From 3e633981ef0827bf699559036f1437bca071f804 Mon Sep 17 00:00:00 2001
From: Ralf Jung <post@ralfj.de>
Date: Thu, 18 Apr 2024 11:14:37 +0200
Subject: [PATCH] when suggesting RUST_BACKTRACE=1, add a special note for
 Miri's env var isolation

---
 library/std/src/panicking.rs                               | 7 +++++++
 .../fail/function_calls/exported_symbol_bad_unwind1.stderr | 1 +
 .../function_calls/exported_symbol_bad_unwind2.both.stderr | 1 +
 .../exported_symbol_bad_unwind2.definition.stderr          | 1 +
 .../exported_symbol_bad_unwind2.extern_block.stderr        | 1 +
 .../fail/function_calls/return_pointer_on_unwind.stderr    | 1 +
 .../tests/fail/intrinsics/uninit_uninhabited_type.stderr   | 1 +
 src/tools/miri/tests/fail/intrinsics/zero_fn_ptr.stderr    | 1 +
 src/tools/miri/tests/fail/panic/bad_unwind.stderr          | 1 +
 src/tools/miri/tests/fail/panic/double_panic.stderr        | 1 +
 src/tools/miri/tests/fail/panic/panic_abort1.stderr        | 1 +
 src/tools/miri/tests/fail/panic/panic_abort2.stderr        | 1 +
 src/tools/miri/tests/fail/panic/panic_abort3.stderr        | 1 +
 src/tools/miri/tests/fail/panic/panic_abort4.stderr        | 1 +
 src/tools/miri/tests/fail/terminate-terminator.stderr      | 1 +
 src/tools/miri/tests/fail/unwind-action-terminate.stderr   | 1 +
 src/tools/miri/tests/panic/div-by-zero-2.stderr            | 1 +
 .../function_calls/exported_symbol_good_unwind.stderr      | 1 +
 src/tools/miri/tests/panic/oob_subslice.stderr             | 1 +
 src/tools/miri/tests/panic/overflowing-lsh-neg.stderr      | 1 +
 src/tools/miri/tests/panic/overflowing-rsh-1.stderr        | 1 +
 src/tools/miri/tests/panic/overflowing-rsh-2.stderr        | 1 +
 src/tools/miri/tests/panic/panic2.stderr                   | 1 +
 src/tools/miri/tests/panic/panic3.stderr                   | 1 +
 src/tools/miri/tests/panic/panic4.stderr                   | 1 +
 src/tools/miri/tests/panic/transmute_fat2.stderr           | 1 +
 .../miri/tests/panic/unsupported_foreign_function.stderr   | 1 +
 src/tools/miri/tests/panic/unsupported_syscall.stderr      | 1 +
 src/tools/miri/tests/pass/panic/catch_panic.stderr         | 1 +
 src/tools/miri/tests/pass/panic/concurrent-panic.stderr    | 1 +
 src/tools/miri/tests/pass/panic/nested_panic_caught.stderr | 1 +
 src/tools/miri/tests/pass/panic/thread_panic.stderr        | 1 +
 32 files changed, 38 insertions(+)

diff --git a/library/std/src/panicking.rs b/library/std/src/panicking.rs
index 0052fcbb94a81..5699937cdb49b 100644
--- a/library/std/src/panicking.rs
+++ b/library/std/src/panicking.rs
@@ -277,6 +277,13 @@ fn default_hook(info: &PanicInfo<'_>) {
                         "note: run with `RUST_BACKTRACE=1` environment variable to display a \
                              backtrace"
                     );
+                    if cfg!(miri) {
+                        let _ = writeln!(
+                            err,
+                            "note: in Miri, you may have to set `-Zmiri-env-forward=RUST_BACKTRACE` \
+                                for the environment variable to have an effect"
+                        );
+                    }
                 }
             }
             // If backtraces aren't supported or are forced-off, do nothing.
