totk-pc-recomp/docs/building.md

Building from source

Windows 10 or later, an x86-64 CPU with AVX2, and a GPU with Vulkan 1.3 and VK_EXT_external_memory_host. Allow about 60 GB for the work folder. Extraction wants about 55 GB free while it runs and keeps about 35 GB afterwards.

Players who only want to play can use the installer instead: it builds the game on their machine without this toolchain.

Toolchain

Versions are the ones the build was verified with; newer patch releases are fine.

Tool	Version	Install	Used for
MSYS2 UCRT64	clang/lld 23.1.3	msys2.org installer to C:\msys64, packages below	compiling the generated C and the runtime
Visual Studio Build Tools	2026, C++ workload, Windows SDK 10.0.26100	winget Microsoft.VisualStudio.BuildTools with --add Microsoft.VisualStudio.Workload.VCTools --includeRecommended	the linker .NET NativeAOT calls
.NET SDK	10.0	winget Microsoft.DotNet.SDK.10	the shader translator (totk_xlate.exe)
Vulkan SDK	1.4.363	winget KhronosGroup.VulkanSDK	validation layers, vulkaninfo
uv	0.13	standalone installer from astral.sh	the two Python environments
hactool	1.4.0 @ 1d64a83	.venv\Scripts\python tools\build_hactool.py, see below	NCA and update extraction

MSYS2 packages, after pacman -Syuu (run it twice; the first pass updates the core and exits):

pacman -S --needed --noconfirm mingw-w64-ucrt-x86_64-{clang,lld,ninja,gcc,make,pkgconf,sdl3,opus,libvpx,zstd,vulkan-devel,\
vulkan-memory-allocator,vulkan-validation-layers,shaderc,spirv-tools} base-devel git unzip

ffmpeg from MSYS2 is a GPLv3 build and is never linked; the movies go through libvpx.

PATH:

• Add C:\Program Files (x86)\Microsoft Visual Studio\Installer to the user PATH: NativeAOT needs vswhere.exe, or the publish fails at the link step (MSB3073).
• Another cmake or ninja earlier on PATH (a 32-bit winlibs MinGW, for example) is picked up by accident. The build scripts call Ninja from C:\msys64\ucrt64\bin themselves; from a shell, put C:\msys64\ucrt64\bin first.

hactool

tools/build_hactool.py fetches SciresM/hactool at 1d64a83 into toolchain\src\hactool, applies the two patches in tools/hactool/ and builds a static toolchain\hactool\hactool.exe with MSYS2 UCRT64 gcc (a few seconds):

• portable.patch: the parts of MacNativeGames' build_hactool() that run on Windows, the MNG_TITLE_KEYS variable and the two BKTR fixes in nca.c for the subsection table padding and the subsection layout of newer cumulative updates;
• unicode.patch: a manifest with <activeCodePage>UTF-8</activeCodePage>, so paths under a non-ASCII user profile reach it intact.

hactool reads -k <prod.keys>; MSYS2 shells set HOME, which hides its default key location, so pass -k there.

Build

From the repository root, in PowerShell. Every step that depends on the game version takes it as <ver>: v143 for 1.4.3 or v121 for 1.2.1. The tools default to v121 when --version is left out. Saves load on either version.

1. Python environments (once). .venv runs the lifter and the build; .venv-py314 runs the extraction scripts, which need the stdlib compression.zstd of Python 3.14:

   uv venv --python 3.12 .venv
   uv pip install --python .venv/Scripts/python.exe -r tools/requirements.txt
   uv venv --python 3.14 .venv-py314
   uv pip install --python .venv-py314/Scripts/python.exe -r tools/requirements-py314.txt
   

2. Copy config.example.toml to config.local.toml and set the paths to your base game, the update and your console's keys file. config.local.toml is ignored by git. The tools read the keys file themselves.

