fix(bindings): refcount Pool to fix teardown panic

[GrapeBaBa]

Motivation

Reproduces on main and every binding-feature branch (#165, #346, #351): any process that holds a BeaconStateView at module scope panics during process exit:

thread N panic: incorrect alignment
src/persistent_merkle_tree/Node.zig:387:9 in unref
src/ssz/tree_view/chunks.zig:38:30 in deinit
src/ssz/tree_view/container.zig:97:49 in clearChildrenDataCache
src/state_transition/cache/state_cache.zig:102:26 in deinit

Process exits with code 134 (SIGABRT) instead of 0.

Root cause: NAPI env cleanup hook (napi_add_env_cleanup_hook) fires before module-level JS holders of native objects are finalized. The previous cleanup callback unconditionally called pool.state.deinit(), freeing the Node.Pool's MultiArrayList storage. Live BeaconStateView instances rooted by module-level const had not yet been finalized; when their finalizers eventually ran, the chained pool.unref(self.root) walked freed memory and panicked.

Module-scope is the standard pattern for benchmark fixtures (@chainsafe/benchmark + perf tests). Without the fix, every such test exits non-zero even when the bench itself succeeds.

Description

Wrap Node.Pool in the existing RefCount(T) (src/state_transition/utils/ref_count.zig):

• Module init holds ref = 1.
• Each BeaconStateView that owns a cached_state holds another ref.
• pool.state.deinit() releases the module ref but only actually destroys the pool when the count reaches zero — deferring destruction past every live view's finalizer.

Order in BeaconStateView.deinit:

1. cached_state.deinit() — does all the pool.unref(...) calls
2. pool_rc.unref() — releases this view's pool ref; if last, real pool.deinit runs here

[gemini-code-assist]

Summary of Changes

Hello, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request addresses a critical teardown panic occurring in native bindings when BeaconStateView instances are held at the module scope. By implementing a reference counting wrapper for the Node.Pool, the system now correctly defers pool destruction until all active views have been finalized, ensuring memory safety during NAPI environment cleanup.

Highlights

• Reference Counting for Node.Pool: Introduced a reference counting mechanism for the Node.Pool to ensure it remains alive until all dependent BeaconStateView instances are finalized, preventing premature memory deallocation.
• NAPI Teardown Fix: Updated the NAPI environment cleanup hook to release the module's reference to the pool rather than unconditionally destroying it, resolving SIGABRT panics during process exit.
• Regression Testing: Added a new integration test that verifies module-scope BeaconStateView instances do not cause panics during process teardown.

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[gemini-code-assist]

Code Review

This pull request introduces reference counting for the shared Node.Pool used by BeaconStateView to prevent 'incorrect alignment' panics during NAPI environment cleanup at process exit. The pool.zig module now wraps the pool in a RefCount structure, and BeaconStateView instances hold a strong reference to this pool for their lifetime. A new teardown test ensures that module-scope views exit cleanly. Feedback focuses on adhering to the repository's style guide regarding proper acronym capitalization (e.g., renaming PoolRc to PoolRC) and increasing assertion density to verify that the pool is initialized before access.

[gemini-code-assist]

According to the style guide (Rule 224), acronyms should use proper capitalization. Since RC stands for Reference Count, it should be capitalized as PoolRC.

pub const PoolRC = RefCount(Node.Pool);

References

1. Use proper capitalization for acronyms (VSRState, not VsrState). ^(link)

[gemini-code-assist]

Update the type name to PoolRC to adhere to the acronym capitalization rule.

    pool_rc: ?*PoolRC = null,

[gemini-code-assist]

Update the type name to PoolRC to adhere to the acronym capitalization rule.

        self.pool_rc = try PoolRC.init(allocator, pool_value);

[gemini-code-assist]

The style guide (Rule 51) requires asserting function arguments and invariants. Adding an explicit assertion here improves safety and follows the 'fail-fast' principle.

    pub fn pool(self: *State) *Node.Pool {
        std.debug.assert(self.pool_rc != null);
        return &self.pool_rc.?.instance;
    }

References

1. Assert all function arguments and return values, pre/postconditions and invariants. ^(link)

[gemini-code-assist]

Rename the function to poolRC and update the return type to PoolRC to adhere to the acronym capitalization rule (Rule 224). Additionally, add an assertion for the pool initialization invariant.

    pub fn poolRC(self: *State) *PoolRC {
        std.debug.assert(self.pool_rc != null);
        return self.pool_rc.?;
    }

[gemini-code-assist]

Update the type reference to PoolRC to match the updated naming convention in pool.zig.

pool_rc: ?*pool.PoolRC = null,

[gemini-code-assist]

Add an assertion to verify that the shared pool is initialized before use, as required by the style guide's assertion density and safety rules (Rule 51).

    std.debug.assert(pool.state.pool_rc != null);
    state.* = try AnyBeaconState.deserialize(allocator, pool.state.pool(), fork_seq, byte_slice);

[gemini-code-assist]

Update the call to poolRC() to match the renamed function in pool.zig.

        .pool_rc = pool.state.poolRC().ref(),

[gemini-code-assist]

Add an assertion to verify that the shared pool is initialized before returning a new view, ensuring the invariant holds and increasing assertion density.

    std.debug.assert(pool.state.pool_rc != null);
    return .{

[gemini-code-assist]

Update the call to poolRC() to match the renamed function in pool.zig.

        .pool_rc = pool.state.poolRC().ref(),