diff --git a/src/tools/miri/tests/fail/function_calls/exported_symbol_bad_unwind1.stderr b/src/tools/miri/tests/fail/function_calls/exported_symbol_bad_unwind1.stderr
index ab32883a03562..42beed4ecdec3 100644
--- a/src/tools/miri/tests/fail/function_calls/exported_symbol_bad_unwind1.stderr
+++ b/src/tools/miri/tests/fail/function_calls/exported_symbol_bad_unwind1.stderr
@@ -1,6 +1,7 @@
 thread 'main' panicked at $DIR/exported_symbol_bad_unwind1.rs:LL:CC:
 explicit panic
 note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace
+note: in Miri, you may have to set `-Zmiri-env-forward=RUST_BACKTRACE` for the environment variable to have an effect
 error: Undefined Behavior: unwinding past a stack frame that does not allow unwinding
   --> $DIR/exported_symbol_bad_unwind1.rs:LL:CC
    |
diff --git a/src/tools/miri/tests/fail/function_calls/exported_symbol_bad_unwind2.both.stderr b/src/tools/miri/tests/fail/function_calls/exported_symbol_bad_unwind2.both.stderr
index 9774e1e1a793b..d88781ed22549 100644
--- a/src/tools/miri/tests/fail/function_calls/exported_symbol_bad_unwind2.both.stderr
+++ b/src/tools/miri/tests/fail/function_calls/exported_symbol_bad_unwind2.both.stderr
@@ -1,6 +1,7 @@
 thread 'main' panicked at $DIR/exported_symbol_bad_unwind2.rs:LL:CC:
 explicit panic
 note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace
+note: in Miri, you may have to set `-Zmiri-env-forward=RUST_BACKTRACE` for the environment variable to have an effect
 thread 'main' panicked at RUSTLIB/core/src/panicking.rs:LL:CC:
 panic in a function that cannot unwind
 stack backtrace:
diff --git a/src/tools/miri/tests/fail/function_calls/exported_symbol_bad_unwind2.definition.stderr b/src/tools/miri/tests/fail/function_calls/exported_symbol_bad_unwind2.definition.stderr
index 9774e1e1a793b..d88781ed22549 100644
--- a/src/tools/miri/tests/fail/function_calls/exported_symbol_bad_unwind2.definition.stderr
+++ b/src/tools/miri/tests/fail/function_calls/exported_symbol_bad_unwind2.definition.stderr
@@ -1,6 +1,7 @@
 thread 'main' panicked at $DIR/exported_symbol_bad_unwind2.rs:LL:CC:
 explicit panic
 note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace
+note: in Miri, you may have to set `-Zmiri-env-forward=RUST_BACKTRACE` for the environment variable to have an effect
 thread 'main' panicked at RUSTLIB/core/src/panicking.rs:LL:CC:
 panic in a function that cannot unwind
 stack backtrace:
diff --git a/src/tools/miri/tests/fail/function_calls/exported_symbol_bad_unwind2.extern_block.stderr b/src/tools/miri/tests/fail/function_calls/exported_symbol_bad_unwind2.extern_block.stderr
index f89cee0b86332..bc3e4858716e3 100644
--- a/src/tools/miri/tests/fail/function_calls/exported_symbol_bad_unwind2.extern_block.stderr
+++ b/src/tools/miri/tests/fail/function_calls/exported_symbol_bad_unwind2.extern_block.stderr
@@ -1,6 +1,7 @@
 thread 'main' panicked at $DIR/exported_symbol_bad_unwind2.rs:LL:CC:
 explicit panic
 note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace
+note: in Miri, you may have to set `-Zmiri-env-forward=RUST_BACKTRACE` for the environment variable to have an effect
 error: Undefined Behavior: unwinding past a stack frame that does not allow unwinding
   --> $DIR/exported_symbol_bad_unwind2.rs:LL:CC
    |
diff --git a/src/tools/miri/tests/fail/function_calls/return_pointer_on_unwind.stderr b/src/tools/miri/tests/fail/function_calls/return_pointer_on_unwind.stderr
index 7f035eb5e8575..a2fa4c1d590d0 100644
