Zig Allocator interface signature changes between 0.11.0 and nightly

Breaking changes in the Allocator API

Based on the evolution of the nightly branch, the following signatures in std.mem.Allocator differ from those in Zig 0.11.0:

1. Heap allocation methods (alloc, allocSlice, memAlloc, resize) now return an explicit error union:

![]u8  →  error{OutOfMemory}![]u8
![]T   →  error{OutOfMemory}![]T

2. Typed allocation (create) changed from returning a raw pointer to returning the same error set:

*T   →  error{OutOfMemory}! *T

3. GeneralPurposeAllocator initialization now returns a struct that must be de‑initialized:

.init(parent) → GPA
.deinit()   // required to free internal bookkeeping

4. Owned slice helper – the old ownedSlice helper was removed; nightly provides Allocator.ownedSlice with a matching signature.
5. Vtable visibility – the _vtable field is now private; direct access no longer compiles.

Recommended forward‑compatible error‑handling pattern

To stay compatible with both 0.11.0‑style code and the upcoming stabilized API, use the following approach:

• Always treat allocation results as potentially failing with error.OutOfMemory.
• Use try/catch or value‑error unwrapping:

const ptr = try allocator.alloc(u8, size);
// or
const ptr = allocator.alloc(u8, size) catch |err| {
    switch (err) {
        error.OutOfMemory => { /* handle OOM */ }
        else => return err,
    }
};
// remember to free when done
allocator.free(ptr);

• For typed allocation with create:

const obj = try allocator.create(MyStruct);
// or handle the error similarly
const obj = allocator.create(MyStruct) catch |err| {
    switch (err) { error.OutOfMemory => /* … */ else => return err };
};
// de‑init when finished
allocator.destroy(obj);

• When using GeneralPurposeAllocator, always pair .init with a matching .deinit in the same scope or via defer:

const gpa = std.heap.GeneralPurposeAllocator(.{}).init(parent_allocator) catch return error;
defer gpa.deinit();
const allocator = gpa.allocator();

Verification steps (optional)

If you want to confirm the current signatures on your nightly toolchain:

1. Clone the Zig repository and checkout the nightly branch:

git clone https://github.com/ziglang/zig
cd zig
git checkout master

2. Inspect the allocator definition:

cat std/mem.allocator.zig | grep -A2 'pub fn alloc'

3. Compile a minimal test program that calls alloc, create, and GeneralPurposeAllocator.init/deinit and ensure the compiler expects the error{OutOfMemory} union and flags a missing .deinit as an error.

Note: the nightly API may still evolve before the next stable release; keep an eye on the release notes for any further adjustments.