cleanup tcx usage and a few comments

Author: RalfJung

src/shims/foreign_items.rs

@@ -124,7 +124,7 @@ pub trait EvalContextExt<'mir, 'tcx: 'mir>: crate::MiriEvalContextExt<'mir, 'tcx
         };
         // Strip linker suffixes (seen on 32-bit macOS).
         let link_name = link_name.trim_end_matches("$UNIX2003");
-        let tcx = &{ this.tcx.tcx };
+        let tcx = this.tcx.tcx;
 
         // First: functions that diverge.
         let (dest, ret) = match ret {
@@ -133,8 +133,8 @@ pub trait EvalContextExt<'mir, 'tcx: 'mir>: crate::MiriEvalContextExt<'mir, 'tcx
                 // The implementation is provided by the function with the `#[panic_handler]` attribute.
                 "panic_impl" => {
                     this.check_panic_supported()?;
-                    let panic_impl_id = this.tcx.lang_items().panic_impl().unwrap();
-                    let panic_impl_instance = ty::Instance::mono(*this.tcx, panic_impl_id);
+                    let panic_impl_id = tcx.lang_items().panic_impl().unwrap();
+                    let panic_impl_instance = ty::Instance::mono(tcx, panic_impl_id);
                     return Ok(Some(&*this.load_mir(panic_impl_instance.def, None)?));
                 }
                 | "exit"

src/shims/foreign_items/posix.rs

@@ -17,7 +17,6 @@ pub trait EvalContextExt<'mir, 'tcx: 'mir>: crate::MiriEvalContextExt<'mir, 'tcx
         ret: mir::BasicBlock,
     ) -> InterpResult<'tcx, bool> {
         let this = self.eval_context_mut();
-        let tcx = &{ this.tcx.tcx };
 
         match link_name {
             // Environment related shims
@@ -65,7 +64,7 @@ pub trait EvalContextExt<'mir, 'tcx: 'mir>: crate::MiriEvalContextExt<'mir, 'tcx
             "write" => {
                 let fd = this.read_scalar(args[0])?.to_i32()?;
                 let buf = this.read_scalar(args[1])?.not_undef()?;
-                let n = this.read_scalar(args[2])?.to_machine_usize(tcx)?;
+                let n = this.read_scalar(args[2])?.to_machine_usize(this)?;
                 trace!("Called write({:?}, {:?}, {:?})", fd, buf, n);
                 let result = if fd == 1 || fd == 2 {
                     // stdout/stderr
@@ -209,7 +208,7 @@ pub trait EvalContextExt<'mir, 'tcx: 'mir>: crate::MiriEvalContextExt<'mir, 'tcx
             }
             "pthread_getspecific" => {
                 let key = this.force_bits(this.read_scalar(args[0])?.not_undef()?, args[0].layout.size)?;
-                let ptr = this.machine.tls.load_tls(key, tcx)?;
+                let ptr = this.machine.tls.load_tls(key, this)?;
                 this.write_scalar(ptr, dest)?;
             }
             "pthread_setspecific" => {

src/shims/foreign_items/windows.rs

@@ -13,7 +13,6 @@ pub trait EvalContextExt<'mir, 'tcx: 'mir>: crate::MiriEvalContextExt<'mir, 'tcx
         _ret: mir::BasicBlock,
     ) -> InterpResult<'tcx, bool> {
         let this = self.eval_context_mut();
-        let tcx = &{ this.tcx.tcx };
 
         match link_name {
             // Windows API stubs.
@@ -160,7 +159,7 @@ pub trait EvalContextExt<'mir, 'tcx: 'mir>: crate::MiriEvalContextExt<'mir, 'tcx
             }
             "TlsGetValue" => {
                 let key = u128::from(this.read_scalar(args[0])?.to_u32()?);
-                let ptr = this.machine.tls.load_tls(key, tcx)?;
+                let ptr = this.machine.tls.load_tls(key, this)?;
                 this.write_scalar(ptr, dest)?;
             }
             "TlsSetValue" => {

src/shims/intrinsics.rs

@@ -24,13 +24,12 @@ pub trait EvalContextExt<'mir, 'tcx: 'mir>: crate::MiriEvalContextExt<'mir, 'tcx
         if this.emulate_intrinsic(span, instance, args, ret)? {
             return Ok(());
         }
-        let tcx = &{ this.tcx.tcx };
         let substs = instance.substs;
 
         // All these intrinsics take raw pointers, so if we access memory directly
         // (as opposed to through a place), we have to remember to erase any tag
         // that might still hang around!
-        let intrinsic_name = &*tcx.item_name(instance.def_id()).as_str();
+        let intrinsic_name = &*this.tcx.item_name(instance.def_id()).as_str();
 
         // First handle intrinsics without return place.
         let (dest, ret) = match ret {

src/shims/tls.rs

@@ -70,7 +70,7 @@ impl<'tcx> TlsData<'tcx> {
     }
 
     pub fn load_tls(
-        &mut self,
+        &self,
         key: TlsKey,
         cx: &impl HasDataLayout,
     ) -> InterpResult<'tcx, Scalar<Tag>> {
@@ -107,7 +107,8 @@ impl<'tcx> TlsData<'tcx> {
         Ok(())
     }
 
-    /// Returns a dtor, its argument and its index, if one is supposed to run
+    /// Returns a dtor, its argument and its index, if one is supposed to run.
+    /// `key` is the last dtors that was run; we return the *next* one after that.
     ///
     /// An optional destructor function may be associated with each key value.
     /// At thread exit, if a key value has a non-NULL destructor pointer,
@@ -191,8 +192,10 @@ pub trait EvalContextExt<'mir, 'tcx: 'mir>: crate::MiriEvalContextExt<'mir, 'tcx
             // step until out of stackframes
             this.run()?;
 
+            // Fetch next dtor after `key`.
             dtor = match this.machine.tls.fetch_tls_dtor(Some(key)) {
                 dtor @ Some(_) => dtor,
+                // We ran each dtor once, start over from the beginning.
                 None => this.machine.tls.fetch_tls_dtor(None),
             };
         }