Building Golem Components in C

Building Golem components having an application manifest is straightforward, just use the golem command line interface:

golem app build

If the project was created using golem app new as recommended, the golem app build command will always work as expected.

The result of the golem app build command is a WebAssembly component file ready to be uploaded to Golem. It does not have to be specified explicitly, as the golem tool will automatically find the correct file when doing for example:

golem component add

Under the hood

Under the hood, building Golem components written in C involves a few steps.

In details, building the component requires the following steps:

Generate the C bindings from the WIT files

$ wit-bindgen c --autodrop-borrows yes ./wit
Generating "example.c"
Generating "example.h"
Generating "example_component_type.o"

Compile the C code

Include all your source files and additionally the generated .c and .o files and use the clang provided as part of the WASM SDK:

$ $WASI_SDK_PATH/bin/clang --sysroot $WASI_SDK_PATH/share/wasi-sysroot  main.c example.c example_component_type.o -o example.module.wasm

Package it into a WASM component

The resulting example.module.wasm is a WebAssembly module, not a component. To be able to use it as a Golem component, use wasm-tools to package the module as a component:

$ wasm-tools component new example.module.wasm -o example.wasm --adapt adapters/tier1/wasi_snapshot_preview1.wasm

Note that the adapters/tier1/wasi_snapshot_preview1.wasm file is placed in the project's directory when using golem new to create the new project.

If needed, it can be manually downloaded from https://github.com/golemcloud/golem-wit/blob/main/adapters/tier1/wasi_snapshot_preview1.wasm (opens in a new tab)

Defining Components Next Steps