Check #[thread_local] statics correctly in the compiler.

Author: eddyb

src/librustc/middle/mem_categorization.rs

@@ -643,7 +643,13 @@ impl<'a, 'gcx, 'tcx> MemCategorizationContext<'a, 'gcx, 'tcx> {
                 Ok(self.cat_rvalue_node(id, span, expr_ty))
           }
 
-          Def::Static(_, mutbl) => {
+          Def::Static(def_id, mutbl) => {
+            // `#[thread_local]` statics may not outlive the current function.
+            for attr in &self.tcx.get_attrs(def_id)[..] {
+                if attr.check_name("thread_local") {
+                    return Ok(self.cat_rvalue_node(id, span, expr_ty));
+                }
+            }
               Ok(Rc::new(cmt_ {
                   id:id,
                   span:span,

src/librustc_mir/diagnostics.rs

@@ -442,4 +442,5 @@ static A : &'static u32 = &S.a; // ok!
 
 register_diagnostics! {
     E0526, // shuffle indices are not constant
+    E0625, // thread-local statics cannot be accessed at compile-time
 }

src/librustc_mir/transform/qualify_consts.rs

@@ -484,8 +484,20 @@ impl<'a, 'tcx> Visitor<'tcx> for Qualifier<'a, 'tcx, 'tcx> {
                     }
                 }
             },
-            Lvalue::Static(_) => {
+            Lvalue::Static(ref global) => {
                 self.add(Qualif::STATIC);
+
+                if self.mode != Mode::Fn {
+                    for attr in &self.tcx.get_attrs(global.def_id)[..] {
+                        if attr.check_name("thread_local") {
+                            span_err!(self.tcx.sess, self.span, E0625,
+                                      "thread-local statics cannot be \
+                                       accessed at compile-time");
+                            return;
+                        }
+                    }
+                }
+
                 if self.mode == Mode::Const || self.mode == Mode::ConstFn {
                     span_err!(self.tcx.sess, self.span, E0013,
                               "{}s cannot refer to statics, use \
@@ -998,6 +1010,12 @@ impl MirPass for QualifyAndPromoteConstants {
 
         // Statics must be Sync.
         if mode == Mode::Static {
+            // `#[thread_local]` statics don't have to be `Sync`.
+            for attr in &tcx.get_attrs(def_id)[..] {
+                if attr.check_name("thread_local") {
+                    return;
+                }
+            }
             let ty = mir.return_ty;
             tcx.infer_ctxt().enter(|infcx| {
                 let param_env = ty::ParamEnv::empty(Reveal::UserFacing);

src/libstd/lib.rs

@@ -243,6 +243,7 @@
 #![feature(allocator_api)]
 #![feature(alloc_system)]
 #![feature(allocator_internals)]
+#![feature(allow_internal_unsafe)]
 #![feature(allow_internal_unstable)]
 #![feature(asm)]
 #![feature(box_syntax)]

src/libstd/thread/local.rs

@@ -91,13 +91,13 @@ pub struct LocalKey<T: 'static> {
     //
     // Note that the thunk is itself unsafe because the returned lifetime of the
     // slot where data lives, `'static`, is not actually valid. The lifetime
-    // here is actually `'thread`!
+    // here is actually slightly shorter than the currently running thread!
     //
     // Although this is an extra layer of indirection, it should in theory be
     // trivially devirtualizable by LLVM because the value of `inner` never
     // changes and the constant should be readonly within a crate. This mainly
     // only runs into problems when TLS statics are exported across crates.
-    inner: fn() -> Option<&'static UnsafeCell<Option<T>>>,
+    inner: unsafe fn() -> Option<&'static UnsafeCell<Option<T>>>,
 
     // initialization routine to invoke to create a value
     init: fn() -> T,
@@ -157,12 +157,13 @@ macro_rules! thread_local {
            issue = "0")]
 #[macro_export]
 #[allow_internal_unstable]
+#[cfg_attr(not(stage0), allow_internal_unsafe)]
 macro_rules! __thread_local_inner {
     ($(#[$attr:meta])* $vis:vis $name:ident, $t:ty, $init:expr) => {
         $(#[$attr])* $vis static $name: $crate::thread::LocalKey<$t> = {
             fn __init() -> $t { $init }
 
