Auto merge of #60026 - Aaron1011:feature/miri-unwind, r=RalfJung,oli-obk

Add hooks for Miri panic unwinding

This commits adds in some additional hooks to allow Miri to properly
handle panic unwinding. None of this should have any impact on CTFE mode

This supports https://github.com/rust-lang/miri/pull/693

1 files changed, 8 insertions, 1 deletions

diff --git a/src/libstd/sys_common/backtrace.rs b/src/libstd/sys_common/backtrace.rs
index 9c406ec39cc..d7296b43fbe 100644
--- a/src/libstd/sys_common/backtrace.rs
+++ b/src/libstd/sys_common/backtrace.rs
@@ -66,7 +66,14 @@ unsafe fn _print(w: &mut dyn Write, format: PrintFmt) -> io::Result<()> {
 }
 
 unsafe fn _print_fmt(fmt: &mut fmt::Formatter<'_>, print_fmt: PrintFmt) -> fmt::Result {
-    let cwd = env::current_dir().ok();
+    // Always 'fail' to get the cwd when running under Miri -
+    // this allows Miri to display backtraces in isolation mode
+    let cwd = if !cfg!(miri) {
+        env::current_dir().ok()
+    } else {
+        None
+    };
+
     let mut print_path = move |fmt: &mut fmt::Formatter<'_>, bows: BytesOrWideString<'_>| {
         output_filename(fmt, bows, print_fmt, cwd.as_ref())
     };