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# Summary Reference

> Quick understanding of Assemby Memory Pointers which indicate which rust data structures are on the *stack* or *heap*

## Summary Differences of Stack and Heap (Rust)

## 📌 Stack vs Heap in Assembly (Rust)

| Feature | Stack 🟢 | Heap 🔴 |
|---------------|---------|--------|
| **Storage Type** | Fixed-size, local variables | Dynamic memory allocation |
| **Memory Access** | `[rsp + offset]` (direct access) | `mov rax, [ptr]` (pointer dereference) |
| **Allocation** | `sub rsp, X` (manual) | `call __rust_alloc` (dynamic) |
| **Deallocation** | `add rsp, X` (automatic on function return) | `call __rust_dealloc` (manual via `drop`) |
| **Ownership** | Function scope (auto cleanup) | Must be explicitly freed (`Box`, `Rc`, etc.) |
| **Lifetime** | Short (until function exits) | Long (until manually freed) |
| **Speed** | Faster (LIFO, cache-friendly) | Slower (fragmentation, extra pointer indirection) |
| **Common Uses** | Local variables, function calls | `Vec<T>`, `Box<T>`, `Rc<T>`, `Arc<T>` |
| **Example Allocation** | `sub rsp, 32` (reserve 32 bytes) | `call __rust_alloc` (allocate heap memory) |
| **Example Access** | `mov rax, [rsp + 16]` (stack var) | `mov rax, [rax]` (dereferencing heap ptr) |

## 📌 Stack vs Heap Pointers in Assembly (Rust)

| Rust Pointer Type | Stack or Heap? | Assembly Pattern |
|--------------------|---------------|------------------|
| **`&T` (Reference)** | **Stack** ✅ | `lea rdi, [rsp + offset]` (passing address of stack var) |
| **`&mut T` (Mutable Reference)** | **Stack** ✅ | `mov rax, [rsp + offset]` (reading/modifying stack var) |
| **`Box<T>`** | **Heap** ✅ | `call __rust_alloc` (allocates memory) → `mov [rsp + offset], rax` (stores heap pointer on stack) |
| **`Rc<T>`** | **Heap** ✅ | `call __rust_alloc` + `lock inc qword ptr [rax]` (reference counting) |
| **`Arc<T>`** | **Heap** ✅ | `call __rust_alloc` + `lock inc qword ptr [rax]` (atomic reference counting) |
| **`Vec<T>`** | **Heap** ✅ | `call __rust_alloc` (allocates memory) + `mov [rsp + offset], rax` (stores heap pointer) |
| **`String`** | **Heap** ✅ | `call __rust_alloc` (allocates memory) + `mov rax, [ptr]` (accessing string) |
| **`&str` (String Slice)** | **Stack** ✅ (if `&"hello"`) / **Heap** ✅ (if from `String`) | `lea rax, [rip + .L__unnamed]` (stack) OR `mov rax, [ptr]` (heap) |
| **`*const T` / `*mut T` (Raw Pointer)** | **Stack** (points to stack) or **Heap** (points to heap) | `mov rax, [rsp + offset]` (stack) OR `mov rax, [ptr]` (heap) |