Demo WASM and Docker Integration

Learn how to compile a simple C program to WebAssembly (WASM) using a WASI-compatible compiler and then package it into a Docker image with a minimal runtime.

Prerequisites

1. Write a simple C program

Create a file named helloworld.c:

#include <stdio.h>

int main() {
    printf("hello, world\n");
    return 0;
}

2. Compile to a WASM binary

Use the WASI SDK’s Clang to target wasm32-wasi:

clang --target=wasm32-wasi -O3 helloworld.c -o helloworld.wasm

This produces a standalone helloworld.wasm in your working directory.

3. Create the Dockerfile

We’ll build FROM scratch so the final image only contains the WASM binary:

FROM scratch
COPY helloworld.wasm /helloworld.wasm
ENTRYPOINT [ "/helloworld.wasm" ]

Save this as Dockerfile alongside helloworld.wasm.

4. Build the Docker image

Run:

cd path/to/your/project
docker build --platform=wasm/wasm32 -t helloworld-wasm .

5. Run the WASM container

Execute with the WasmEdge runtime support in containerd:

docker run --rm \
  --name wasm-docker-c-program \
  --runtime=io.containerd.wasmedge.v1 \
  helloworld-wasm

You should see:

hello, world

Congratulations! You’ve compiled a C program to WebAssembly and run it inside a Docker container.

Links and References

• Docker’s experimental WASM support
• WASI SDK releases
• WasmEdge runtime