pxx

Pxx is a Pascal and C compiler. Written in pascal, it self-hosts and cross-compiles — x86-64, i386, ARM (32 and 64), riscv, xtensa, and the ESP32.

Flagship: the ESP32, in Pascal and in Python. Pascal and nilpy compile to native code for the ESP32-S3, ESP32-C3 and classic ESP32 as an ESP-IDF component, with no interpreter on the chip; the examples have run on physical boards of all three. See ESP32 and getting started on the ESP32.

Beta 0.1 "Blaise" is out. Download it from GitHub (x86-64 Linux; source and prebuilt binaries in one tarball): ./install.sh --yes, then ./pxx hello.py hello. Plain Python in, a static native binary out. Release notes.

Beta 0.1 "Blaise" at a glance

On the chip, not just the emulator. On a physical ESP32-C3 and ESP32-S3 (2026-09-28, compiler built from tree cdd6fd3c1f), every example passed: 12 plus a Wi-Fi access point on the C3, 16 on the S3. A Python program importing a Pascal unit, and a Pascal program calling C, both ran on a real C3. Over real Wi-Fi, 300 HTTP fetches on the S3 and 300 MQTT sessions on each chip ran with 0 errors and no heap growth, beside deliberate-leak controls that would have shown one.
Memory leaks were release blockers. Before pin v441, 164 automated leak checks, 49 Pascal shapes on seven targets and real programs were re-run; five compiler leaks were found and fixed. More found since are fixed in v442, v446 and v447. Still open in v447: del name in Nil Python frees nothing until the function returns, and reference cycles are never freed.
Cross-platform. Linux on x86-64, i386, aarch64, arm32 and riscv32, plus wasm32. Threads give each thread its own threadvar and C __thread on x86-64, i386, aarch64 and arm32 (pin v446).
C. c-testsuite 220 of 220 on x86-64 (pins v441 and v445). SQLite, Lua, zlib, QuickJS and BusyBox build unmodified; BusyBox links with no libc.
Known issues: Nil Python is best effort, not CPython; C long double is 8 bytes; bare-metal ESP images run under QEMU only; https:// through OpenSSL is x86-64 only in v447. The full list is Known issues.

Beta 0.1 "Blaise" (pin v452, September 2026). Development is ongoing: work continues on master, and fixes made since reach the next release. Sponsors are welcome: open an issue titled "Sponsorship" at https://github.com/yoctobyte/pxx/issues.

Features

Pascal, C and Python frontends — nilpy is mainline, a peer of the other two.
Self-hosting; highly FPC- and C99-compatible.
Wrapper-free C import — uses / import a C header directly, no bindings.
Auto-typing — declare a variable auto, the compiler infers the type.
libc-free, syscall-only static binaries.
Cross-compiles to six CPU targets, including the ESP32 through ESP-IDF.
Managed memory (ansistring, dynamic arrays), OOP, coroutines / async.

Design

From scratch — not a fork. Targets compatibility, verified against gcc / fpc / cpython as oracles.
No GNU userland, no libc. Both the compiler and the binaries it emits talk straight to the Linux kernel through syscalls. Building pxx needs only make, and only for the tests.
One shared IR under every frontend and target.
Compiles itself in plain linear pascal — no OOP — so fewer features can miscompile the compiler.

Limitations

Not fully optimized, and -O3 is experimental. How much slower depends on the program: a sudoku solver takes 2.2x as long as FPC's -O2 build (pin v447), and the one Python program measured against CPython, a 3D simulator, ran at 1.89 frames per second against CPython's 37.1 (pin v416).
A beta with a large backlog; expect rough edges. Development is ongoing.