rt: exact-size heap bounds; n, the words new asked for, lives in bits 32..62 of p[-4]

2026-10-14T15:05:03+00:00

the bnd recipe and paylen read n instead of the power-of-two block: bnd: r6 = sub p 3; r6 = ld r6; r7 = xor p 0x2B7E1516; r6 = eq r6 r7; r7 = sub p 4; r7 = ld r7; r7 = shr r7 32; r7 = mul r7 q; r8 = mul i m; r8 = ltu r8 r7; r8 = xor r8 1; r0 = and r6 r8 paylen: return p[-4] >> 32 two loads instead of three; osize, bchk, release, recycle and the memdebug leak report all read n (rt.new(4) has length 4, rt.new(0) has 0). writers: new_raw and new_k set n; stack.h line 87 and tinyvm.ts (BigInt) set it on stack segments. release clears n when a block goes into quarantine (len 0, indexing traps; under memdebug bchk reports a use after free); every free-list path (fpush, mkblock, bdrop, recycle_leaf, balloc hold) rewrites the word as k << 16, and an array that grows gets a fresh block. a request over 2^31-1-HDR words stops in new_raw (oom), and the compiler only takes the new_k fast path for constant sizes that fit, so n is never truncated. bit users checked (all mask or preserve bits 32..62; none compares or copies the whole word): gc mark and sweep; release, free, recycle, recycle_leaf; share and own; isobj, quar, checkptr, obj_base; bclass and the bfree buddy merge; balloc, mkblock, fpush, funlink, heap_grow; frame_grow; stack_allocate in src/core/stack.h and src/js/tinyvm.ts; micro.c and core.c (check word only); the compiler's two p[-4] | F_INTERNAL writes (base.zc, builtins.zc). 32-bit ports: none (baremetal, wasm and micro use int64 Cell). tests: tests/programs/exactsize.zc (n-1/n for non-power-of-two sizes, new(0), packed bytes, recycle, grow, stack growth); 8-runtime: exact_size_bounds, pointer_index_n_minus_1, pointer_index_n_traps, pointer_index_n_traps_memdebug, new_zero_index_traps, new_too_big_traps, stale_index_after_free_traps, stale_index_after_free_memdebug. expectations changed: leak report shows n (tests/test.sh line 169, examples/learn/13-memdebug.out, docs/LEARN.md, 4-statements/memdebug_report_line.zc). programs adjusted to keep test.sh expectations: quarantine.zc (unbounded), bounds_heap.zc (rt.new(11)). spec 3.7.4 and 4.11 updated. fixpoint 402204 words (main 402197).

bounds checking: port agent/bounds-checking onto main 0879d0a; unbounded main in o3call, o3 tests expect no check, boundsrules, bounds_fixed, bounds_heap and zc0unbounded tests

2026-10-14T12:28:58+00:00

moon/zygotec/tests/programs/bounds_heap.zc, branch work/b213

rt: exact-size heap bounds; n, the words new asked for, lives in bits 32..62 of p[-4]

bounds checking: port agent/bounds-checking onto main 0879d0a; unbounded main in o3call, o3 tests expect no check, boundsrules, bounds_fixed, bounds_heap and zc0unbounded tests