stackheap notes

src/memory-management/manual.md

@@ -2,6 +2,8 @@
 
 You allocate and deallocate heap memory yourself.
 
+If not done with care, this can lead to crashes, bugs, security vulnerabilities, and memory leaks.
+
 ## C Example
 
 You must call `free` on every pointer you allocate with `malloc`:

src/memory-management/rust.md

@@ -3,7 +3,22 @@
 Memory management in Rust is a mix:
 
 * Safe and correct like Java, but without a garbage collector.
+* Depending on which abstraction (or combonation of abstractions) you choose, can be a single unique pointer, reference counted, or atomically reference counted.
 * Scope-based like C++, but the compiler enforces full adherence.
-* Has no runtime overhead like in C and C++.
+* A rust user can choose the right abstraction for the situation, some even have no cost at runtime like C.
 
 It achieves this by modeling _ownership_ explicitly.
+
+<details>
+
+* If asked how at this point, you can mention that in rust this is usually handled by RAII wrapper types such as [Box], [Vec], [Rc], or [Arc]. These encapsulate ownership and memory allocation via various means, and prevent the potential errors in C.
+
+* You may be asked about destructors here, the [Drop] trait is the rust equivalent.
+
+</details>
+
+[Box]: https://doc.rust-lang.org/std/boxed/struct.Box.html
+[Vec]: https://doc.rust-lang.org/std/vec/struct.Vec.html
+[Rc]: https://doc.rust-lang.org/std/rc/struct.Rc.html
+[Arc]: https://doc.rust-lang.org/std/sync/struct.Arc.html
+[Drop]: https://doc.rust-lang.org/std/ops/trait.Drop.html

src/memory-management/stack.md

@@ -22,3 +22,14 @@ fn main() {
 :                           :     `- - - - - - - - - - - - - - - -'
 `- - - - - - - - - - - - - -'
 ```
+
+<details>
+
+* Mention that a `String` is backed by a `Vec`, so it has a capacity and length and can grow if mutable via reallocation on the heap.
+
+* If students ask about it, you can mention that the underlying memory is heap allocated using the [System Allocator] and custom allocators can be implemented using the [Allocator Api]
+
+</details>
+
+[System Allocator]: https://doc.rust-lang.org/std/alloc/struct.System.html
+[Allocator Api]: https://doc.rust-lang.org/std/alloc/index.html