Attempt to spawn an object at pool record with payload!…

Error message

Attempt to spawn an object at pool record with payload! Record index is {free_index}

What it means

Pool::spawn_with reuses a record popped from the free stack and asserts the record is truly empty (no payload). Finding a payload there means the free-list and record states are out of sync — an internal invariant violation indicating pool corruption (double-free, use-after-free of handles, or manual record tampering).

Solutions

Audit recent pool operations (free/forget_ticket/unsafe access) for double-free or out-of-order release.
Rebuild the pool's bookkeeping by recreating the pool instead of continuing with corrupted state.
Report it upstream with a minimal reproducer if it occurs without unsafe code — it indicates a fyrox-core bug.

Example fix

// before
unsafe { pool.records_get_mut(idx).payload = Some(obj); } // corrupts free list
pool.spawn(obj); // panics on reused record
// after
let handle = pool.spawn(obj); // use the public API

Defensive patterns

Strategy: validation

Validate before calling

// only safe API usage:
assert!(pool.try_contains(handle) || pool.is_valid_handle(handle));
// never manipulate records/free stack directly

Prevention

Use only public spawn/free APIs; never write record.payload via unsafe.
Free each handle exactly once; track freed handles.
If corruption is suspected, recreate the pool rather than continuing.

When it happens

Trigger: Calling spawn (or spawn_with directly) when the free stack contains an index whose record still holds a payload — normally only reachable through pool corruption or unsafe misuse.

Common situations: Bugs in code that manipulates the free stack or payloads directly; a double-free that pushed an index while the object was still alive; unsafe code writing payloads without updating the free stack.

Understand the failure class

Background: "This is a bug, please report it": internal invariant violations, unreachable panics, and SNH errors explained — this error's family across 47 libraries.

Related errors

AI-assisted analysis of FyroxEngine/Fyrox@76c91aad8e (2026-09-10). Data as JSON: /api/errors/64e0e05a8440ddf9. Report an issue: GitHub.

Appendix: source

Thrown at fyrox-core/src/pool/mod.rs:646

                });

                Ok(Handle::new(index, generation))
            }
        }
    }

    #[inline]
    #[must_use]
    /// Construct a value with the handle it would be given.
    /// Note: Handle is _not_ valid until function has finished executing.
    pub fn spawn_with<F: FnOnce(Handle<T>) -> T>(&mut self, callback: F) -> Handle<T> {
        if let Some(free_index) = self.free_stack.pop() {
            let record = self
                .records_get_mut(free_index)
                .expect("free stack contained invalid index");

            if record.payload.is_some() {
                panic!(
                    "Attempt to spawn an object at pool record with payload! Record index is {free_index}"
                );
            }

            let generation = record.generation + 1;
            let handle = Handle {
                index: free_index,
                generation,
                type_marker: PhantomData,
            };

            let payload = callback(handle);

            record.generation = generation;
            record.payload.replace(payload);
            handle
        } else {
            // No free records, create new one

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