From ac7223959f0a0cf94e2b409008c6ae97e3210dfe Mon Sep 17 00:00:00 2001
From: James Dansereau <106631954+jkdansereau@users.noreply.github.com>
Date: Thu, 3 Sep 2026 15:04:16 -0400
Subject: [PATCH] docs(hud): D187 finding + porting-notes D6 (missing-return /
 -O2 class)

M-47 root-cause + interactive-console verification for the missing HUD
ammo-type icon: framediff -level_09 frame 320 worst-cell dmean 21.8 -> 4.0
with the one-line AVOID_UB return; orange clip glyph confirmed present
again. porting-notes D6 covers the non-void-no-return / latent-until-O2
pattern.
---
 docs/dev/findings.md  |  1 +
 docs/porting-notes.md | 25 +++++++++++++++++++++++++
 2 files changed, 26 insertions(+)

diff --git a/docs/dev/findings.md b/docs/dev/findings.md
index e82d0c53..648a8678 100644
--- a/docs/dev/findings.md
+++ b/docs/dev/findings.md
@@ -387,6 +387,7 @@ covers D24–D69; the log continues in §H (D32 procedure, D70–D121).
 | D165 · D166 | input-layer polish (M-31, port-only, `port/src/input.c`): D165 front-end cursor is now a true ~1:1 pointer (P-controller estimating the game cursor via front.c's own integrator) instead of velocity²; D166 hipfire mouse pitch emits speed-proportional C-button pulses instead of a fixed digital threshold. | FIXED |
 | D180 · D181 | native-PC input pass (QoL run, `qol/native-pc-input-menu`): D180 = `Input.MouseCaptureMode` click-to-lock + absolute-cursor menu tracking + aim-speed default retune (`port/src/input.c`, `video.c`, port-only); D181 = `Game.ScreenShakeIntensity` route-(b) hook in `src/fr.c viShake` (`#ifdef PORT`, default 1.0 = no-op). | LANDED, config-gated, feel-checks owed |
 | D186 | **`Video.FpsCap` throttles the sim, not just presentation (M-39 diag, M-42 clamp).** The frame-pacing `sysSleep`+busy-wait in `sync_framerate_with_timer` (`port/fast3d/gfx_sdl2.cpp`) runs inline on the scheduler thread (`osSpTaskStartGo`→`gfx_run`→`swap_buffers_begin`), so a low cap blocks VI-retrace delivery and drags every game thread down to the cap rate (no N64 analogue — RSP/RDP are separate silicon). **Landed:** `0 < FpsCap < 30` → treated as `0` (uncapped) + warning, at both `videoInit` (normalises a bad `ge007.ini` for the next `configSave`) and `gfx_sdl_set_target_fps` (covers the F10-overlay live path); caps ≥ 30 unchanged. Verified: default `FpsCap=0` framediff 3/3 golden-identical; `FpsCap=10` now runs at the uncapped rate; `FpsCap=60` still paces. **Owed:** move pacing off the scheduler thread so any cap only drops presented frames. See §F "D186" + porting-notes.md §E. | CLAMP LANDED (`port/fast3d/gfx_sdl2.cpp`, `port/src/video.c`); real fix owed |
+| D187 | **HUD ammo-type/weapon icon vanished at `-O2` (M-46 root-cause, M-47 fix + verify).** `set_rgba_redirect_generate_microcode()` (`src/game/gunfire.c:5929`, sole emitter of the bottom-right magazine icon; call sites 6057/6123/6217/6219, all `gdl = f(...)`) is `Gfx *` with **no `return`** — the decomp banner above it flags exactly this. Harmless under `-Og` (GCC left the tail-call result in `$v0`); commit `34885535` (Sep 2) switched release to `-O2` → undefined return reg → callers resume the DL from the icon's start offset and overwrite its `texSelect`/`display_image` commands with the following `gunDrawHudInteger` output. Ammo *numbers* use a separate correctly-returning path — hence the exact symptom split. Fix = one line, `return` under `#ifdef AVOID_UB` (already `-DAVOID_UB=1`, `CMakeLists.txt:207`); N64 byte-match path unchanged under `#else`. **Verified M-47 (interactive console):** `-O2` build, `-level_09` `GE_PCDUMP` 200–440 — orange clip glyph absent pre-fix, present post-fix; `framediff.py` frame 320 worst-cell dmean **21.8 → 4.0**, frame 440 **21.7 → 4.6** (converges to the pre-regression golden); other levels unaffected (change is one HUD function). Do **not** revert `34885535`. | FIXED (`src/game/gunfire.c`, `#ifdef AVOID_UB`); PR #19 |
 | D152+ | D152 addendum (M-31): static audit of every compiled-audio `osSetIntMask(OS_IM_NONE)` — **all balanced**, no unbalanced early-return. Real fixes: `sndSetSfxSlotVolume` now holds the mask across its list walk (matches its twin `sndDeactivateAllSfxByFlag`) + `sndApplyVolumeAllSfxSlot` batches the slot loop under one recursive hold (kills the fade-out lock-acquire storm); `portThreadWrapper` calls `imThreadExitRelease()` on thread exit (kills the "transient thread acquired `OS_IM_NONE` and died" leak + the pthread-id-reuse re-wedge). Steal-lock kept as backstop. | FIXED (`src/snd.c`, `port/src/libultra.c`, `#ifdef PORT`) — fade-out repro playtest-gated, not headless-verified |
 | RC3 · D167 | **Non-power-of-two texture wrap period (`docs/dev/TEXTURE-GLITCH-ANALYSIS.md` §6 RC3 — "textures repeat oddly", residual Depot-ceiling noise after D161).** The N64 RDP masks the texel coordinate of a wrapping render tile at `1<<mask`, and GE sets `mask = texDimensionToMask(dim) = ceil(log2(dim))` (`src/game/tex.c:361`), so a non-PoT tile (Depot's 65×65 / 96×48 / 56×56 room surfaces) repeats at the **next power of two**, not at its image size the way GL `GL_REPEAT` does → the pattern is squashed/stretched and the seam lands in the wrong place. fast3d never stored `masks`/`maskt` at all (`gfx_dp_set_tile` dropped them) and wrapped purely at the uploaded image dimension. **Fix (`port/fast3d/gfx_pc.cpp`, behind the existing `Video.WrapFix` knob, default OFF):** store `masks`/`maskt` on the tile; in the hoisted per-texunit pre-wrap block in `gfx_sp_tri1` (D74 block — already lifted out of the vertex loop, indexed by texunit `t` not vertex `i`), when the tile is WRAP (no CLAMP/MIRROR bit) and `1<<mask != tex_width`, fold the UV at the N64 period `1<<mask` and clamp the `[dim, 1<<mask)` overflow band (which is a TMEM smear on console, no real texels) to the last texel so it reads as an edge streak instead of a bogus early image restart. `GE_WRAPFIX=0/1` env override added (env wins over the ini, matching `Debug.FrameDump`). **Per-level captures (`-level_09`/`-30`/`-34`/`-20`, WrapFix OFF vs ON, `GE_PCDUMP` 6-frame windows):** no crashes, 6/6 frames each; on settled/comparable frames Silo is ~pixel-identical (phash 0–11), Facility 180–260 pixel-identical, Depot shows small localized texel changes on ceiling/wall cells (dmean 5–9, no structural break); the large per-run deltas are all the D117 intro-camera-pan nondeterminism, not the fix. Default kept **OFF** — no regression, but a headless structural diff can't confirm the Depot ceiling actually looks *better*; needs a human eyeball with `Video.WrapFix=1`. Default-off is byte-identical to golden (all new behaviour is inside `if (g_wrap_fix)`). D74's dead in-vertex-loop wrap block was already reworked/hoisted at M-30; this only adds the mask-period trigger. Confidence: **medium** (mechanism correct; overflow-band handling is an approximation, not exact TMEM-smear emulation; visual win unconfirmed). porting-notes.md §D. | KNOB ADDED, default OFF (`port/fast3d/gfx_pc.cpp`). Needs user visual check on Depot. |
 | D168 | **`GE_PCDUMP` / F12 PPM captures were vertically flipped — the entire source of the bogus D114/D116 "HUD/text X-mirror" (M-33, developer-confirmed).** `gfx_opengl_dump_bound_fbo` (`port/fast3d/gfx_opengl.cpp`) wrote `glReadPixels` output straight to a P6 PPM. GL framebuffer origin is bottom-left; PPM P6 is top-row-first — so every capture (and the `tools_pc/golden/` set, and every screenshot pasted into the finding log since M-6) was upside-down. On real hardware / an actual screen the game renders correctly (developer confirmed). The successive D114→D116 "shared fast3d mirror" investigations — each of which found *every probed stage clean yet the output "mirrored"* — were reading an inverted capture and pattern-matching upside-down asymmetric content (text, guards, the Nintendo logo) as "mirrored". Fix: emit PPM rows bottom-to-top. `tools_pc/golden/*.png` flipped in place to match (see `tools_pc/golden/README.md`); regenerate from a real run when convenient. **Not runtime-verified this session** (no ROM / toolchain in the migrated tree — see the migration note) — needs a fresh capture to confirm text reads normally. Confidence: **high** (mechanism is unambiguous; developer has hardware confirmation the screen is correct). porting-notes.md §D2. | FIXED (`port/fast3d/gfx_opengl.cpp`); D114 / D116 reclassified as capture-orientation artifacts (below). |
diff --git a/docs/porting-notes.md b/docs/porting-notes.md
index bc782a40..1642163e 100644
--- a/docs/porting-notes.md
+++ b/docs/porting-notes.md
@@ -581,6 +581,31 @@ past it (walk off the end).
   any `for`/`while`/`do` whose end pointer is the address of a *different*
   symbol than the one being iterated.
 
