Crate heap_arr 

Allocate fixed-size arrays directly on the heap.

The Problem

In Rust, Box::new([T; N]) allocates on the stack first, then moves to the heap. For large arrays, this can overflow the stack. Rust’s optimizer should handle this in optimized builds, but not in debug.

The Solution

This crate allocates [T; N] directly on the heap, skipping the intermediate stack allocation.

Example

const SIZE: usize = 1_000_000_000;
// This would overflow the stack in debug mode:
// let arr = Box::new([0u8; SIZE]);

// This works everywhere:
let arr: Box<[u8; SIZE]> = heap_arr::new_copied(&0u8);
assert_eq!(arr[0], 0);

API

• new_copied – Allocate and fill by copying a value (for T: Copy)
• new_cloned – Allocate and fill by cloning a value (for T: Clone)
• new_default – Allocate and fill with T::default()
• from_fn – Initialize via a closure
• try_from_fn – Initialize with a fallible closure
• uninit – Allocate uninitialized memory
• assume_init – Transmute uninitialized memory (unsafe)

All functions return Box<[T; N]> compatible with standard library code.

Features

• #![no_std] compatible (uses alloc only)
• Panic-safe initialization with automatic cleanup on drop
• Zero unsafe surface area for new_* functions

Functions

assume_init^⚠

A helper function to transmute Box<[MaybeUninit<T>; N]> into Box<[T; N]>.

from_fn

Allocates [T; N] directly on the heap and initializes its entries to values produced by calling f with the index of the entry as argument while walking forward through the array.

new_cloned

Allocates [T; N] directly on the heap and initializes its entries to initial by cloning it. For T that are not Clone, see new_copied.

new_copied

Allocates [T; N] directly on the heap and initializes its entries to initial by copying it. For T that are not Copy, see new_cloned.

new_default

Allocates [T; N] directly on the heap and initializes its entries to T::default().

try_from_fn

Allocates [T; N] directly on the heap and initializes its entries to values produced by calling f with the index of the entry as argument while walking forward through the array.

uninit

Allocates [T; N] directly on the heap and leaves its entries uninitialized.