WASI(X) Libc

This fork of wasi-libc extends libc with the missing functionality needed to build complete and useful applications, in particular it incorporates these additional extensions:

• full support for efficient multithreading including joins, signals and getpid
• pthreads support (now extended from the WASI threads spec)
• full support for sockets (socket, bind, connect, resolve)
  • IPv4, IPv6
  • UDP, TCP
  • Multicast, Anycast
  • RAW sockets
• current directory support (chdir) integrated with the runtime
• setjmp / longjmp support (used extensively in libc ) via asyncify
• process forking (fork and vfork )
• subprocess spawning and waiting (exec , wait )
• TTY support
• asynchronous polling of sockets and files
• pipe and event support (pipe, event )
• DNS resolution support (resolve )

NOTES

• Memory mapping is currently not compatible with threads

WASI(X) Extensions Spec

WASIX is maintained by wasix.org here

WASI(X) intent is to extend the WASI proposal and complete the ABI sufficiently now to build useful and productive applications today - it is not intended as a fork but rather to be a superset on top of WASI. Therefore it maintains full forwards and backwards compatibility with this major version of WASI and stabilizes it for the long term.

WASI(X) Contributions

All contributions are welcome on extending WASI(X) with other extension(s). Just submit your pull request here and we will review via normal GitHub processes.

Long-term Support

WASIX will receive long term support by this community with a guarantee of backwards compatibility on the ABI. Runtime(s) that support this ABI are assured of its stability just as standard libraries and libraries can also count on that same stability to join the dots and make the connections.

Major bug fixes and/or zero day vulnerabilities will be addressed promptly here with careful consideration for resolving issues without compromising the long-term support goal.

Installation

A pre-built sysroot suitable for C/C++ is released in this repository.

To build from source, have a look at the build_cxx_sysroot.yml script and replicate its build steps.

Usage

For building CMake projects, a toolchain file is included in the released sysroot at wasix-sysroot/clang-wasm.cmake_toolchain. In addition to specifying the toolchain:

• wasm-ld is needed for linking. It is usually available in your system's LLVM linker package. It should be in the PATH.
• CMAKE_TOOLCHAIN_FILE and CMAKE_SYSROOT should both be set by you.

The WASIX-specific tests and script in test/wasix can serve as examples for how to set this up.

WASI Libc

WASI Libc is a libc for WebAssembly programs built on top of WASI system calls. It provides a wide array of POSIX-compatible C APIs, including support for standard I/O, file I/O, filesystem manipulation, memory management, time, string, environment variables, program startup, and many other APIs.

WASI Libc is sufficiently stable and usable for many purposes, as most of the POSIX-compatible APIs are stable, though it is continuing to evolve to better align with wasm and WASI. For example, pthread support is still a work in progress.

Usage

The easiest way to get started with this is to use [wasi-sdk], which includes a build of WASI Libc in its sysroot.

Building from source

To build a WASI sysroot from source, obtain a WebAssembly-supporting C compiler (currently this is only clang 8+, though we'd like to support other compilers as well), and then run:

make CC=/path/to/clang/with/wasm/support \
     AR=/path/to/llvm-ar \
     NM=/path/to/llvm-nm

This makes a directory called "sysroot", by default. See the top of the Makefile for customization options.

To use the sysroot, use the --sysroot= option:

/path/to/wasm/supporting/c/compiler --sysroot=/path/to/the/newly/built/sysroot ...

to run the compiler using the newly built sysroot.

Note that Clang packages typically don't include cross-compiled builds of compiler-rt, libcxx, or libcxxabi, for libclang_rt.builtins-wasm32.a, libc++.a, or libc++abi.a, respectively, so they may not be usable without extra setup. This is one of the things [wasi-sdk] simplifies, as it includes cross-compiled builds of compiler-rt, libc++.a, and libc++abi.a.