+## D6. Non-void function with no `return` — latent until `-O2`
+
+The decomp has a handful of functions declared to return a value (often
+`Gfx *`) whose body ends without a `return` — the IDO/N64 build happened to
+leave the intended value in `$v0` (usually the result of a tail call), and
+the caller's `x = f(...)` kept working by luck. GCC on the PC target does
+too **at `-Og`**, but at **`-O2`** the return register is genuinely
+undefined and the caller reads garbage. When the value is a display-list
+cursor, the caller then keeps writing the DL from a stale offset and
+overwrites whatever the function just emitted — the emitted primitive
+silently disappears.
+
+- Instance: **D187** — `set_rgba_redirect_generate_microcode()`
+  (`src/game/gunfire.c`), the sole emitter of the HUD ammo-type icon.
+  Invisible under `-Og`; vanished the day release switched to `-O2`
+  (`34885535`). Fix: `return` the tail call under `#ifdef AVOID_UB`
+  (`#else` keeps the N64 body verbatim).
+- The one currently flagged in-source is `grep -rn "missing a \"return\"" src/`
+  (just `gunfire.c` today). Others may exist without the banner — suspect this
+  class whenever an `-O2` build drops a small on-screen element that an `-Og`
+  build shows. One-line `#ifdef AVOID_UB` fix each.
+- Not caught headless by a symbol/link check or a default-config framediff
+  (the missing primitive is often small). Needs an `-O2` build + an eyeball
+  or a targeted crop diff.
+
 ## E. Process / method notes
 
 - Investigation loop is: reproduce → env-gated capped probe → root-cause