Wasmer OS distro packaging notes

• Wasmer is written in Rust. To build Wasmer, where possible, do not directly invoke cargo, but use the supplied Makefile

• Wasmer provides several compilers and the Makefile autodetects when compilers can be compiled and/or installed. Set the environment variables ENABLE_{CRANELIFT,LLVM,SINGLEPASS}=1 to force compiler to be build or to fail trying, e.g:

  $ ENABLE_LLVM=1 make build-wasmer

• make install respects DESTDIR, but prefix must be configured with WASMER_INSTALL_PREFIX, e.g.:

  export WASMER_INSTALL_PREFIX=/usr
  make
  DESTDIR=.../usr make install

• In case you must build/install directly with cargo, make sure to enable at least one compiler feature, like e.g. --features cranelift,

  • Beware that compiling with cargo build --workspace --features … will not enable features on the subcrates in the workspace and result in a headless Wasmer binary that can not compile Wasm files directly.

• If you split the package into several subpackages, beware that the create-exe command of the wasmer CLI requires libwasmer.a to be installed at $WASMER_INSTALL_PREFIX/lib/libwasmer.a. Suggestions for splitting:

  • The wasmer-headless CLI contains a subset of the wasmer's functionalities and should only be packaged when splitting — it must be built explicitly with:

    $ make build-wasmer-headless-minimal install-wasmer-headless-minimal

  • libwasmer, containing libwasmer.so*,

  • libwasmer-dev, containing the header files and a .pc file,

  • libwasmer-static, containing libwasmer.a.

The Wasmer distro packaging story is still in its infancy, so feedback is very welcome.

Miscellaneous: binfmt_misc

Wasmer can be registered as a binfmt interpreter for wasm binaries. An example systemd .service is included here. Please consider statically linking the wasmer binary so that this capability is also available in mount namespaces.