--- a/src/tools/miri/tests/fail/function_calls/return_pointer_on_unwind.stderr
+++ b/src/tools/miri/tests/fail/function_calls/return_pointer_on_unwind.stderr
@@ -1,6 +1,7 @@
 thread 'main' panicked at $DIR/return_pointer_on_unwind.rs:LL:CC:
 explicit panic
 note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace
+note: in Miri, you may have to set `-Zmiri-env-forward=RUST_BACKTRACE` for the environment variable to have an effect
 error: Undefined Behavior: using uninitialized data, but this operation requires initialized memory
   --> $DIR/return_pointer_on_unwind.rs:LL:CC
    |
diff --git a/src/tools/miri/tests/fail/intrinsics/uninit_uninhabited_type.stderr b/src/tools/miri/tests/fail/intrinsics/uninit_uninhabited_type.stderr
index 4723eddaa67be..447f7cae6ce9d 100644
--- a/src/tools/miri/tests/fail/intrinsics/uninit_uninhabited_type.stderr
+++ b/src/tools/miri/tests/fail/intrinsics/uninit_uninhabited_type.stderr
@@ -1,6 +1,7 @@
 thread 'main' panicked at RUSTLIB/core/src/panicking.rs:LL:CC:
 aborted execution: attempted to instantiate uninhabited type `!`
 note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace
+note: in Miri, you may have to set `-Zmiri-env-forward=RUST_BACKTRACE` for the environment variable to have an effect
 thread caused non-unwinding panic. aborting.
 error: abnormal termination: the program aborted execution
   --> RUSTLIB/std/src/sys/pal/PLATFORM/mod.rs:LL:CC
diff --git a/src/tools/miri/tests/fail/intrinsics/zero_fn_ptr.stderr b/src/tools/miri/tests/fail/intrinsics/zero_fn_ptr.stderr
index 9c6dd10079edb..bae34149807fc 100644
--- a/src/tools/miri/tests/fail/intrinsics/zero_fn_ptr.stderr
+++ b/src/tools/miri/tests/fail/intrinsics/zero_fn_ptr.stderr
@@ -1,6 +1,7 @@
 thread 'main' panicked at RUSTLIB/core/src/panicking.rs:LL:CC:
 aborted execution: attempted to zero-initialize type `fn()`, which is invalid
 note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace
+note: in Miri, you may have to set `-Zmiri-env-forward=RUST_BACKTRACE` for the environment variable to have an effect
 thread caused non-unwinding panic. aborting.
 error: abnormal termination: the program aborted execution
   --> RUSTLIB/std/src/sys/pal/PLATFORM/mod.rs:LL:CC
diff --git a/src/tools/miri/tests/fail/panic/bad_unwind.stderr b/src/tools/miri/tests/fail/panic/bad_unwind.stderr
index e4af01feb8d7a..230e8337c7cd1 100644
--- a/src/tools/miri/tests/fail/panic/bad_unwind.stderr
+++ b/src/tools/miri/tests/fail/panic/bad_unwind.stderr
@@ -1,6 +1,7 @@
 thread 'main' panicked at $DIR/bad_unwind.rs:LL:CC:
 explicit panic
 note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace
+note: in Miri, you may have to set `-Zmiri-env-forward=RUST_BACKTRACE` for the environment variable to have an effect
 error: Undefined Behavior: unwinding past a stack frame that does not allow unwinding
   --> $DIR/bad_unwind.rs:LL:CC
    |
diff --git a/src/tools/miri/tests/fail/panic/double_panic.stderr b/src/tools/miri/tests/fail/panic/double_panic.stderr
index e3cacbd27bac6..3b7a1511fa0b6 100644
--- a/src/tools/miri/tests/fail/panic/double_panic.stderr
+++ b/src/tools/miri/tests/fail/panic/double_panic.stderr
@@ -1,6 +1,7 @@
 thread 'main' panicked at $DIR/double_panic.rs:LL:CC:
 first
 note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace
+note: in Miri, you may have to set `-Zmiri-env-forward=RUST_BACKTRACE` for the environment variable to have an effect
 thread 'main' panicked at $DIR/double_panic.rs:LL:CC:
