mtgodot-poc/docs/THIRD-PARTY.md

# Third-party native dependencies

The GDExtension links five native libraries that are **not** part of Godot or
godot-cpp. Phase 1 (macOS) pulled the first three from Homebrew; that stops
working the moment we cross-compile for the Android NDK or the iOS SDK (BACKLOG
F1/F2), so as of 2026-08-30 they are built from source as part of our own CMake
build. Crypto++ joined later (2026-09-02) with the `MT_PROTOCOL=classic` 40250
backend and was vendored the same way from the start.

CPython joined on 2026-09-23 with 批次 2P (the embedded 40250 script layer) and is
vendored source as well. FreeType joined the same day with 批次 2V0-g (the 40250
font path over an emulated GDI).

Everything lives under `extension/third_party/` and is wired by
`extension/third_party/CMakeLists.txt`, which exposes five aliases:

| Alias             | Backing target   | Consumed by                        |
|-------------------|------------------|------------------------------------|
| `mt3p::sodium`    | `sodium`         | `mtnet`, `mtpack`, `mtproto`       |
| `mt3p::zstd`      | `libzstd_static` | `mtpack`                           |
| `mt3p::minilzo`   | `minilzo`        | `mtproto`                          |
| `mt3p::cryptopp`  | `cryptopp`       | `mtnet` (classic backend)          |
| `mt3p::python`    | `mtpython`       | the script layer (`py_embed_test`) |
| `mt3p::freetype`  | `freetype`       | `port_platform` (`platform/Win32Gdi.cpp`) |

No source file changed: `#include <sodium.h>`, `#include <zstd.h>`,
`#include <lzo/lzo1x.h>` and `#include <cryptopp/…>` all still resolve (the LZO
one via a 1-line shim header, see below).

## libsodium — via `robinlinden/libsodium-cmake`

* **Submodule:** `extension/third_party/libsodium-cmake` @ `9b2848d`
  * itself carries `jedisct1/libsodium` @ `93a7d0d` (libsodium 1.0.20 line) as a
    **nested** submodule — clones need `--recursive`.
* **Why the wrapper:** upstream libsodium is autotools-only. This MIT-licensed
  wrapper is a pure CMakeLists over an untouched libsodium checkout; it generates
  `version.h`, sets `CONFIGURED`, and builds clean for macOS / iOS / Android /
  Windows. Used by many mobile projects.
* **Build options we force:** `SODIUM_DISABLE_TESTS=ON`, `SODIUM_MINIMAL=OFF`
  (we need `crypto_kx`, `crypto_auth`, `crypto_aead_xchacha20poly1305`,
  `crypto_stream_xchacha20`, `crypto_generichash`/BLAKE2b — all outside the
  "minimal" set).
* **License:** ISC (libsodium) + MIT (wrapper). Ship-safe.

## libzstd — `facebook/zstd`

* **Submodule:** `extension/third_party/zstd` @ tag **v1.5.6** (`794ea1b0`).
* Built through upstream `build/cmake` with:
  `ZSTD_BUILD_PROGRAMS/SHARED/TESTS/CONTRIB=OFF`, `ZSTD_BUILD_STATIC=ON`,
  `ZSTD_LEGACY_SUPPORT=OFF`, `ZSTD_MULTITHREAD_SUPPORT=OFF` (the eterpack path
  only does single-shot `ZSTD_compress`/`ZSTD_decompress`).
* Target consumed: `libzstd_static` (carries its own public include dir).
* **License:** BSD-3-Clause / GPLv2 dual. Ship-safe under BSD.

