3 WASI Libc is a libc for WebAssembly programs built on top of WASI system calls.
4 It provides a wide array of POSIX-compatible C APIs, including support for
5 standard I/O, file I/O, filesystem manipulation, memory management, time, string,
6 environment variables, program startup, and many other APIs.
8 WASI Libc is sufficiently stable and usable for many purposes, as most of the
9 POSIX-compatible APIs are stable, though it is continuing to evolve to better
10 align with wasm and WASI.
14 The easiest way to get started with this is to use [wasi-sdk], which includes a
15 build of WASI Libc in its sysroot.
17 ## Building from source
19 To build a WASI sysroot from source, obtain a WebAssembly-supporting C compiler
20 (currently this is only clang 8+, though we'd like to support other compilers as well),
24 make WASM_CC=/path/to/clang/with/wasm/support \
25 WASM_AR=/path/to/llvm-ar \
26 WASM_NM=/path/to/llvm-nm
29 This makes a directory called "sysroot", by default. See the top of the Makefile
30 for customization options.
32 To use the sysroot, use the `--sysroot=` option:
35 /path/to/wasm/supporting/c/compiler --sysroot=/path/to/the/newly/built/sysroot ...
38 to run the compiler using the newly built sysroot.
40 Note that Clang packages typically don't include cross-compiled builds of
41 compiler-rt, libcxx, or libcxxabi, for `libclang_rt.builtins-wasm32.a`, libc++.a,
42 or libc++abi.a, respectively, so they may not be usable without
43 extra setup. This is one of the things [wasi-sdk] simplifies, as it includes
44 cross-compiled builds of compiler-rt, libc++.a, and libc++abi.a.
46 [wasi-sdk]: https://github.com/WebAssembly/wasi-sdk