# crabc libc
crabc is an MIT/Apache-2.0 licensed implementation of the musl C library ABI
and dynamic linker for Linux, written in Rust. It runs unmodified musl-linked
binaries on x86\_64, aarch64 and riscv64 when `libldso.so` is used as the
interpreter, and provides `libc.a` for static linking. crabc is built on the
principle that a libc should be small, easy to audit and safe to maintain;
`unsafe` is confined to syscalls and pointer glue.
crabc tracks musl 1.2.6 and exports its full public symbol surface. It is
validated with musl's own libc-test and a differential harness that runs the
same binaries under musl and crabc, and it is faster than musl on both
x86\_64 and riscv64 (qemu-user) in the microbenchmark suite; process startup
is the one structural exception. See `docs/performance.md`.
Real, unmodified Alpine binaries are tracked in the
[workload matrix](docs/workloads.md): BusyBox, curl, Git, SQLite, nginx,
Redis, CPython, Node.js and PostgreSQL all run under crabc, with a per-project
report and baseline comparison. The [LTP report](docs/ltp.md) records the
`syscalls`, math, memory-management, scheduler, threading and SysV IPC suites
against the same binaries under musl and crabc; the shared suites have
identical failure lists.
Build and cross-compilation instructions are in `AGENTS.md`. Release builds
are size-optimized and stripped, and are produced from `v*` tags; the
workspace is published as the `crabc`, `crabc-libc` and `crabc-ldso` crates.
crabc is licensed under MIT OR Apache-2.0.