meta_slot

Summary. Load the originating transaction's metadata object into a slot.

Signature.

int64_t meta_slot(uint32_t slot_no);

Parameters.

Name	Type	Description
slot_no	uint32_t	Destination slot, or 0 to allocate a free slot.

Return value. Returns the slot number the metadata was loaded into on success. Errors: PREREQUISITE_NOT_MET (-9) if metadata is not available in the current execution; INVALID_ARGUMENT (-7) if slot_no exceeds max_slots; NO_FREE_SLOTS (-6) if slot_no == 0 and none are free.

Common failure patterns.

• Calling it when no provisional metadata exists → PREREQUISITE_NOT_MET. Transaction metadata only becomes available once the transaction has been applied, so this is aimed at weak (post-apply) executions; see hook_again.

Caveats / notes.

• The slotted object is the transaction's TxMeta; drill into it with slot_subfield / slot_subarray the same way as any other slotted object.
• meta_slot is available without an amendment gate in this branch.

Minimal example.

int64_t m = meta_slot(0);   // PREREQUISITE_NOT_MET during a strong (pre-apply) execution

Related APIs. hook_again, slot_subfield, xpop_slot.