Why I Rewrote json2xml in C—After Making It Fast with Rust

The obvious question is: why write json2xml again in C when the Rust version was already fast? The Rust extension was—and still is—a successful part of the Python json2xml package. It made the common conversion path dramatically faster without changing the Python API. For Python users, that is exactly the right design: install the package, keep the familiar interface, and get native performance where it matters. But I wanted to explore a different product: a small, dependency-free converter that does not require Python at all. Something that can be installed as a single command-line executable, embedded as a C library, or shipped in environments where adding a language runtime is unnecessary overhead. That distinction matters. json2xml-c is not an attempt to prove that C is “better” than Rust. It is an experiment in reducing the whole stack: parse JSON, build the value tree, generate XML, and expose the result through a compact C23 API and a standalone CLI. Once that goal was clear,…