3. Extract and verify. This writes build\extracted\v0 (1.0.0) and build\extracted\<ver> for each update in updates, identified by its hash; a hash mismatch stops the run:

   .venv-py314\Scripts\python tools\extract.py
   

4. Shader translator (once; no game files). This publishes build\xlate\totk_xlate.exe:

   .venv\Scripts\python tools\build_xlate.py
   

5. Lift the modules to C, write the RomFS half of the frame-rate patches, then compile and link build\<ver>\totk.exe:

   .venv\Scripts\python recomp\gen.py --exefs build\extracted\<ver>\exefs --out generated\<ver> --patches recomp\patches-<ver>.txt
   .venv-py314\Scripts\python tools\make_romfs_patches.py --version <ver>
   .venv\Scripts\python tools\build_game.py --version <ver>
   

   Lifting takes about 15 s, a clean compile about 200 s on 24 threads; later builds recompile only what changed. A compiler cache in front of clang shortens it further: with SCCACHE set to an sccache executable, build_game.py writes it into the ninja file ahead of cc, and every lift rewrites the generated chunks with the same contents, so a second build of the same version hits all of their objects:

   $env:SCCACHE = "path\to\sccache.exe"
   .venv\Scripts\python tools\build_game.py --version <ver>
   

   --patches builds in the frame-rate, resolution and other patch sets, switchable at run time. The link copies SDL3.dll, libiconv-2.dll and libopus-0.dll next to the exe. For Xbox button prompts, run make_romfs_patches.py once more with --xbox-prompts: it writes build\<ver>\romfs-patches-xbox (controls.md, "Xbox button prompts"); build_game.py copies it next to totk.exe like romfs-patches.

6. Prepare the shaders (once per build folder and translator). It needs refs\MacNativeGames (tools\fetch_refs.sh) for the shared shader list:

   .venv-py314\Scripts\python tools\prepare_shaders.py build\<ver> --version <ver>
   

   Without this step the first launch compiles shaders and pipelines during play and stutters until the caches fill. The AMD driver keeps its pipeline cache per exe path and holds a limited amount: preparing another build folder can evict this one's. totk.exe --warm-shaders rebuilds it from the shader cache.

7. Run. The game pauses while its window is out of focus, as it does on the Switch when Home is pressed; assume_focus = 1 in totk.ini, or the Game tab, keeps it running in another window.

   build\<ver>\totk.exe
   

Settings live in totk.ini next to totk.exe (totk.ini.example lists them). Saves go to build\profile for v121 and build\profile-<ver> for other versions (build_game.py --profile changes it).

Portable folder

.venv\Scripts\python tools\package_build.py --version <ver> writes build\<ver>-portable, which runs on another of your machines without MSYS2, Python or .NET. romfs.bin stays out unless you pass --with-romfs; otherwise put it in romfs\ next to the exe or point TOTK_ROMFS at its folder. Run totk.exe --prepare-shaders once in the copied folder. The folder holds code and data derived from your game: for your own machines only.

Checks

Before a commit:

• python tools/check_content.py --staged: nothing game-derived is staged. CI runs the same check; git config core.hooksPath .githooks runs it before each local commit.
• build\<ver>\totk.exe --selftest: layout, dispatch table and host-function registry, without game files.

The lifter (recomp/) and the CPU headers (runtime/cpu.h, runtime/simd.h) are checked against Unicorn. Every lifter change passes these, all run with .venv:

Test	Checks	Game files
tests\diff\lift.py	instructions sampled from the extracted modules; --coverage lists every word the lifter rejects or traps	yes
tests\diff\simd.py	the whole FP/SIMD encoding space	no
tests\diff\atomic.py	exclusive load/store sequences and ARMv8.1 atomics	no
tests\diff\func.py	whole functions as the generator emits them, loops, jump tables and calls included (calls go to a stub that checks the registers at the call)	yes
tests\flags_check.py	the function-local flag helpers of runtime\cpu.h against its packed ones	no
tests\excl_mt.py	the exclusive monitor helpers under contention and ABA, on several threads	no
tests\jumptables_check.py	recomp/jumptables.py against a Unicorn oracle; must report 0 disagreements, on 1.4.3 too	yes

Runtime probes, each a mode of totk.exe (the list is at the top of runtime/main.c): --probe-kernel, --probe-vkexec, --probe-nvn-tex and --probe-shader cover most runtime changes.

Shaders: .venv-py314\Scripts\python tools\shader_census.py --version <ver> --translate extracts every Maxwell shader to build\<ver>\shaders\ and runs it through the translator and spirv-val; failure groups go to failures.txt. tools\xlate_smoke.py checks the translator alone, without game files.

Reverse engineering (optional)

• Ghidra 12.1.2 with Adubbz's Ghidra-Switch-Loader in toolchain\ghidra\ (JDK 21) opens the game modules (NSO).
• tools\fetch_refs.sh clones the upstream projects this port builds on into refs\, read-only.