 second
 stack backtrace:
diff --git a/src/tools/miri/tests/fail/panic/panic_abort1.stderr b/src/tools/miri/tests/fail/panic/panic_abort1.stderr
index 60455693619f3..7694cc70b227a 100644
--- a/src/tools/miri/tests/fail/panic/panic_abort1.stderr
+++ b/src/tools/miri/tests/fail/panic/panic_abort1.stderr
@@ -1,6 +1,7 @@
 thread 'main' panicked at $DIR/panic_abort1.rs:LL:CC:
 panicking from libstd
 note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace
+note: in Miri, you may have to set `-Zmiri-env-forward=RUST_BACKTRACE` for the environment variable to have an effect
 error: abnormal termination: the program aborted execution
   --> RUSTLIB/panic_abort/src/lib.rs:LL:CC
    |
diff --git a/src/tools/miri/tests/fail/panic/panic_abort2.stderr b/src/tools/miri/tests/fail/panic/panic_abort2.stderr
index 7bb27e4baa0a5..e6a4380ea5187 100644
--- a/src/tools/miri/tests/fail/panic/panic_abort2.stderr
+++ b/src/tools/miri/tests/fail/panic/panic_abort2.stderr
@@ -1,6 +1,7 @@
 thread 'main' panicked at $DIR/panic_abort2.rs:LL:CC:
 42-panicking from libstd
 note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace
+note: in Miri, you may have to set `-Zmiri-env-forward=RUST_BACKTRACE` for the environment variable to have an effect
 error: abnormal termination: the program aborted execution
   --> RUSTLIB/panic_abort/src/lib.rs:LL:CC
    |
diff --git a/src/tools/miri/tests/fail/panic/panic_abort3.stderr b/src/tools/miri/tests/fail/panic/panic_abort3.stderr
index b46e8c2079580..23e2021eeef85 100644
--- a/src/tools/miri/tests/fail/panic/panic_abort3.stderr
+++ b/src/tools/miri/tests/fail/panic/panic_abort3.stderr
@@ -1,6 +1,7 @@
 thread 'main' panicked at $DIR/panic_abort3.rs:LL:CC:
 panicking from libcore
 note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace
+note: in Miri, you may have to set `-Zmiri-env-forward=RUST_BACKTRACE` for the environment variable to have an effect
 error: abnormal termination: the program aborted execution
   --> RUSTLIB/panic_abort/src/lib.rs:LL:CC
    |
diff --git a/src/tools/miri/tests/fail/panic/panic_abort4.stderr b/src/tools/miri/tests/fail/panic/panic_abort4.stderr
index b15f720e43f13..20a0ddb901926 100644
--- a/src/tools/miri/tests/fail/panic/panic_abort4.stderr
+++ b/src/tools/miri/tests/fail/panic/panic_abort4.stderr
@@ -1,6 +1,7 @@
 thread 'main' panicked at $DIR/panic_abort4.rs:LL:CC:
 42-panicking from libcore
 note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace
+note: in Miri, you may have to set `-Zmiri-env-forward=RUST_BACKTRACE` for the environment variable to have an effect
 error: abnormal termination: the program aborted execution
   --> RUSTLIB/panic_abort/src/lib.rs:LL:CC
    |
diff --git a/src/tools/miri/tests/fail/terminate-terminator.stderr b/src/tools/miri/tests/fail/terminate-terminator.stderr
index 8dbc802bf5955..f737adc561d9c 100644
--- a/src/tools/miri/tests/fail/terminate-terminator.stderr
+++ b/src/tools/miri/tests/fail/terminate-terminator.stderr
@@ -3,6 +3,7 @@ warning: You have explicitly enabled MIR optimizations, overriding Miri's defaul
 thread 'main' panicked at $DIR/terminate-terminator.rs:LL:CC:
 explicit panic
 note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace
+note: in Miri, you may have to set `-Zmiri-env-forward=RUST_BACKTRACE` for the environment variable to have an effect
 thread 'main' panicked at RUSTLIB/core/src/panicking.rs:LL:CC:
 panic in a function that cannot unwind
