Adding upstream version 1.64.0+dfsg1.upstream/1.64.0+dfsg1

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

4 files changed, 67 insertions, 0 deletions

diff --git a/src/doc/book/listings/ch15-smart-pointers/listing-15-26/Cargo.lock b/src/doc/book/listings/ch15-smart-pointers/listing-15-26/Cargo.lock
new file mode 100644
index 000000000..a792c49aa
--- /dev/null
+++ b/src/doc/book/listings/ch15-smart-pointers/listing-15-26/Cargo.lock
@@ -0,0 +1,6 @@
+# This file is automatically @generated by Cargo.
+# It is not intended for manual editing.
+[[package]]
+name = "cons-list"
+version = "0.1.0"
+
diff --git a/src/doc/book/listings/ch15-smart-pointers/listing-15-26/Cargo.toml b/src/doc/book/listings/ch15-smart-pointers/listing-15-26/Cargo.toml
new file mode 100644
index 000000000..dce1515c3
--- /dev/null
+++ b/src/doc/book/listings/ch15-smart-pointers/listing-15-26/Cargo.toml
@@ -0,0 +1,6 @@
+[package]
+name = "cons-list"
+version = "0.1.0"
+edition = "2021"
+
+[dependencies]
diff --git a/src/doc/book/listings/ch15-smart-pointers/listing-15-26/output.txt b/src/doc/book/listings/ch15-smart-pointers/listing-15-26/output.txt
new file mode 100644
index 000000000..8b8eb40b6
--- /dev/null
+++ b/src/doc/book/listings/ch15-smart-pointers/listing-15-26/output.txt
@@ -0,0 +1,11 @@
+$ cargo run
+   Compiling cons-list v0.1.0 (file:///projects/cons-list)
+    Finished dev [unoptimized + debuginfo] target(s) in 0.53s
+     Running `target/debug/cons-list`
+a initial rc count = 1
+a next item = Some(RefCell { value: Nil })
+a rc count after b creation = 2
+b initial rc count = 1
+b next item = Some(RefCell { value: Cons(5, RefCell { value: Nil }) })
+b rc count after changing a = 2
+a rc count after changing a = 2
diff --git a/src/doc/book/listings/ch15-smart-pointers/listing-15-26/src/main.rs b/src/doc/book/listings/ch15-smart-pointers/listing-15-26/src/main.rs
new file mode 100644
index 000000000..08963aaa5
--- /dev/null
+++ b/src/doc/book/listings/ch15-smart-pointers/listing-15-26/src/main.rs
@@ -0,0 +1,44 @@
+use crate::List::{Cons, Nil};
+use std::cell::RefCell;
+use std::rc::Rc;
+
+#[derive(Debug)]
+enum List {
+    Cons(i32, RefCell<Rc<List>>),
+    Nil,
+}
+
+impl List {
+    fn tail(&self) -> Option<&RefCell<Rc<List>>> {
+        match self {
+            Cons(_, item) => Some(item),
+            Nil => None,
+        }
+    }
+}
+
+// ANCHOR: here
+fn main() {
+    let a = Rc::new(Cons(5, RefCell::new(Rc::new(Nil))));
+
+    println!("a initial rc count = {}", Rc::strong_count(&a));
+    println!("a next item = {:?}", a.tail());
+
+    let b = Rc::new(Cons(10, RefCell::new(Rc::clone(&a))));
+
+    println!("a rc count after b creation = {}", Rc::strong_count(&a));
+    println!("b initial rc count = {}", Rc::strong_count(&b));
+    println!("b next item = {:?}", b.tail());
+
+    if let Some(link) = a.tail() {
+        *link.borrow_mut() = Rc::clone(&b);
+    }
+
+    println!("b rc count after changing a = {}", Rc::strong_count(&b));
+    println!("a rc count after changing a = {}", Rc::strong_count(&a));
+
+    // Uncomment the next line to see that we have a cycle;
+    // it will overflow the stack
+    // println!("a next item = {:?}", a.tail());
+}
+// ANCHOR_END: here