From ac66baad1a9787f60ff86fac125da8176e053dbc Mon Sep 17 00:00:00 2001
From: Ralf Jung <post@ralfj.de>
Date: Wed, 3 Aug 2022 22:48:12 -0400
Subject: [PATCH] add miri-test-libstd support to libstd

---
 library/alloc/src/lib.rs | 1 +
 library/std/src/lib.rs   | 8 ++++++++
 2 files changed, 9 insertions(+)

diff --git a/library/alloc/src/lib.rs b/library/alloc/src/lib.rs
index 8b6f4054851..a6f3593addc 100644
--- a/library/alloc/src/lib.rs
+++ b/library/alloc/src/lib.rs
@@ -60,6 +60,7 @@
 // able to "empty" this crate. See <https://github.com/rust-lang/miri-test-libstd/issues/4>.
 // rustc itself never sets the feature, so this line has no affect there.
 #![cfg(any(not(feature = "miri-test-libstd"), test, doctest))]
+//
 #![allow(unused_attributes)]
 #![stable(feature = "alloc", since = "1.36.0")]
 #![doc(
diff --git a/library/std/src/lib.rs b/library/std/src/lib.rs
index a8d6645794a..bbd7041c50b 100644
--- a/library/std/src/lib.rs
+++ b/library/std/src/lib.rs
@@ -187,6 +187,14 @@
 //! [rust-discord]: https://discord.gg/rust-lang
 //! [array]: prim@array
 //! [slice]: prim@slice
+
+// To run libstd tests without x.py without ending up with two copies of libstd, Miri needs to be
+// able to "empty" this crate. See <https://github.com/rust-lang/miri-test-libstd/issues/4>.
+// rustc itself never sets the feature, so this line has no affect there.
+#![cfg(any(not(feature = "miri-test-libstd"), test, doctest))]
+// miri-test-libstd also prefers to make std use the sysroot versions of the dependencies.
+#![cfg_attr(feature = "miri-test-libstd", feature(rustc_private))]
+//
 #![cfg_attr(not(feature = "restricted-std"), stable(feature = "rust1", since = "1.0.0"))]
 #![cfg_attr(feature = "restricted-std", unstable(feature = "restricted_std", issue = "none"))]
 #![doc(