# Memory (env)

> NeuroWASM memory host functions — allocate, deallocate and abort — and the memory layout rules a contract must follow.

Source: https://docs.nro.world/neurowasm/memory

The contract exports one linear `memory`. Host functions read and write it through `(ptr, len)` pairs; a pointer or length outside the memory makes the host function fail (usually returning `-1`) rather than trap.

The VM copies the call input to **offset 64**; see [Guest exports → call](./exports#call).

## `allocate` <Badge type="tip" text="live" />

```text
(import "env" "allocate" (func (param i32) (result i32)))
allocate(size: i32) → ptr: i32
```

Reserves `size` bytes with a bump allocator and returns the start. The host only advances a cursor — it does not grow the memory, so the contract must make sure the range exists. Negative sizes count as 0; a single request is capped at **1 MiB**. For toolchains (AssemblyScript and similar) that expect the host to allocate.

## `deallocate` <Badge type="tip" text="live" />

```text
(import "env" "deallocate" (func (param i32)))
```

Does nothing — the bump allocator never frees. Present so code written for allocator interfaces links.

## `abort` <Badge type="tip" text="live" />

```text
(import "env" "abort" (func (param i32 i32 i32 i32)))
```

The AssemblyScript abort hook, accepted so such modules link. **It does nothing and does not stop execution** — AssemblyScript follows it with `unreachable`, which is what fails the call. To fail a call deliberately, trap (`unreachable`), which rolls back the whole call tree, or return an error with `set_return` when the caller should see a message.