From 0b3ebb546fac5de6be624d335abb3c5f7ad82c74 Mon Sep 17 00:00:00 2001
From: Zachary S <zasample18+github@gmail.com>
Date: Sat, 11 May 2024 07:11:36 -0500
Subject: [PATCH] Add note about possible allocation-sharing to
 Arc/Rc<str/[T]/CStr>::default.

---
 library/alloc/src/ffi/c_str.rs | 4 ++++
 library/alloc/src/rc.rs        | 4 ++++
 library/alloc/src/sync.rs      | 4 ++++
 3 files changed, 12 insertions(+)

diff --git a/library/alloc/src/ffi/c_str.rs b/library/alloc/src/ffi/c_str.rs
index 19dd90eb81f..3b56a5717e2 100644
--- a/library/alloc/src/ffi/c_str.rs
+++ b/library/alloc/src/ffi/c_str.rs
@@ -914,6 +914,8 @@ impl From<&CStr> for Rc<CStr> {
 #[stable(feature = "more_rc_default_impls", since = "CURRENT_RUSTC_VERSION")]
 impl Default for Arc<CStr> {
     /// Creates an empty CStr inside an Arc
+    ///
+    /// This may or may not share an allocation with other Arcs.
     #[inline]
     fn default() -> Self {
         let c_str: &CStr = Default::default();
@@ -925,6 +927,8 @@ impl Default for Arc<CStr> {
 #[stable(feature = "more_rc_default_impls", since = "CURRENT_RUSTC_VERSION")]
 impl Default for Rc<CStr> {
     /// Creates an empty CStr inside an Rc
+    ///
+    /// This may or may not share an allocation with other Rcs on the same thread.
     #[inline]
     fn default() -> Self {
         let c_str: &CStr = Default::default();
diff --git a/library/alloc/src/rc.rs b/library/alloc/src/rc.rs
index 206489876e3..dddd0603a15 100644
--- a/library/alloc/src/rc.rs
+++ b/library/alloc/src/rc.rs
@@ -2228,6 +2228,8 @@ impl<T: Default> Default for Rc<T> {
 #[stable(feature = "more_rc_default_impls", since = "CURRENT_RUSTC_VERSION")]
 impl Default for Rc<str> {
     /// Creates an empty str inside an Rc
+    ///
+    /// This may or may not share an allocation with other Rcs on the same thread.
     #[inline]
     fn default() -> Self {
         Rc::from("")
@@ -2238,6 +2240,8 @@ impl Default for Rc<str> {
 #[stable(feature = "more_rc_default_impls", since = "CURRENT_RUSTC_VERSION")]
 impl<T> Default for Rc<[T]> {
     /// Creates an empty `[T]` inside an Rc
+    ///
+    /// This may or may not share an allocation with other Rcs on the same thread.
     #[inline]
     fn default() -> Self {
         let arr: [T; 0] = [];
diff --git a/library/alloc/src/sync.rs b/library/alloc/src/sync.rs
index 5f6ce80e194..f06994f7c40 100644
--- a/library/alloc/src/sync.rs
+++ b/library/alloc/src/sync.rs
@@ -3304,6 +3304,8 @@ impl<T: Default> Default for Arc<T> {
 #[stable(feature = "more_rc_default_impls", since = "CURRENT_RUSTC_VERSION")]
 impl Default for Arc<str> {
     /// Creates an empty str inside an Arc
+    ///
+    /// This may or may not share an allocation with other Arcs.
     #[inline]
     fn default() -> Self {
         Arc::from("")
@@ -3314,6 +3316,8 @@ impl Default for Arc<str> {
 #[stable(feature = "more_rc_default_impls", since = "CURRENT_RUSTC_VERSION")]
 impl<T> Default for Arc<[T]> {
     /// Creates an empty `[T]` inside an Arc
+    ///
+    /// This may or may not share an allocation with other Arcs.
     #[inline]
     fn default() -> Self {
         let arr: [T; 0] = [];