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1 | # WASI Libc | |
2 | ||
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. | |
7 | ||
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. For example, pthread support is still a work in | |
11 | progress. | |
12 | ||
13 | ## Usage | |
14 | ||
15 | The easiest way to get started with this is to use [wasi-sdk], which includes a | |
16 | build of WASI Libc in its sysroot. | |
17 | ||
18 | ## Building from source | |
19 | ||
20 | To build a WASI sysroot from source, obtain a WebAssembly-supporting C compiler | |
21 | (currently this is only clang 10+, though we'd like to support other compilers as well), | |
22 | and then run: | |
23 | ||
24 | ```sh | |
25 | make CC=/path/to/clang/with/wasm/support \ | |
26 | AR=/path/to/llvm-ar \ | |
27 | NM=/path/to/llvm-nm | |
28 | ``` | |
29 | ||
30 | This makes a directory called "sysroot", by default. See the top of the Makefile | |
31 | for customization options. | |
32 | ||
33 | To use the sysroot, use the `--sysroot=` option: | |
34 | ||
35 | ```sh | |
36 | /path/to/wasm/supporting/c/compiler --sysroot=/path/to/the/newly/built/sysroot ... | |
37 | ``` | |
38 | ||
39 | to run the compiler using the newly built sysroot. | |
40 | ||
41 | Note that Clang packages typically don't include cross-compiled builds of | |
42 | compiler-rt, libcxx, or libcxxabi, for `libclang_rt.builtins-wasm32.a`, libc++.a, | |
43 | or libc++abi.a, respectively, so they may not be usable without | |
44 | extra setup. This is one of the things [wasi-sdk] simplifies, as it includes | |
45 | cross-compiled builds of compiler-rt, libc++.a, and libc++abi.a. | |
46 | ||
47 | ## Arch Linux AUR package | |
48 | For Arch Linux users, there's an unofficial AUR package tracking this git repo that can be installed under the name [wasi-libc-git]. | |
49 | ||
50 | [wasi-sdk]: https://github.com/WebAssembly/wasi-sdk | |
51 | [wasi-libc-git]: https://aur.archlinux.org/packages/wasi-libc-git/ |