BT411/context/build-and-run.md

---
id: build-and-run
title: "Build / Run / Debug — recipe, repo layout, env gates"
status: established
source_sections: "PROGRESS_LOG.md §10a, §10a-bis; README.md"
related_topics: [wintesla-port, decomp-reference, reconstruction-method]
key_terms: [BTL4OPT, cdb, BTL4.RES, EGG, WinTesla]
---

# Build / Run / Debug

The one top-level `CMakeLists.txt` builds `munga_engine` (engine) + `bt410_l4` (reconstructed BT
game lib) + `btl4.exe`. Full recipe + repo-layout map: `docs/PROGRESS_LOG.md §10a / §10a-bis` +
`README.md`. Env-gate table: [[decomp-reference]] §6.

## Build (Win32 / VS2022 BuildTools — the DXSDK link libs are Lib/x86)
```
# configure once (BT412 toolchain of record, moved from VS2019/v142 at the 4.12 fork):
cmake -S . -B build -G "Visual Studio 17 2022" -A Win32 \
  -DCMAKE_GENERATOR_INSTANCE="C:/Program Files (x86)/Microsoft Visual Studio/2022/BuildTools"
# build:
cmake --build build --config Debug
```

### Build flavors — the `BT412` compile gate (2026-07-17, merge-back into BT411)
One tree builds both lines; `option(BT412 ... ON)` gates the steamification layer. [T2]
- **Default (`BT412=ON`)** — pod/dev game + PadRIO/plasma/front end/lobby (all runtime-gated;
  a `-egg`/`-net` launch behaves as 4.11). Compile definition `BT412` set on all 3 targets.
- **Pod-minimal (`-DBT412=OFF`, dir `build-pod/`)** — compiles OUT `L4PADRIO`, `L4PADBINDINGS`,
  `L4KEYLIGHT`, `L4PLASMASCREEN`, `L4STEAMTRANSPORT`, `btl4fe`, `btl4console`, `btl4lobby`.
  Seam sites carry `#ifdef BT412`: `L4CTRL.cpp` PAD token (log + ignore), `L4GREND.cpp`
  `L4PLASMA=SCREEN` (log + ignore), `L4VB16.cpp` (inert `PadRIO` stub struct — call sites
  identical in both flavors), `btl4main.cpp` (front-end/marshal/lobby blocks compile out;
  zero-arg launch = 4.11 behavior). The **NetTransport seam always compiles** — it is the wire
  for both flavors (`WinsockNetTransport` verified byte-identical to pre-seam arcade behavior).
  Verified: clean v143 link (no unresolved), solo `-egg DEV.EGG` runs (31 subsystems tick, gait,
  targeting).
- **Steam (`-DBT412_STEAM=ON`, dir `build-steam/`)** — requires `BT412=ON` (configure-time
  `FATAL_ERROR` otherwise; negative-tested).
- Links DXSDK d3d9/d3dx9/dinput8 + OpenAL/libsndfile (`engine/lib/`). DXSDK June 2010 at
  `C:\Program Files (x86)\Microsoft DirectX SDK (June 2010)\` (overridable `-DDXSDK`). [T2]
- Linker uses **`/FORCE:MULTIPLE`** — tolerates the ~124 header-defined-global LNK2005s.
  **`UNRESOLVED` is gone (BT412, 2026-07-14):** the v143 linker refuses to emit an image with
  unresolved externals even under `/FORCE`, so the dead offline-tool ladders in `mech3.cpp`
  (`Mech::CreateSubsystemStream` / `Mech::SubsystemDefaultData` — never called at runtime) are
  compiled out behind `BT412_OFFLINE_TOOLS` (default off). A genuinely unresolved symbol is now a
  hard LINK ERROR, not a hidden runtime AV — the [[reconstruction-gotchas]] §6 hazard class is
  retired for the exe link. No other source changes were needed for v143 (verified: clean build,
  solo DEV.EGG run, two-instance loopback MP with replication). [T2]
- Editing an `engine/` file rebuilds the engine lib automatically (one project). A NEW member on a
  `DPLRenderer`/`d3d_OBJECT` class needs the game objs that embed its layout recompiled — delete
  stale objs if layout-mismatch corruption appears. [T2]
- ⚠ Kill the running exe before rebuilding (`taskkill //F //IM btl4.exe`) or you get LNK1104.

## Run
```
run\run.cmd [EGG]      # default DEV.EGG; cd's to content\ and runs btl4.exe -egg <EGG>
```
- **cwd MUST be `content\`** — the engine resolves `BTL4.RES`, `VIDEO\`, `BTDPL.INI`, eggs relative
  to cwd (the `loadTables` gotcha: `L4VIDEO.cpp:849` `fopen("VIDEO\\REPLACEMATS.tbl")` is relative +
  unchecked → fread on NULL if cwd is wrong). Logs to `btl4.log` in `content\` (or `BT_LOG=<file>`). [T2]
- Interactive: **WASD** drive; weapon groups (keyboard, task #43) **1/Space** = lasers, **2** =
  PPCs, **3/Ctrl** = missiles; **X** all-stop; **V** cockpit/chase view. Default egg = `DEV.EGG`
  (map=grass, time=day). Swap mech via the egg's `vehicle=` (bhk1/madcat/…). The code path is
  mech-agnostic (verified — Mad Cat booted + fought with zero code changes). [T2]

## Debug (cdb x86)
`"C:\Program Files (x86)\Windows Kits\10\Debuggers\x86\cdb.exe"`. Pattern for a faulting stack (cwd
= content\): `-g -c ".lines;sxe av;g;kp 24;q"` with `BT_ASSERT_TO_DEBUGGER=1`. Debug CRT fills fresh
heap **0xCDCDCDCD** (uninit) + freed **0xFEEEFEEE** — invaluable for "was this ever constructed?".
`BT_HEAPCHECK=1` = whole-heap validation every alloc/free (O(n²) at mission load — SLOW). To attach
to a frozen abort dialog: `cdb -p <pid> -c ".lines;~*kp 30;q"`. [T2]

## Repo layout (bt411)
- **`engine/MUNGA/` + `engine/MUNGA_L4/`** — the shared 2007 MUNGA engine + Win32/D3D9 HAL (carries
  our BT render/loader work: bgfload/L4D3D/L4VIDEO + the image codec). `engine/shim/` (ATL),
  `engine/lib/` (OpenAL/libsndfile), `engine/rp/` (RP *headers* the audio HAL includes).
- **`game/reconstructed/`** — the reconstructed BT source (the bulk).
- **`game/original/BT/` + `BT_L4/`** — surviving original BT `.cpp` + **all BT headers** (the include path).
- **`game/fwd/`** — ~186 forwarding shims (`#include <EXPLODE.hpp>` → `../../engine/MUNGA/<NAME>.h`).
- **`game/btl4main.cpp`** — the WinMain launcher.
- **`content/`** — the runtime tree (BTL4.RES, VIDEO/, GAUGE/, AUDIO/, eggs, BTDPL.INI). Run cwd.
- **`reference/decomp/`** — the raw Ghidra pseudocode (`all/part_*.c`) — the source-of-truth.
- **`docs/`** — the detailed ledgers (incl. `PROGRESS_LOG.md`, the full pre-restructure CLAUDE.md).
- **`tools/`** — btconsole.py, disas2.py, map/res scanners. **`context/`** — this knowledge base.

## Key Relationships
- Base: [[wintesla-port]] (the engine build recipe).
- Verify loop: [[reconstruction-method]]; env gates: [[decomp-reference]] §6.