 stack backtrace:
diff --git a/src/tools/miri/tests/fail/unwind-action-terminate.stderr b/src/tools/miri/tests/fail/unwind-action-terminate.stderr
index 1323a3971003c..7e722f7be3288 100644
--- a/src/tools/miri/tests/fail/unwind-action-terminate.stderr
+++ b/src/tools/miri/tests/fail/unwind-action-terminate.stderr
@@ -1,6 +1,7 @@
 thread 'main' panicked at $DIR/unwind-action-terminate.rs:LL:CC:
 explicit panic
 note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace
+note: in Miri, you may have to set `-Zmiri-env-forward=RUST_BACKTRACE` for the environment variable to have an effect
 thread 'main' panicked at RUSTLIB/core/src/panicking.rs:LL:CC:
 panic in a function that cannot unwind
 stack backtrace:
diff --git a/src/tools/miri/tests/panic/div-by-zero-2.stderr b/src/tools/miri/tests/panic/div-by-zero-2.stderr
index 0f088ddd1a544..f0b84ea6fd606 100644
--- a/src/tools/miri/tests/panic/div-by-zero-2.stderr
+++ b/src/tools/miri/tests/panic/div-by-zero-2.stderr
@@ -1,3 +1,4 @@
 thread 'main' panicked at $DIR/div-by-zero-2.rs:LL:CC:
 attempt to divide by zero
 note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace
+note: in Miri, you may have to set `-Zmiri-env-forward=RUST_BACKTRACE` for the environment variable to have an effect
diff --git a/src/tools/miri/tests/panic/function_calls/exported_symbol_good_unwind.stderr b/src/tools/miri/tests/panic/function_calls/exported_symbol_good_unwind.stderr
index acc0e58885f23..f77f6f01119ec 100644
--- a/src/tools/miri/tests/panic/function_calls/exported_symbol_good_unwind.stderr
+++ b/src/tools/miri/tests/panic/function_calls/exported_symbol_good_unwind.stderr
@@ -1,6 +1,7 @@
 thread 'main' panicked at $DIR/exported_symbol_good_unwind.rs:LL:CC:
 explicit panic
 note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace
+note: in Miri, you may have to set `-Zmiri-env-forward=RUST_BACKTRACE` for the environment variable to have an effect
 thread 'main' panicked at $DIR/exported_symbol_good_unwind.rs:LL:CC:
 explicit panic
 thread 'main' panicked at $DIR/exported_symbol_good_unwind.rs:LL:CC:
diff --git a/src/tools/miri/tests/panic/oob_subslice.stderr b/src/tools/miri/tests/panic/oob_subslice.stderr
index 2bccb60352e0a..c116f8eb5250e 100644
--- a/src/tools/miri/tests/panic/oob_subslice.stderr
+++ b/src/tools/miri/tests/panic/oob_subslice.stderr
@@ -1,3 +1,4 @@
 thread 'main' panicked at $DIR/oob_subslice.rs:LL:CC:
 range end index 5 out of range for slice of length 4
 note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace
+note: in Miri, you may have to set `-Zmiri-env-forward=RUST_BACKTRACE` for the environment variable to have an effect
diff --git a/src/tools/miri/tests/panic/overflowing-lsh-neg.stderr b/src/tools/miri/tests/panic/overflowing-lsh-neg.stderr
index 2cff81c58af10..1d057ea5eb4ba 100644
--- a/src/tools/miri/tests/panic/overflowing-lsh-neg.stderr
+++ b/src/tools/miri/tests/panic/overflowing-lsh-neg.stderr
@@ -1,3 +1,4 @@
 thread 'main' panicked at $DIR/overflowing-lsh-neg.rs:LL:CC:
 attempt to shift left with overflow
 note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace
+note: in Miri, you may have to set `-Zmiri-env-forward=RUST_BACKTRACE` for the environment variable to have an effect
diff --git a/src/tools/miri/tests/panic/overflowing-rsh-1.stderr b/src/tools/miri/tests/panic/overflowing-rsh-1.stderr
index 13117df5fc39a..d1a79400bfabe 100644
--- a/src/tools/miri/tests/panic/overflowing-rsh-1.stderr
