Allocation, arenas, reference counts, and cycles

AIF chooses a management strategy; the runtime implements strategies that need dynamic support. runtime/lang_runtime.c contains allocation bookkeeping, region chunks, unique release, reference counts, and cycle-management machinery.

Regions

T1 regions use aligned bump allocation from linked chunks. A region exit reclaims its chunks together, and a small pool can retain default-sized chunks for reuse. Oversized chunks are returned. Growing a region-backed list allocates another buffer without reclaiming the previous capacity until the region ends.

Unique and shared storage

T2 storage has one owning path and deterministic release. T3 storage adds reference-count metadata for shared acyclic values. Cycle-capable storage adds candidate and traversal state for graphs that plain counts cannot reclaim.

The current ambient arena and cycle state includes process-global mutable data. Native task use therefore has correctness work remaining; thread-local or synchronized state and stress coverage must precede performance conclusions.

Verification

--verify records selected allocations, releases, leaks, and violations. Arena statistics are partly separate, and ordinary benchmark output does not yet provide unified per-site byte, high-water, lifetime, copy, or reference-count telemetry.

Do not present “zero leaks” as complete memory proof. Foreign allocations, platform handles, premature balanced releases, and concurrency races require additional tests and tools.

Base allocator and pools

rt_base_alloc and rt_base_realloc are no-inline allocation boundaries so verifier, profiling, and native instrumentation can observe them. rt_pool_put_or_free returns eligible blocks to the runtime pool and otherwise calls the platform allocator. rt_free is the matching release. rt_alloc checks whether a runtime allocation should follow the active arena hint.

The verifier replaces the base path with aif_verify_alloc, aif_verify_realloc, and aif_verify_release. Its ledger hashes live pointers, stores sizes/state, poisons released storage, and reports duplicate/invalid releases. aif_verify_usable_size supports realloc and container growth without losing accounting.

Arenas

arena_push creates a dynamic region frame. arena_chunk_new allocates the first or next chunk sized for the requested object. arena_alloc_slot performs aligned bump allocation in a specific frame; arena_alloc uses the current frame and arena_alloc_at uses an explicit slot chosen by AIF. arena_pop frees all chunks owned by the frame at once.

arena_current_slot, arena_objects, and arena_regions expose runtime counters. rt_arena_hint_push and rt_arena_hint_pop let call-produced values use the active region even when allocation occurs inside a runtime helper such as string concatenation.

Every return, break, continue, and early branch leaving a region must emit the matching pop. Individual arena objects must not enter ordinary drop lists.

Reference counting

rc_alloc reserves a header immediately before the user pointer and initializes the count. rc_slot recovers it. rc_retain increments, while rc_release decrements and frees on zero. rc_attach_cold associates hot/cold split storage so the final release reclaims both records; rc_cold_slot locates that companion.

rc_retain_atomic and rc_release_atomic are the cross-thread variants. AIF's thread domain selects them only when overlap is possible. Using atomics for every value would be safe but would erase an intended optimization; using non-atomic operations for a shared value is incorrect.

Cycle collection

cyc_alloc creates a colored RC header. cyc_set_type installs two generated callbacks: one enumerates cyclic child edges and one releases the concrete object. cyc_retain and cyc_release maintain the count and buffer possible roots.

The collector follows the trial-deletion phases:

• cyc_mark_grey subtracts internal references through the visitor;
• cyc_scan identifies zero-count candidates;
• cyc_scan_black restores live subgraphs;
• cyc_collect_white reclaims the unreachable cycle; and
• cyc_free_object runs the typed release path.

cyc_collect processes buffered roots, cyc_collect_now provides an explicit test boundary, and cyc_final performs final cleanup. cyc_objects, cyc_reclaimed, and cyc_collections_run expose evidence counters. Platform mutex helpers protect collector state when memory threading is enabled.

Tests must build acyclic and cyclic graphs, retain a live cycle through an external root, break an edge, collect explicitly and at shutdown, exercise recursive payloads and hot/cold fields, and run cross-thread stress under TSan.