Q007. Is ownership related to whether a value is stored on the stack or the heap?

Short Answer

No. Ownership describes lifecycle and cleanup responsibility, while stack and heap describe storage. An i32 may live entirely in a register or stack slot, an array may be inline on the stack, and a String typically has a small owning handle in local storage with its bytes on the heap. All of them participate in ownership.

Deep Dive

Storage location depends on representation and compiler optimization:

• fixed-size local values can be stored inline in a stack frame or registers;
• String, Vec<T>, and Box<T> manage heap allocations through owning pointers;
• a struct owns inline fields regardless of whether the struct itself is on the stack or heap;
• a File value can store a small handle to a resource managed by the OS kernel.

Moving a heap-owning value normally transfers its handle. The allocation does not move. Moving a large inline value may require copying its bytes, although the optimizer can reuse storage or eliminate the copy.

Internal Model

A stack frame contains storage needed by an active function call. Heap allocations are obtained through an allocator and have independent addresses and lifetimes. CPU registers may hold values that source code describes as local variables.

Ownership analysis happens before final storage placement. The generated machine code contains data movement and cleanup operations, not a stack-versus-heap ownership flag.

Example

fn main() {
    let inline = [0_u8; 16];
    let dynamic = vec![0_u8; 16];
    let moved = dynamic;

    println!("{} {}", inline.len(), moved.len());
}

Common Mistakes

• Saying the stack stores only pointers to heap values.
• Assuming every local variable has a physical stack slot.
• Thinking a move relocates the underlying heap allocation.

Follow-ups

• What is stored inline for String, Vec<T>, and Box<T>?
• What happens when a stack frame exceeds its available stack space?
• Can moving a large inline value have a runtime cost?

Related

• Q005. What does it mean for a value to own a resource?
• Q006. What is the difference between an owner, a binding, a value, and a resource?
• Q009. Does Rust ownership have a runtime cost?

References

• The Rust Programming Language
• Rust Reference
• Rust Standard Library