diff --git a/Cargo.lock b/Cargo.lock
index 13a130a1b49c0..8bd1e5f3308b4 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -3978,7 +3978,6 @@ name = "rustc_middle"
 version = "0.0.0"
 dependencies = [
  "arena",
- "backtrace",
  "bitflags",
  "byteorder",
  "log",
diff --git a/src/librustc_codegen_ssa/mir/constant.rs b/src/librustc_codegen_ssa/mir/constant.rs
index 298aa25f0321f..d2629b771c2af 100644
--- a/src/librustc_codegen_ssa/mir/constant.rs
+++ b/src/librustc_codegen_ssa/mir/constant.rs
@@ -16,25 +16,9 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
         bx: &mut Bx,
         constant: &mir::Constant<'tcx>,
     ) -> Result<OperandRef<'tcx, Bx::Value>, ErrorHandled> {
-        match constant.literal.val {
-            // Special case unevaluated statics, because statics have an identity and thus should
-            // use `get_static` to get at their id.
-            // FIXME(oli-obk): can we unify this somehow, maybe by making const eval of statics
-            // always produce `&STATIC`. This may also simplify how const eval works with statics.
-            ty::ConstKind::Unevaluated(def_id, substs, None) if self.cx.tcx().is_static(def_id) => {
-                assert!(substs.is_empty(), "we don't support generic statics yet");
-                let static_ = bx.get_static(def_id);
-                // we treat operands referring to statics as if they were `&STATIC` instead
-                let ptr_ty = self.cx.tcx().mk_mut_ptr(self.monomorphize(&constant.literal.ty));
-                let layout = bx.layout_of(ptr_ty);
-                Ok(OperandRef::from_immediate_or_packed_pair(bx, static_, layout))
-            }
-            _ => {
-                let val = self.eval_mir_constant(constant)?;
-                let ty = self.monomorphize(&constant.literal.ty);
-                Ok(OperandRef::from_const(bx, val, ty))
-            }
-        }
+        let val = self.eval_mir_constant(constant)?;
+        let ty = self.monomorphize(&constant.literal.ty);
+        Ok(OperandRef::from_const(bx, val, ty))
     }
 
     pub fn eval_mir_constant(
diff --git a/src/librustc_middle/Cargo.toml b/src/librustc_middle/Cargo.toml
index 8e27e03ea4ffe..398ba4d72d449 100644
--- a/src/librustc_middle/Cargo.toml
+++ b/src/librustc_middle/Cargo.toml
@@ -30,7 +30,6 @@ rustc_index = { path = "../librustc_index" }
 rustc_serialize = { path = "../libserialize", package = "serialize" }
 rustc_ast = { path = "../librustc_ast" }
 rustc_span = { path = "../librustc_span" }
-backtrace = "0.3.40"
 byteorder = { version = "1.3" }
 smallvec = { version = "1.0", features = ["union", "may_dangle"] }
 measureme = "0.7.1"
diff --git a/src/librustc_middle/lib.rs b/src/librustc_middle/lib.rs
index 4ed03fd21ad18..9b38b43c93ae2 100644
--- a/src/librustc_middle/lib.rs
+++ b/src/librustc_middle/lib.rs
@@ -23,6 +23,7 @@
 //! This API is completely unstable and subject to change.
 
 #![doc(html_root_url = "https://doc.rust-lang.org/nightly/")]
+#![feature(backtrace)]
 #![feature(bool_to_option)]
 #![feature(box_patterns)]
 #![feature(box_syntax)]
diff --git a/src/librustc_middle/mir/interpret/error.rs b/src/librustc_middle/mir/interpret/error.rs
index 40454ce3b2db8..4b88467ac110f 100644
--- a/src/librustc_middle/mir/interpret/error.rs
+++ b/src/librustc_middle/mir/interpret/error.rs
@@ -6,7 +6,6 @@ use crate::ty::query::TyCtxtAt;
 use crate::ty::tls;
 use crate::ty::{self, layout, Ty};
 
-use backtrace::Backtrace;
 use rustc_data_structures::sync::Lock;
 use rustc_errors::{struct_span_err, DiagnosticBuilder, ErrorReported};
 use rustc_hir as hir;
@@ -15,7 +14,7 @@ use rustc_macros::HashStable;
 use rustc_session::CtfeBacktrace;
 use rustc_span::{def_id::DefId, Pos, Span};
 use rustc_target::abi::{Align, Size};
-use std::{any::Any, fmt, mem};
+use std::{any::Any, backtrace::Backtrace, fmt, mem};
 
 #[derive(Debug, Copy, Clone, PartialEq, Eq, HashStable, RustcEncodable, RustcDecodable)]
 pub enum ErrorHandled {
@@ -219,16 +218,15 @@ impl fmt::Display for InterpErrorInfo<'_> {
 }
 
 impl InterpErrorInfo<'_> {
-    pub fn print_backtrace(&mut self) {
-        if let Some(ref mut backtrace) = self.backtrace {
-            print_backtrace(&mut *backtrace);
+    pub fn print_backtrace(&self) {
+        if let Some(backtrace) = self.backtrace.as_ref() {
+            print_backtrace(backtrace);
         }
     }
 }
 