-            fn __getit() -> $crate::option::Option<
+            unsafe fn __getit() -> $crate::option::Option<
                 &'static $crate::cell::UnsafeCell<
                     $crate::option::Option<$t>>>
             {
@@ -178,7 +179,9 @@ macro_rules! __thread_local_inner {
                 __KEY.get()
             }
 
-            $crate::thread::LocalKey::new(__getit, __init)
+            unsafe {
+                $crate::thread::LocalKey::new(__getit, __init)
+            }
         };
     }
 }
@@ -252,8 +255,8 @@ impl<T: 'static> LocalKey<T> {
     #[unstable(feature = "thread_local_internals",
                reason = "recently added to create a key",
                issue = "0")]
-    pub const fn new(inner: fn() -> Option<&'static UnsafeCell<Option<T>>>,
-                     init: fn() -> T) -> LocalKey<T> {
+    pub const unsafe fn new(inner: unsafe fn() -> Option<&'static UnsafeCell<Option<T>>>,
+                            init: fn() -> T) -> LocalKey<T> {
         LocalKey {
             inner: inner,
             init: init,
@@ -391,6 +394,7 @@ pub mod fast {
         }
     }
 
+    #[cfg(stage0)]
     unsafe impl<T> ::marker::Sync for Key<T> { }
 
     impl<T> Key<T> {
@@ -402,14 +406,12 @@ pub mod fast {
             }
         }
 
-        pub fn get(&'static self) -> Option<&'static UnsafeCell<Option<T>>> {
-            unsafe {
-                if mem::needs_drop::<T>() && self.dtor_running.get() {
-                    return None
-                }
-                self.register_dtor();
+        pub unsafe fn get(&self) -> Option<&'static UnsafeCell<Option<T>>> {
+            if mem::needs_drop::<T>() && self.dtor_running.get() {
+                return None
             }
-            Some(&self.inner)
+            self.register_dtor();
+            Some(&*(&self.inner as *const _))
         }
 
         unsafe fn register_dtor(&self) {
@@ -478,26 +480,24 @@ pub mod os {
             }
         }
 
-        pub fn get(&'static self) -> Option<&'static UnsafeCell<Option<T>>> {
-            unsafe {
-                let ptr = self.os.get() as *mut Value<T>;
-                if !ptr.is_null() {
-                    if ptr as usize == 1 {
-                        return None
-                    }
-                    return Some(&(*ptr).value);
+        pub unsafe fn get(&'static self) -> Option<&'static UnsafeCell<Option<T>>> {
+            let ptr = self.os.get() as *mut Value<T>;
+            if !ptr.is_null() {
+                if ptr as usize == 1 {
+                    return None
                 }
-
-                // If the lookup returned null, we haven't initialized our own
-                // local copy, so do that now.
-                let ptr: Box<Value<T>> = box Value {
-                    key: self,
-                    value: UnsafeCell::new(None),
-                };
-                let ptr = Box::into_raw(ptr);
-                self.os.set(ptr as *mut u8);
-                Some(&(*ptr).value)
+                return Some(&(*ptr).value);
             }
+
+            // If the lookup returned null, we haven't initialized our own
+            // local copy, so do that now.
+            let ptr: Box<Value<T>> = box Value {
+                key: self,
+                value: UnsafeCell::new(None),
+            };
+            let ptr = Box::into_raw(ptr);
+            self.os.set(ptr as *mut u8);
+            Some(&(*ptr).value)
         }
     }
 

src/test/compile-fail/issue-17954.rs

@@ -0,0 +1,25 @@
+// Copyright 2017 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.
+
+#![feature(thread_local)]
+
+#[thread_local]
+static FOO: u8 = 3;
+
+fn main() {
+    let a = &FOO;
+    //~^ ERROR borrowed value does not live long enough
+    //~| does not live long enough
+    //~| NOTE borrowed value must be valid for the static lifetime
+
+    std::thread::spawn(move || {
+        println!("{}", a);
+    });
+} //~ temporary value only lives until here

