caspervonb / wasi-sdk

WASI-enabled WebAssembly C/C++ toolchain

WASI SDK

Quick Start

Download SDK packages here.

About this repository

This repository contains no compiler or library code itself; it uses git submodules to pull in the upstream Clang and LLVM tree, as well as the wasi-libc tree.

The libc portion of this SDK is the wasi-libc.

Upstream Clang and LLVM (from 9.0 onwards) can compile for WASI out of the box, and WebAssembly support is included in them by default. So, all that's done here is to provide builds configured to set the default target and sysroot for convenience.

One could also use a standard Clang installation, build a sysroot from the sources mentioned above, and compile with "--target=wasm32-wasi --sysroot=/path/to/sysroot".

Install

A typical installation from the release binaries might look like the following:

wget https://github.com/WebAssembly/wasi-sdk/releases/download/wasi-sdk-[VERSION]/wasi-sdk-[VERSION]-linux.tar.gz
tar xvf wasi-sdk-[VERSION]-linux.tar.gz

Use

Use the clang installed in the wasi-sdk directory:

CC="[WASI_SDK_PATH]/bin/clang --sysroot=[WASI_SDK_PATH]/share/wasi-sysroot"
$CC foo.c -o foo.wasm

Note: [WASI_SDK_PATH]/share/wasi-sysroot contains the WASI-specific includes/libraries/etc. The --sysroot=... option is not necessary if WASI_SDK_PATH is /opt/wasi-sdk.

Notes for Autoconf

Upstream autoconf now recognizes WASI.

For convenience when building packages that aren't yet updated, updated config.sub and config.guess files are installed at share/misc/config.* in the install directory.

Notable Limitations

This repository does not yet support C++ exceptions. C++ code is supported only with -fno-exceptions for now. Similarly, there is not yet support for setjmp/longjmp. Work on support for exception handling s underway at the language level which will support both of these features.

This repository does not yet support threads. Specifically, WASI does not yet have an API for creating and managing threads yet, and WASI libc does not yet have pthread support.

This repository does not yet support dynamic libraries. While there are some efforts to design a system for dynamic libraries in wasm, it is still in development and not yet generally usable.

There is no support for networking. It is a goal of WASI to support networking in the future though.