+++ b/src/tools/miri/tests/panic/overflowing-rsh-1.stderr
@@ -1,3 +1,4 @@
 thread 'main' panicked at $DIR/overflowing-rsh-1.rs:LL:CC:
 attempt to shift right with overflow
 note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace
+note: in Miri, you may have to set `-Zmiri-env-forward=RUST_BACKTRACE` for the environment variable to have an effect
diff --git a/src/tools/miri/tests/panic/overflowing-rsh-2.stderr b/src/tools/miri/tests/panic/overflowing-rsh-2.stderr
index 986a66f899188..612b0c0c4c21f 100644
--- a/src/tools/miri/tests/panic/overflowing-rsh-2.stderr
+++ b/src/tools/miri/tests/panic/overflowing-rsh-2.stderr
@@ -1,3 +1,4 @@
 thread 'main' panicked at $DIR/overflowing-rsh-2.rs:LL:CC:
 attempt to shift right with overflow
 note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace
+note: in Miri, you may have to set `-Zmiri-env-forward=RUST_BACKTRACE` for the environment variable to have an effect
diff --git a/src/tools/miri/tests/panic/panic2.stderr b/src/tools/miri/tests/panic/panic2.stderr
index bee1af2bef662..792c71346fd6a 100644
--- a/src/tools/miri/tests/panic/panic2.stderr
+++ b/src/tools/miri/tests/panic/panic2.stderr
@@ -1,3 +1,4 @@
 thread 'main' panicked at $DIR/panic2.rs:LL:CC:
 42-panicking from libstd
 note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace
+note: in Miri, you may have to set `-Zmiri-env-forward=RUST_BACKTRACE` for the environment variable to have an effect
diff --git a/src/tools/miri/tests/panic/panic3.stderr b/src/tools/miri/tests/panic/panic3.stderr
index 8dac000d291bc..f8016bc3912d2 100644
--- a/src/tools/miri/tests/panic/panic3.stderr
+++ b/src/tools/miri/tests/panic/panic3.stderr
@@ -1,3 +1,4 @@
 thread 'main' panicked at $DIR/panic3.rs:LL:CC:
 panicking from libcore
 note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace
+note: in Miri, you may have to set `-Zmiri-env-forward=RUST_BACKTRACE` for the environment variable to have an effect
diff --git a/src/tools/miri/tests/panic/panic4.stderr b/src/tools/miri/tests/panic/panic4.stderr
index 13437fe7f0751..67410bf3b1a0e 100644
--- a/src/tools/miri/tests/panic/panic4.stderr
+++ b/src/tools/miri/tests/panic/panic4.stderr
@@ -1,3 +1,4 @@
 thread 'main' panicked at $DIR/panic4.rs:LL:CC:
 42-panicking from libcore
 note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace
+note: in Miri, you may have to set `-Zmiri-env-forward=RUST_BACKTRACE` for the environment variable to have an effect
diff --git a/src/tools/miri/tests/panic/transmute_fat2.stderr b/src/tools/miri/tests/panic/transmute_fat2.stderr
index 1f09a2c1a082c..2ee01d469312b 100644
--- a/src/tools/miri/tests/panic/transmute_fat2.stderr
+++ b/src/tools/miri/tests/panic/transmute_fat2.stderr
@@ -1,3 +1,4 @@
 thread 'main' panicked at $DIR/transmute_fat2.rs:LL:CC:
 index out of bounds: the len is 0 but the index is 0
 note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace
+note: in Miri, you may have to set `-Zmiri-env-forward=RUST_BACKTRACE` for the environment variable to have an effect
diff --git a/src/tools/miri/tests/panic/unsupported_foreign_function.stderr b/src/tools/miri/tests/panic/unsupported_foreign_function.stderr
index 4db1e2909618a..d0a7d8dafc5a4 100644
--- a/src/tools/miri/tests/panic/unsupported_foreign_function.stderr
+++ b/src/tools/miri/tests/panic/unsupported_foreign_function.stderr
@@ -1,3 +1,4 @@
 thread 'main' panicked at $DIR/unsupported_foreign_function.rs:LL:CC:
 unsupported Miri functionality: can't call foreign function `foo` on $OS