src/test/compile-fail/issue-43733-2.rs

@@ -0,0 +1,39 @@
+// Copyright 2017 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.
+
+#![feature(const_fn, drop_types_in_const)]
+#![feature(cfg_target_thread_local, thread_local_internals)]
+
+// On platforms *without* `#[thread_local]`, use
+// a custom non-`Sync` type to fake the same error.
+#[cfg(not(target_thread_local))]
+struct Key<T> {
+    _data: std::cell::UnsafeCell<Option<T>>,
+    _flag: std::cell::Cell<bool>,
+}
+
+#[cfg(not(target_thread_local))]
+impl<T> Key<T> {
+    const fn new() -> Self {
+        Key {
+            _data: std::cell::UnsafeCell::new(None),
+            _flag: std::cell::Cell::new(false),
+        }
+    }
+}
+
+#[cfg(target_thread_local)]
+use std::thread::__FastLocalKeyInner as Key;
+
+static __KEY: Key<()> = Key::new();
+//~^ ERROR `std::cell::UnsafeCell<std::option::Option<()>>: std::marker::Sync` is not satisfied
+//~| ERROR `std::cell::Cell<bool>: std::marker::Sync` is not satisfied
+
+fn main() {}

src/test/compile-fail/issue-43733.rs

@@ -0,0 +1,41 @@
+// Copyright 2017 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.
+
+#![feature(const_fn, drop_types_in_const)]
+#![feature(cfg_target_thread_local, thread_local_internals)]
+
+type Foo = std::cell::RefCell<String>;
+
+#[cfg(target_thread_local)]
+static __KEY: std::thread::__FastLocalKeyInner<Foo> =
+    std::thread::__FastLocalKeyInner::new();
+
+#[cfg(not(target_thread_local))]
+static __KEY: std::thread::__OsLocalKeyInner<Foo> =
+    std::thread::__OsLocalKeyInner::new();
+
+fn __getit() -> std::option::Option<
+    &'static std::cell::UnsafeCell<
+        std::option::Option<Foo>>>
+{
+    __KEY.get() //~ ERROR  invocation of unsafe method requires unsafe
+}
+
+static FOO: std::thread::LocalKey<Foo> =
+    std::thread::LocalKey::new(__getit, Default::default);
+//~^ ERROR call to unsafe function requires unsafe
+
+fn main() {
+    FOO.with(|foo| println!("{}", foo.borrow()));
+    std::thread::spawn(|| {
+        FOO.with(|foo| *foo.borrow_mut() += "foo");
+    }).join().unwrap();
+    FOO.with(|foo| println!("{}", foo.borrow()));
+}

src/test/compile-fail/thread-local-in-ctfe.rs

@@ -0,0 +1,38 @@
+// Copyright 2017 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.
+
+#![feature(const_fn, thread_local)]
+
+#[thread_local]
+static A: u32 = 1;
+
+static B: u32 = A;
+//~^ ERROR thread-local statics cannot be accessed at compile-time
+//~| ERROR cannot refer to other statics by value
+//~| WARN non-constant path in constant expression
+
+static C: &u32 = &A;
+//~^ ERROR thread-local statics cannot be accessed at compile-time
+
+const D: u32 = A;
+//~^ ERROR thread-local statics cannot be accessed at compile-time
+//~| ERROR cannot refer to statics by value
+//~| WARN non-constant path in constant expression
+
+const E: &u32 = &A;
+//~^ ERROR thread-local statics cannot be accessed at compile-time
+
+const fn f() -> u32 {
+    A
+    //~^ ERROR thread-local statics cannot be accessed at compile-time
+    //~| ERROR cannot refer to statics by value
+}
+
+fn main() {}

src/test/run-pass/auxiliary/thread-local-extern-static.rs

@@ -8,10 +8,13 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-#![feature(thread_local)]
-#![feature(cfg_target_thread_local)]
+#![feature(cfg_target_thread_local, const_fn, thread_local)]
 #![crate_type = "lib"]
 
+#[cfg(target_thread_local)]
+use std::cell::Cell;
+
 #[no_mangle]
-#[cfg_attr(target_thread_local, thread_local)]
-pub static FOO: u32 = 3;
+#[cfg(target_thread_local)]
+#[thread_local]
+pub static FOO: Cell<u32> = Cell::new(3);