-4448.rs",
 "ui/threads-sendsync/issue-8827.rs",

tests/ui/suggestions/missing-lifetime-specifier.rs

@@ -1,6 +1,11 @@
-// different number of duplicated diagnostics on different targets
-//@ only-x86_64
-//@ only-linux
+// The specific errors produced depend the thread-local implementation.
+// Run only on platforms with "fast" TLS.
+//@ ignore-windows FIXME(#84933)
+//@ ignore-wasm globals are used instead of thread locals
+//@ ignore-emscripten globals are used instead of thread locals
+//@ ignore-android does not use #[thread_local]
+//@ ignore-nto does not use #[thread_local]
+// Different number of duplicated diagnostics on different targets
 //@ compile-flags: -Zdeduplicate-diagnostics=yes
 
 #![allow(bare_trait_objects)]
@@ -20,31 +25,31 @@ pub union Qux<'t, 'k, I> {
 trait Tar<'t, 'k, I> {}
 
 thread_local! {
-    //~^ ERROR lifetime may not live long enough
-    //~| ERROR lifetime may not live long enough
+    //~^ ERROR borrowed data escapes outside of function
+    //~| ERROR borrowed data escapes outside of function
     static a: RefCell<HashMap<i32, Vec<Vec<Foo>>>> = RefCell::new(HashMap::new());
       //~^ ERROR missing lifetime specifiers
       //~| ERROR missing lifetime specifiers
 }
 thread_local! {
-    //~^ ERROR lifetime may not live long enough
-    //~| ERROR lifetime may not live long enough
-    //~| ERROR lifetime may not live long enough
+    //~^ ERROR borrowed data escapes outside of function
+    //~| ERROR borrowed data escapes outside of function
+    //~| ERROR borrowed data escapes outside of function
     static b: RefCell<HashMap<i32, Vec<Vec<&Bar>>>> = RefCell::new(HashMap::new());
       //~^ ERROR missing lifetime specifiers
       //~| ERROR missing lifetime specifiers
 }
 thread_local! {
-    //~^ ERROR lifetime may not live long enough
-    //~| ERROR lifetime may not live long enough
+    //~^ ERROR borrowed data escapes outside of function
+    //~| ERROR borrowed data escapes outside of function
     static c: RefCell<HashMap<i32, Vec<Vec<Qux<i32>>>>> = RefCell::new(HashMap::new());
     //~^ ERROR missing lifetime specifiers
     //~| ERROR missing lifetime specifiers
 }
 thread_local! {
-    //~^ ERROR lifetime may not live long enough
-    //~| ERROR lifetime may not live long enough
-    //~| ERROR lifetime may not live long enough
+    //~^ ERROR borrowed data escapes outside of function
+    //~| ERROR borrowed data escapes outside of function
+    //~| ERROR borrowed data escapes outside of function
     static d: RefCell<HashMap<i32, Vec<Vec<&Tar<i32>>>>> = RefCell::new(HashMap::new());
     //~^ ERROR missing lifetime specifiers
     //~| ERROR missing lifetime specifiers