1 files changed, 77 insertions, 0 deletions
diff --git a/ctr-std/src/sys/horizon/fast_thread_local.rs b/ctr-std/src/sys/horizon/fast_thread_local.rs
new file mode 100644
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+++ b/ctr-std/src/sys/horizon/fast_thread_local.rs
@@ -0,0 +1,77 @@
+// Copyright 2014-2015 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.
+
+#![cfg(target_thread_local)]
+#![unstable(feature = "thread_local_internals", issue = "0")]
+
+// Since what appears to be glibc 2.18 this symbol has been shipped which
+// GCC and clang both use to invoke destructors in thread_local globals, so
+// let's do the same!
+//
+// 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.
+//
+// Due to rust-lang/rust#18804, make sure this is not generic!
+#[cfg(target_os = "linux")]
+pub unsafe fn register_dtor(t: *mut u8, dtor: unsafe extern fn(*mut u8)) {
+    use libc;
+    use mem;
+    use sys_common::thread_local::register_dtor_fallback;
+
+    extern {
+        #[linkage = "extern_weak"]
+        static __dso_handle: *mut u8;
+        #[linkage = "extern_weak"]
+        static __cxa_thread_atexit_impl: *const libc::c_void;
+    }
+    if !__cxa_thread_atexit_impl.is_null() {
+        type F = unsafe extern fn(dtor: unsafe extern fn(*mut u8),
+                                  arg: *mut u8,
+                                  dso_handle: *mut u8) -> libc::c_int;
+        mem::transmute::<*const libc::c_void, F>(__cxa_thread_atexit_impl)
+            (dtor, t, &__dso_handle as *const _ as *mut _);
+        return
+    }
+    register_dtor_fallback(t, dtor);
+}
+
+// macOS's analog of the above linux function is this _tlv_atexit function.
+// The disassembly of thread_local globals in C++ (at least produced by
+// clang) will have this show up in the output.
+#[cfg(target_os = "macos")]
+pub unsafe fn register_dtor(t: *mut u8, dtor: unsafe extern fn(*mut u8)) {
+    extern {
+        fn _tlv_atexit(dtor: unsafe extern fn(*mut u8),
+                       arg: *mut u8);
+    }
+    _tlv_atexit(dtor, t);
+}
+
+// Just use the thread_local fallback implementation, at least until there's
+// a more direct implementation.
+#[cfg(target_os = "fuchsia")]
+pub use sys_common::thread_local::register_dtor_fallback as register_dtor;
+
+pub fn requires_move_before_drop() -> bool {
+    // The macOS implementation of TLS apparently had an odd aspect to it
+    // where the pointer we have may be overwritten while this destructor
+    // is running. Specifically if a TLS destructor re-accesses TLS it may
+    // trigger a re-initialization of all TLS variables, paving over at
+    // least some destroyed ones with initial values.
+    //
+    // This means that if we drop a TLS value in place on macOS that we could
+    // revert the value to its original state halfway through the
+    // destructor, which would be bad!
+    //
+    // Hence, we use `ptr::read` on macOS (to move to a "safe" location)
+    // instead of drop_in_place.
+    cfg!(target_os = "macos")
+}