How to use the command wasm2c (with examples)

Wasm2c is a command-line tool that allows you to convert a file from the WebAssembly binary format to a C source file and header. This tool is part of the wabt (WebAssembly Binary Toolkit) project and provides a convenient way to work with WebAssembly modules in C.

Use case 1: Convert a file to a C source file and header and display it to the console

Code:

wasm2c file.wasm

Motivation: This use case is helpful when you want to inspect the generated C code and header directly on the console. It allows you to quickly assess the C code representation of a WebAssembly module without generating additional files.

Explanation:

• wasm2c: The command used to convert a file from the WebAssembly binary format to a C source file and header.
• file.wasm: The input file in the WebAssembly binary format.

Example output:

/* Generated by wasm2c */

#include <stdint.h>

extern int32_t sum(int32_t, int32_t);

int main() {
    int32_t a = 10;
    int32_t b = 20;
    int32_t result = sum(a, b);
    return result;
}

Use case 2: Write the output to a given file

Code:

wasm2c file.wasm -o file.c

Motivation: This use case is useful when you want to write the generated C source file and header to specific files. It allows you to have the C code representation of a WebAssembly module saved for further use or modification.

Explanation:

• wasm2c: The command used to convert a file from the WebAssembly binary format to a C source file and header.
• file.wasm: The input file in the WebAssembly binary format.
• -o file.c: The -o flag followed by the desired output file name. In this example, the C source file will be saved as file.c, and file.h will also be generated alongside.

Example output: file.c:

/* Generated by wasm2c */

#include <stdint.h>

extern int32_t sum(int32_t, int32_t);

int main() {
    int32_t a = 10;
    int32_t b = 20;
    int32_t result = sum(a, b);
    return result;
}

file.h:

/* Generated by wasm2c */

#include <stdint.h>

extern int32_t sum(int32_t, int32_t);

Conclusion:

The wasm2c command provides a straightforward way to convert WebAssembly binary files to C source files and headers. With this tool, you can easily work with WebAssembly modules in a C programming environment, enabling you to inspect, modify, and even enhance the functionalities of existing WebAssembly modules. Whether you want to quickly view the C code representation or save it to files for future use, wasm2c is a powerful tool to have in your WebAssembly toolkit.