run Windows TLS dtor function

Author: RalfJung

src/eval.rs

@@ -184,10 +184,9 @@ pub fn create_ecx<'mir, 'tcx: 'mir>(
 /// Returns `Some(return_code)` if program executed completed.
 /// Returns `None` if an evaluation error occured.
 pub fn eval_main<'tcx>(tcx: TyCtxt<'tcx>, main_id: DefId, config: MiriConfig) -> Option<i64> {
-    // FIXME: We always ignore leaks on some OSs where we do not
-    // correctly implement TLS destructors.
-    let target_os = &tcx.sess.target.target.target_os;
-    let ignore_leaks = config.ignore_leaks || target_os == "windows";
+    // FIXME: on Windows, locks and TLS dtor management allocate and leave that memory in `static`s.
+    // So we need https://github.com/rust-lang/miri/issues/940 to fix the leaks there.
+    let ignore_leaks = config.ignore_leaks || tcx.sess.target.target.target_os == "windows";
 
     let (mut ecx, ret_place) = match create_ecx(tcx, main_id, config) {
         Ok(v) => v,

src/helpers.rs

@@ -413,7 +413,7 @@ pub trait EvalContextExt<'mir, 'tcx: 'mir>: crate::MiriEvalContextExt<'mir, 'tcx
     fn set_last_error_from_io_error(&mut self, e: std::io::Error) -> InterpResult<'tcx> {
         use std::io::ErrorKind::*;
         let this = self.eval_context_mut();
-        let target = &this.tcx.tcx.sess.target.target;
+        let target = &this.tcx.sess.target.target;
         let last_error = if target.options.target_family == Some("unix".to_owned()) {
             this.eval_libc(match e.kind() {
                 ConnectionRefused => "ECONNREFUSED",

src/machine.rs

@@ -102,6 +102,20 @@ impl MemoryExtra {
         }
     }
 
+    fn add_extern_static<'tcx, 'mir>(
+        this: &mut MiriEvalContext<'mir, 'tcx>,
+        name: &str,
+        ptr: Scalar<Tag>,
+    ) {
+        let ptr = ptr.assert_ptr();
+        assert_eq!(ptr.offset, Size::ZERO);
+        this.memory
+            .extra
+            .extern_statics
+            .insert(Symbol::intern(name), ptr.alloc_id)
+            .unwrap_none();
+    }
+
     /// Sets up the "extern statics" for this machine.
     pub fn init_extern_statics<'tcx, 'mir>(
         this: &mut MiriEvalContext<'mir, 'tcx>,
@@ -113,17 +127,17 @@ impl MemoryExtra {
                 let layout = this.layout_of(this.tcx.types.usize)?;
                 let place = this.allocate(layout, MiriMemoryKind::Machine.into());
                 this.write_scalar(Scalar::from_machine_usize(0, &*this.tcx), place.into())?;
-                this.memory
-                    .extra
-                    .extern_statics
-                    .insert(Symbol::intern("__cxa_thread_atexit_impl"), place.ptr.assert_ptr().alloc_id)
-                    .unwrap_none();
+                Self::add_extern_static(this, "__cxa_thread_atexit_impl", place.ptr);
                 // "environ"
-                this.memory
-                    .extra
-                    .extern_statics
-                    .insert(Symbol::intern("environ"), this.machine.env_vars.environ.unwrap().ptr.assert_ptr().alloc_id)
-                    .unwrap_none();
+                Self::add_extern_static(this, "environ", this.machine.env_vars.environ.unwrap().ptr);
+            }
+            "windows" => {
+                // "_tls_used"
+                // This is some obscure hack that is part of the Windows TLS story. It's a `u8`.
+                let layout = this.layout_of(this.tcx.types.u8)?;
+                let place = this.allocate(layout, MiriMemoryKind::Machine.into());
+                this.write_scalar(Scalar::from_u8(0), place.into())?;
+                Self::add_extern_static(this, "_tls_used", place.ptr);
             }
             _ => {} // No "extern statics" supported on this target
         }

src/shims/foreign_items.rs

@@ -19,7 +19,7 @@ pub trait EvalContextExt<'mir, 'tcx: 'mir>: crate::MiriEvalContextExt<'mir, 'tcx
     fn min_align(&self, size: u64, kind: MiriMemoryKind) -> Align {
         let this = self.eval_context_ref();
         // List taken from `libstd/sys_common/alloc.rs`.
-        let min_align = match this.tcx.tcx.sess.target.target.arch.as_str() {
+        let min_align = match this.tcx.sess.target.target.arch.as_str() {
             "x86" | "arm" | "mips" | "powerpc" | "powerpc64" | "asmjs" | "wasm32" => 8,
             "x86_64" | "aarch64" | "mips64" | "s390x" | "sparc64" => 16,
             arch => bug!("Unsupported target architecture: {}", arch),

src/shims/tls.rs

@@ -159,6 +159,32 @@ pub trait EvalContextExt<'mir, 'tcx: 'mir>: crate::MiriEvalContextExt<'mir, 'tcx
         assert!(!this.machine.tls.dtors_running, "running TLS dtors twice");
         this.machine.tls.dtors_running = true;
 
+        if this.tcx.sess.target.target.target_os == "windows" {
+            // Windows has a special magic linker section that is run on certain events.
+            // Instead of searching for that section and supporting arbitrary hooks in there
+            // (that would be basically https://github.com/rust-lang/miri/issues/450),
+            // we specifically look up the static in libstd that we know is placed
+            // in that section.
+            let thread_callback = this.eval_path_scalar(&["std", "sys", "windows", "thread_local", "p_thread_callback"])?;
+            let thread_callback = this.memory.get_fn(thread_callback.not_undef()?)?.as_instance()?;
+
+            // The signature of this function is `unsafe extern "system" fn(h: c::LPVOID, dwReason: c::DWORD, pv: c::LPVOID)`.
+            let reason = this.eval_path_scalar(&["std", "sys", "windows", "c", "DLL_PROCESS_DETACH"])?;
+            let ret_place = MPlaceTy::dangling(this.layout_of(this.tcx.mk_unit())?, this).into();
+            this.call_function(
+                thread_callback,
+                &[Scalar::ptr_null(this).into(), reason.into(), Scalar::ptr_null(this).into()],
+                Some(ret_place),
+                StackPopCleanup::None { cleanup: true },
+            )?;
+
+            // step until out of stackframes
+            this.run()?;
+
+            // Windows doesn't have other destructors.
+            return Ok(());
+        }
+
         // The macOS global dtor runs "before any TLS slots get freed", so do that first.
         if let Some((instance, data)) = this.machine.tls.global_dtor {
             trace!("Running global dtor {:?} on {:?}", instance, data);
@@ -199,7 +225,6 @@ pub trait EvalContextExt<'mir, 'tcx: 'mir>: crate::MiriEvalContextExt<'mir, 'tcx
                 None => this.machine.tls.fetch_tls_dtor(None),
             };
         }
-        // FIXME: On a windows target, call `unsafe extern "system" fn on_tls_callback`.
         Ok(())
     }
 }