## miniLZO — vendored source (not a submodule)

* **Files:** `extension/third_party/minilzo/{minilzo.c,minilzo.h,lzoconf.h,lzodefs.h}`
  copied verbatim from **lzo-2.10** (`minilzo.c` sha1 `019debb3…`), plus
  `README.LZO`, `COPYING`, `AUTHORS` as required by the LZO license.
* Upstream LZO has no git repo (oberhumer.com tarball only), and miniLZO is a
  4-file amalgamation, so it is copied in rather than submoduled.
* **Shim:** `minilzo/lzo/lzo1x.h` is a 1-line `#include "../minilzo.h"` so
  `extension/src/proto/proto.cpp` keeps `#include <lzo/lzo1x.h>` unchanged.
  miniLZO's API (`lzo_init`, `lzo1x_decompress_safe`, `LZO_E_OK`, `lzo_uint`) is a
  strict subset of full LZO and covers everything the CLZO path uses.
* **License:** **GPLv2**. Acceptable for this internal, non-published,
  non-commercial project on the same footing as `libgr2/src/oodle1.c` — but LZO
  must be removed, replaced, or commercially licensed before any public release
  or commercial use. (item_proto/mob_proto are the only LZO consumers; a
  clean-room LZO1X decompressor is the eventual fix.)

## Crypto++ — vendored source (not a submodule)

* **Files:** `extension/third_party/cryptopp/` (~6.6 MB), copied from the 40250
  client tree (`ClientVS22/extern/include/cryptopp`), `CRYPTOPP_VERSION 840` =
  **8.4.0**. The 40250 server links this exact version
  (`Server/.../extern/cryptopp_8_4_0.tar.gz`), so the version is pinned by
  wire compatibility, not preference.
* **Why:** the `MT_PROTOCOL=classic` backend's `_IMPROVED_PACKET_ENCRYPTION_`
  cipher — DH2 key agreement + hint-selected block ciphers (Twofish default) in
  CTR mode. Only consumer is `extension/src/net/classic/classic_cipher.{h,cpp}`.
  The m2dev backend does not use it (that one is libsodium/XChaCha20).
* **No upstream CMakeLists**, so `cryptopp/CMakeLists.txt` is ours: it globs the
  library TUs and drops the cryptest / benchmark / adhoc / FIPS-selftest ones
  (`adhoc`, `bench1..3`, `datatest`, `dlltest`, `fipsalgt`, `fipstest`, `pch`,
  `regtest1..4`, `test`, `validat0..10`).
* **ASM disabled everywhere** (`CRYPTOPP_DISABLE_ASM` / `_SSSE3` / `_AESNI`) so
  one pure-C++ build works on macOS, the Android NDK and the iOS SDK; the classic
  cipher needs no AES-NI / SHA-ext. Android additionally compiles the NDK's
  `sources/android/cpufeatures/cpu-features.c` in, because upstream `cpu.cpp`
  includes `cpu-features.h` unconditionally under `__ANDROID__`.
* Built with `-w` (upstream is not warning-clean under `-Wall`) and
  `-fno-strict-aliasing`.
* **License:** **public domain** — the compilation carries Wei Dai's copyright,
  but every individual file is placed in the public domain by its authors
  (`extension/third_party/cryptopp/License.txt`). Ship-safe; unlike miniLZO it
  imposes no obligation before a public or commercial release.

