How to allocate structs on the heap without taking up space on the stack in stable Rust?

Question

In this code...

struct Test { a: i32, b: i64 }
    
fn foo() -> Box {              // Stack frame:
            


        

Answer 1

You seem to be looking for the box_syntax feature, however as of Rust 1.39.0 it is not stable and only available with a nightly compiler. It also seems like this feature will not be stabilized any time soon, and might have a different design if it ever gets stabilized.

On a nightly compiler, you can write:

#![feature(box_syntax)]

struct Test { a: i32, b: i64 }

fn foo() -> Box {
    box Test { a: 123, b: 456 }
}