Unified syscall-free heap allocator

• Type: feature
• Status: done
• Owner: Claude (Opus 4.8)
• Unblocks: feature-static-arena-profile, feature-threadsafe-io-serialization, feature-async-coroutines, feature-parallel-processing
• Opened: 2026-06-06 (from todo.md §2d / §4)

Motivation

GetMem/FreeMem/New/Dispose/ReallocMem now do real free-list reuse, but it is first-fit with an 8-byte header, no split/coalesce. Class, string, array, and raw-memory allocation should share one heap path so every target and managed value goes through the same contract.

Scope

Design: ../../developer/allocator-platform-design.md, ../../developer/garbage-collection-thoughts.md.

• Unify class/string/array/raw allocation behind one Alloc/Free/Realloc contract.
• Add alignment, block splitting, coalescing, in-place resize attempts, and size bins — after the shared path is correct.
• Keep Linux mmap/munmap as optional target hooks; bare-metal/ESP32 must not depend on them. Memory management is a per-target/per-frontend profile (ARC default · arena embedded · hosted conservative+cycle). GC never default, never bare metal.

Acceptance

Alloc/free-heavy programs reuse memory across all value kinds via the shared path; existing allocator/managed tests stay green; self-host fixedpoint holds.

Done

Commits 2a3b2f6 + f6de004. Class, string, array, and raw-memory allocation now share one pure-Pascal contract — PXXAlloc/PXXFree/PXXRealloc in compiler/builtin/builtin.pas — to which the compiler redirects GetMem/New/class-new, FreeMem/Dispose, and ReallocMem (EmitHeapAllocLocked/EmitHeapFreeLocked). mmap-backed, 8-byte size header + first-fit free list, reused blocks zeroed. Acceptance met: alloc/free-heavy programs reuse across all value kinds; full make bootstrap (byte-identical fixedpoint) + make test + make test-nilpy green.

Deferred (separate tickets, not blocking the dependents above):

• Split/coalesce/in-place-resize/size-bins/alignment → feature-allocator-quality.
• Syscall-free target-hook abstraction (mmap optional; bare-metal/ESP32) → feature-static-arena-profile (the no-syscall profile) and the ESP32 arc.

Log

• 2026-06-06 — ticket opened from todo.md §2d/§4.
• 2026-06-06 — delivered the shared pure-Pascal allocator contract (2a3b2f6, f6de004); reconstructed the lost builtin bodies and fixed the self-host regressions (not-typing, constructor-Self, nilpy fixups). Moved to done/.