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wasi-sdk-nixos/README.md
Michael Franzl 68fbcfb32e
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2024-05-12 10:09:06 +02:00

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wasm-sdk

A SDK for LLVM C and C++ WebAssembly development based on Nix.

It builds all required dependencies (clang, clang++, wasm-ld, libcxx, compiler-rt, and wasi-libc) and exposes the following environment variables needed to compile to WebAssembly, for example:

WASM_LLVM=/nix/store/akpcpb9ycb98jjbp6dyg1j65vkwqp1lm-wasm-llvm
WASM_LIBCXX_LIB=/nix/store/ll4hi2jkhv8399dhbz6q0qgw97c6hyja-wasm-libcxx/lib
WASM_LIBCXX_INC=/nix/store/ll4hi2jkhv8399dhbz6q0qgw97c6hyja-wasm-libcxx/include/c++/v1
WASM_COMPILER_RT_LIB=/nix/store/59lmk928vly8126zq7mabzc9123hknj2-wasm-compiler-rt/lib/wasi
WASI_LIBC_LIB=/nix/store/qislis4ivwv3l721dbhghax6j4kp3ccb-wasi-libc/lib
WASI_LIBC_INC=/nix/store/71k5vk20275571n0bsij42qdasbxc82b-wasi-libc-dev/include

Goals

  • Lean toolchain leveraging as much as possible from upstream sources.
  • Basic levels of WASI (no threading, no exceptions).

Versions

  • LLVM: 17
  • wasi-libc: 21

Usage

The included derivation produces a single file with exportable environment variables.

Example:

env $(cat $(nix-build -E 'with import <nixpkgs> {}; callPackage ./default.nix {}')) printenv

A flake is also included that exposes the needed variables in the following ways (three ways to choose from, for convenience):

  1. as the paths (attrset type) passthru of the derivation of the default package (to use in other flakes).
  2. as exported environment variables in the default development shell (nix develop).
  3. as text in a file (nix build produces the file ./result).