-fn print_backtrace(backtrace: &mut Backtrace) {
-    backtrace.resolve();
-    eprintln!("\n\nAn error occurred in miri:\n{:?}", backtrace);
+fn print_backtrace(backtrace: &Backtrace) {
+    eprintln!("\n\nAn error occurred in miri:\n{}", backtrace);
 }
 
 impl From<ErrorHandled> for InterpErrorInfo<'_> {
@@ -255,11 +253,11 @@ impl<'tcx> From<InterpError<'tcx>> for InterpErrorInfo<'tcx> {
 
         let backtrace = match capture_backtrace {
             CtfeBacktrace::Disabled => None,
-            CtfeBacktrace::Capture => Some(Box::new(Backtrace::new_unresolved())),
+            CtfeBacktrace::Capture => Some(Box::new(Backtrace::force_capture())),
             CtfeBacktrace::Immediate => {
                 // Print it now.
-                let mut backtrace = Backtrace::new_unresolved();
-                print_backtrace(&mut backtrace);
+                let backtrace = Backtrace::force_capture();
+                print_backtrace(&backtrace);
                 None
             }
         };
@@ -439,10 +437,10 @@ impl fmt::Display for UndefinedBehaviorInfo {
             DerefFunctionPointer(a) => write!(f, "accessing {} which contains a function", a),
             ValidationFailure(ref err) => write!(f, "type validation failed: {}", err),
             InvalidBool(b) => {
-                write!(f, "interpreting an invalid 8-bit value as a bool: 0x{:2x}", b)
+                write!(f, "interpreting an invalid 8-bit value as a bool: 0x{:02x}", b)
             }
             InvalidChar(c) => {
-                write!(f, "interpreting an invalid 32-bit value as a char: 0x{:8x}", c)
+                write!(f, "interpreting an invalid 32-bit value as a char: 0x{:08x}", c)
             }
             InvalidDiscriminant(val) => write!(f, "enum value has invalid discriminant: {}", val),
             InvalidFunctionPointer(p) => {
diff --git a/src/librustc_mir/const_eval/error.rs b/src/librustc_mir/const_eval/error.rs
index 3c3618f390c61..b165a69433db1 100644
--- a/src/librustc_mir/const_eval/error.rs
+++ b/src/librustc_mir/const_eval/error.rs
@@ -52,7 +52,7 @@ impl Error for ConstEvalErrKind {}
 /// Should be called only if the error is actually going to to be reported!
 pub fn error_to_const_error<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>>(
     ecx: &InterpCx<'mir, 'tcx, M>,
-    mut error: InterpErrorInfo<'tcx>,
+    error: InterpErrorInfo<'tcx>,
 ) -> ConstEvalErr<'tcx> {
     error.print_backtrace();
     let stacktrace = ecx.generate_stacktrace();
diff --git a/src/librustc_trait_selection/traits/util.rs b/src/librustc_trait_selection/traits/util.rs
index 4aceccf64ce65..eff73cf4a2d8a 100644
--- a/src/librustc_trait_selection/traits/util.rs
+++ b/src/librustc_trait_selection/traits/util.rs
@@ -217,7 +217,6 @@ pub fn impl_trait_ref_and_oblig<'a, 'tcx>(
     (impl_trait_ref, impl_obligations)
 }
 
-/// See [`super::obligations_for_generics`].
 pub fn predicates_for_generics<'tcx>(
     cause: ObligationCause<'tcx>,
     recursion_depth: usize,
diff --git a/src/test/ui/process-termination/process-termination-blocking-io.rs b/src/test/ui/process-termination/process-termination-blocking-io.rs
new file mode 100644
index 0000000000000..864fb776e867d
--- /dev/null
+++ b/src/test/ui/process-termination/process-termination-blocking-io.rs
@@ -0,0 +1,19 @@
+// program should terminate even if a thread is blocked on I/O.
+// https://github.com/fortanix/rust-sgx/issues/109
+
+// run-pass
+// ignore-wasm no threads support
+
+use std::{net::TcpListener, sync::mpsc, thread};
+
+fn main() {
+    let (tx, rx) = mpsc::channel();
+    thread::spawn(move || {
+        let listen = TcpListener::bind("0:0").unwrap();
+        tx.send(()).unwrap();
+        while let Ok(_) = listen.accept() {}
+    });
+    rx.recv().unwrap();
+    for _ in 0..3 { thread::yield_now(); }
+    println!("Exiting main thread");
+}
diff --git a/src/test/ui/process-termination/process-termination-simple.rs b/src/test/ui/process-termination/process-termination-simple.rs
new file mode 100644
index 0000000000000..3660f95b05bc1
--- /dev/null
+++ b/src/test/ui/process-termination/process-termination-simple.rs
@@ -0,0 +1,13 @@
+// program should terminate when std::process::exit is called from any thread
+
+// run-pass
+// ignore-wasm no threads support
+
+use std::{process, thread};
+
+fn main() {
+    let h = thread::spawn(|| {
+        process::exit(0);
+    });
+    let _ = h.join();
+}