Why Justine Tunney’s Code Makes Me Feel So Inadequate

Cross‑platform executable (Redbean & APE)

Problem: binary portability is limited by OS‑specific executable formats (PE, ELF, Mach‑O) and by differing C standard libraries.

Solution: Justine Tunney created Actually Portable Executable (APE), a format that encapsulates an x86‑64 binary together with a minimal runtime that can be mapped on Windows, Linux, macOS, BSD and even bare‑metal. By linking the program against Cosmopolitan libc (see below), the same APE file runs unchanged on six operating systems. Redbean, a tiny web server, demonstrates this: a single redbean.com file downloaded from https://redbean.dev/ serves HTTP on all supported platforms without recompilation.

Cosmopolitan libc

To make APE useful, the C library had to be portable. Cosmopolitan libc re‑implements the full POSIX and Windows API surface and maps each system call to the native kernel of the host OS. The library is written in C with a small amount of assembly and can be linked statically, eliminating external dependencies. As a result, any program compiled against Cosmopolitan libc inherits the “write‑once‑run‑everywhere” property of APE.

SectorLisp – the smallest Lisp interpreter

SectorLisp is a complete Lisp interpreter that fits in 512 bytes of source code. The binary can be placed in a PC BIOS boot sector and executed directly by the firmware, proving that a functional language runtime can occupy less space than a typical error message.

Blinkenlights – from debugger to x86 emulator

Initially a command‑line debugger that visualized memory writes, Blinkenlights grew into a full‑featured x86 emulator. Its source is under 10 KB and is frequently used as a teaching example for building CPU simulators because the implementation is concise yet faithful to the instruction set.

RoseHub – coordinated security remediation

In 2016 Tunney discovered a critical Java deserialization vulnerability in Apache Commons. Recognizing the widespread impact, she launched the RoseHub project, recruited roughly 50 Google engineers, and coordinated patches for more than 2 600 open‑source repositories that depended on the vulnerable component.

Terminal video playback

A utility decodes MPEG video frames in real time, maps each pixel to an ANSI‑colored character, and streams the result to a standard terminal. The effect is a recognizable moving picture inside a text‑only console.

Llamafile – single‑file large‑language‑model deployment

Combining llama.cpp, Cosmopolitan libc, and APE, Tunney packaged a pretrained LLaMA model into one executable. Users download the file and run it on Windows, Linux or macOS; no Python, Conda, Docker or other runtime is required. The executable retains the cross‑platform capability of APE.

Hand‑written matrix‑multiplication kernels

Using hand‑optimized assembly and CPU‑specific instruction‑set extensions, Tunney produced matrix‑multiplication kernels that deliver 30 %–500 % speed‑up over compiler‑generated code on typical consumer CPUs. The kernels are integrated into the Cosmopolitan toolchain and enable faster local inference for large models without specialized hardware.