 note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace
+note: in Miri, you may have to set `-Zmiri-env-forward=RUST_BACKTRACE` for the environment variable to have an effect
diff --git a/src/tools/miri/tests/panic/unsupported_syscall.stderr b/src/tools/miri/tests/panic/unsupported_syscall.stderr
index 40ba6671d5b6d..f802159cb1cf8 100644
--- a/src/tools/miri/tests/panic/unsupported_syscall.stderr
+++ b/src/tools/miri/tests/panic/unsupported_syscall.stderr
@@ -1,3 +1,4 @@
 thread 'main' panicked at $DIR/unsupported_syscall.rs:LL:CC:
 unsupported Miri functionality: can't execute syscall with ID 0
 note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace
+note: in Miri, you may have to set `-Zmiri-env-forward=RUST_BACKTRACE` for the environment variable to have an effect
diff --git a/src/tools/miri/tests/pass/panic/catch_panic.stderr b/src/tools/miri/tests/pass/panic/catch_panic.stderr
index cbcd626e39fb4..a472a5d80cb76 100644
--- a/src/tools/miri/tests/pass/panic/catch_panic.stderr
+++ b/src/tools/miri/tests/pass/panic/catch_panic.stderr
@@ -1,6 +1,7 @@
 thread 'main' panicked at $DIR/catch_panic.rs:LL:CC:
 Hello from std::panic
 note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace
+note: in Miri, you may have to set `-Zmiri-env-forward=RUST_BACKTRACE` for the environment variable to have an effect
 Caught panic message (&str): Hello from std::panic
 thread 'main' panicked at $DIR/catch_panic.rs:LL:CC:
 Hello from std::panic: 1
diff --git a/src/tools/miri/tests/pass/panic/concurrent-panic.stderr b/src/tools/miri/tests/pass/panic/concurrent-panic.stderr
index 0bb3dcd8d248c..b2a5cf4922c88 100644
--- a/src/tools/miri/tests/pass/panic/concurrent-panic.stderr
+++ b/src/tools/miri/tests/pass/panic/concurrent-panic.stderr
@@ -3,6 +3,7 @@ Thread 1 reported it has started
 thread '<unnamed>' panicked at $DIR/concurrent-panic.rs:LL:CC:
 panic in thread 2
 note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace
+note: in Miri, you may have to set `-Zmiri-env-forward=RUST_BACKTRACE` for the environment variable to have an effect
 Thread 2 blocking on thread 1
 Thread 2 reported it has started
 Unlocking mutex
diff --git a/src/tools/miri/tests/pass/panic/nested_panic_caught.stderr b/src/tools/miri/tests/pass/panic/nested_panic_caught.stderr
index 4684beb33383a..3efb4be40f911 100644
--- a/src/tools/miri/tests/pass/panic/nested_panic_caught.stderr
+++ b/src/tools/miri/tests/pass/panic/nested_panic_caught.stderr
@@ -1,6 +1,7 @@
 thread 'main' panicked at $DIR/nested_panic_caught.rs:LL:CC:
 once
 note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace
+note: in Miri, you may have to set `-Zmiri-env-forward=RUST_BACKTRACE` for the environment variable to have an effect
 thread 'main' panicked at $DIR/nested_panic_caught.rs:LL:CC:
 twice
 stack backtrace:
diff --git a/src/tools/miri/tests/pass/panic/thread_panic.stderr b/src/tools/miri/tests/pass/panic/thread_panic.stderr
index badd409d13fab..bdfe4f98ba369 100644
--- a/src/tools/miri/tests/pass/panic/thread_panic.stderr
+++ b/src/tools/miri/tests/pass/panic/thread_panic.stderr
@@ -1,5 +1,6 @@
 thread '<unnamed>' panicked at $DIR/thread_panic.rs:LL:CC:
 Hello!
 note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace
+note: in Miri, you may have to set `-Zmiri-env-forward=RUST_BACKTRACE` for the environment variable to have an effect
 thread 'childthread' panicked at $DIR/thread_panic.rs:LL:CC:
 Hello, world!