Tree-sitter Wasm standard library

Wasm language modules are compiled without a C standard library. Their external scanners may import the functions listed in imports.txt, and the environment loading the language must provide those functions.

This directory contains a shared implementation of that standard-library subset:

• libc/ contains sources vendored from the wasi-libc revision used by the repository's pinned WASI SDK.
• stdio.c is Tree-sitter's scanner-oriented stdio implementation. It provides in-memory formatting and intentionally implements stream operations as no-ops.
• external_scanner_allocator.c is the resettable allocator used for isolated Wasm language modules.
• external_scanner_stdlib.h is a generated Wasm module containing the vendored libc subset, stdio.c, and the resettable allocator.

When the Tree-sitter Rust library is compiled for wasm32-unknown-unknown, the same vendored libc sources and stdio.c are linked directly into the application. In that environment, allocation is instead provided by Rust's application-selected global allocator.

To refresh the vendored sources and regenerate the embedded module, run:

cargo xtask vendor-wasm-stdlib
cargo xtask build-wasm-stdlib