## CPython 2.7.18 — vendored source (not a submodule)

* **Files:** `extension/third_party/cpython-2.7.18/` (~25 MB), the official
  `Python-2.7.18.tgz` (sha256 `b62c0e7937551d0cc02b8fd5cb0f544f9405bafc9a54d3808ed4594812edef43`)
  trimmed of what an embedded interpreter never builds or ships: `Doc Demo Tools
  Mac PCbuild`, `Modules/{_ctypes,expat,zlib,_sqlite}`, the stdlib test trees and
  the pre-VS2010 `PC/` project files. `Lib/` stays: the `mtpython_stdlib` target
  packs it into `<build>/python27.zip` with `tools/py_embed/make_stdlib_zip.py`,
  which is what the host puts on `sys.path` (batch 2P step 3). Entries are
  **stored, never deflated** — the `zlib` module is trimmed out above, so
  `zipimport` has nothing to inflate with. The zip and its `.sha256` are copied
  into `project/` (gitignored) so the exporter packs them; on Android/iOS
  `extension/src/python_stdlib.cpp` stages the zip out of the PCK into `user://`
  and checks that digest, because CPython opens it with its own stdio.
* **Why vendored:** 2.7 is end-of-life, so there is no package to fetch on the
  four target SDKs, and the build must keep working offline and on the
  cross-build machines. It is the version the 40250 scripts are written for
  (`ScriptLib` embeds 2.7), so it is pinned by the scripts, not by preference.
* **Built by our own `cpython-2.7.18/CMakeLists.txt`**, not autotools: one
  `mtpython` static library from the exact 133 objects the reference
  `libpython2.7.a` contains. The source list and the built-in module table
  (`config/config.c`, `config/Setup.static`, 39 entries) are **shared**;
  `pyconfig.h` is **not** — it is a probe result, so each platform keeps its own
  under `config/<platform>/`, regenerated by `tools/py_embed/gen_pyconfig.sh`.
  Off by default: `-DMTGODOT_EMBED_PYTHON=ON` builds it.
* **Three vendor patches** (everything else is verbatim upstream):
  1. `configure` + 2. `configure.ac` — add `arm64) MACOSX_DEFAULT_ARCH="arm64"`
     to both `case \`/usr/bin/arch\`` blocks; upstream predates Apple silicon and
     dies with "Unexpected output of 'arch' on OSX".
  3. `Modules/posixmodule.c` — after the "all other compilers" block that
     hard-defines `HAVE_SYSTEM`/`FORK`/`EXECV`/`WAIT`/`POPEN` regardless of
     `pyconfig.h`, undefine them again under `TARGET_OS_IPHONE`: the iphoneos SDK
     marks `system()` unavailable and the sandbox forbids the rest.
* **Platform notes:** Android API 24 turns off `HAVE_LANGINFO_H` (bionic declares
  `nl_langinfo` only from API 26); iOS derives its `pyconfig.h` from the macOS one
  (2.7's configure refuses a darwin cross build) and drops process control plus
  `<sys/random.h>`/`getentropy`, but keeps `HAVE_GETGROUPS` because
  `posixmodule.c` defines `MAX_GROUPS` — which its `setgroups` path needs — only
  inside that `#ifdef`. **Windows is out of scope** (decided 2026-09-23, PORT-PLAN §1: the
  targets are macOS arm64 and Android arm64). It is also not buildable as-is:
  upstream supports MSVC + `PC/pyconfig.h`, while the mingw-w64 portability gate
  cross-compiles with MinGW, where `PC/pyconfig.h`'s gnu-win32 branch leaves
  `HAVE_UNISTD_H` unset and `posixmodule.c` / `dynload_win.c` then collide with
  the MinGW headers. So that gate simply builds no `mtpython`, and `port_logic` /
  `port_platform` drop ScriptLib there.
* **License:** PSF License Agreement (`cpython-2.7.18/LICENSE`). Ship-safe; the
  only obligation is keeping the license and a change notice, which this section
  and the patched files' comments serve.

## FreeType 2.13.3 — vendored source, trimmed (not a submodule)

* **Files:** `extension/third_party/freetype-2.13.3/` (~5 MB): the official
  `freetype-2.13.3.tar.xz` (source URL and sha256 in the directory's
  `CMakeLists.txt` header) cut down to `include/`, `src/{base,sfnt,truetype,smooth,raster,psnames,gzip}`,
  `LICENSE.TXT` and `docs/FTL.TXT`.
* **Build:** our own `CMakeLists.txt` (upstream's pulls in optional deps we don't
  want); `mt-config/freetype/config/ftmodule.h` replaces the stock module list with
  TrueType + sfnt + the mono and gray rasterizers. No upstream file is modified.
* **Why:** 40250's `CGraphicFontTexture` / `CGraphicDib` render glyphs with GDI
  (`CreateFontIndirect`, `TextOutW` into a DIB section). `platform/Win32Gdi.cpp`
  implements that GDI subset over FreeType with GDI's cell-height, win-metric and
  gasp rules, so the 40250 font code stays verbatim.
* **License:** FreeType License (`docs/FTL.TXT`, BSD-style with credit clause):
  the shipped product's documentation must credit "Portions of this software are
  copyright © The FreeType Project (www.freetype.org)".

## Rebuilding / fetching

`./build.sh` auto-runs `git submodule update --init --recursive` if any of the
three submodules (godot-cpp, zstd, libsodium-cmake+libsodium) is missing.
miniLZO, Crypto++ and CPython are vendored source and need no fetch.

Homebrew `libsodium` / `zstd` / `lzo` are no longer referenced by the build and
can be uninstalled.