Rollup merge of rust-lang#71712 - RalfJung:error-backtrace, r=oli-obk

Miri: port error backtraces to std::backtrace

No need to pull in an external dependency if libstd already includes this feature (using the same dependency internally, but... still).

r? @oli-obk

Author: RalfJung

Cargo.lock

@@ -3978,7 +3978,6 @@ name = "rustc_middle"
 version = "0.0.0"
 dependencies = [
  "arena",
- "backtrace",
  "bitflags",
  "byteorder",
  "log",

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"

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)]

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
             }
         };

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();