Robert Allan JamesandClaude Sonnet 5
91f7b39d3c
Confirmed the exact mechanism behind the aarch64-specific D+/D. divergence
found in the std79 exerciser campaign (commit cc81edf). The earlier
writeup's cell_t-width check was real but answered the wrong question --
cell_t is 64-bit everywhere, but double_word_d_plus()'s carry-detection
casts through plain `unsigned long`, and sizeof(unsigned long) is 4 (32-bit)
on this aarch64 bare-metal cross-compile target specifically (amd64 and
riscv64 both happen to have a 64-bit long). The low-cell addition silently
truncates to 32 bits, then widens back to cell_t via ordinary (non-sign-
extending) conversion, producing a wrong positive result_low whenever the
true 64-bit sum is negative -- confirmed live by splitting result_low into
hi/lo 32-bit halves: the real pushed value for `-5 S>D 3 S>D D+` is
+4294967294, not -2. D.'s overflow check is correct and is faithfully
reporting a genuinely malformed double; D+ is the actual defect.
vm.h already defines ucell_t for exactly this class of problem (same
conditional as cell_t, guaranteed width-matched on every target) --
print_number_formatted() (format_words.c) already uses it correctly, D+
doesn't. Also flagged (not exercised by the campaign, same bare-`unsigned
long` pattern, same latent risk): D-, DNEGATE, and the d_compare() helper
behind DMAX/DMIN/D</D=.
Report only, per this project's standing rule (report bugs, don't fix
without being asked) -- no source change in this commit, debug probes
added during the investigation were reverted after use.
Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01EXieurDfDSsDFdnSyusuWo
capsules/
FORTH personality files loaded by the VM at boot. A capsule is an immutable, content-addressed payload; its XXHash64 hash is its identity. Any mutation changes the hash and the birth protocol rejects the image.
Key files
| File | Type | Purpose |
|---|---|---|
init.4th |
(m) MAMA_INIT |
Default Mama VM personality — loaded at LBN 2048 |
ACL.4th |
user | Word-level ACL system; self-activating at boot |
zuse.4th |
user | Bootstrap superuser; loaded by ACL.4th |
doe.4th |
user | DoE workload words (EXEC-DOE) — opt-in |
init-0.4th … init-9.4th |
(p) |
Numbered personality variants |
init-l8-*.4th |
(p) |
L8 Jacquard mode variants (stable/volatile/diverse/temporal/transition/omni) |
hermes/init.4th |
(p) |
Hermes baby VM personality |
artemis/init.4th |
(p) |
Artemis baby VM personality |
Block namespace
Block ranges are shared across all loaded capsules — collisions cause silent word-definition overwrites.
| Range | Owner |
|---|---|
| 2048–2099 | init.4th |
| 2100–2199 | doe.4th |
| 3000–3999 | workload capsules |
| 4000+ | user-defined (ACL.4th, zuse.4th, …) |
Each block is limited to 1024 bytes. Verify with wc -c before committing.
See also
experiments/bare_metal/README.md— DoE protocols and block namespace rulesdocs/03-architecture/word-acl/DESIGN.md— ACL system designtools/mkcapsule.c— assembles capsules intocapsule_generated.c- Project root