Compile C/C++ to Wasm WASI

Now that you have Wasienv installed, let's get our hands dirty!

Wasienv comes with C/C++ support preinstalled, so you just need to run one command to get things running ๐Ÿ™‚

Compiling C files with `wasic`

If you want to compile a simple C example, you can just create the following:

#include <stdio.h>
int main(int argc, char **argv)
if (argc < 2) {
printf("Hello, WASI!\n");
} else {
printf("Hello, %s!\n", argv[1]);
// CPP program to print Fizz Buzz
#include <stdio.h>
int main(void)
int i;
for (i=1; i<=100; i++)
// number divisible by 3 and 5 will
// always be divisible by 15, print
// 'FizzBuzz' in place of the number
if (i%15 == 0)
printf ("FizzBuzz\t");
// number divisible by 3? print 'Fizz'
// in place of the number
else if ((i%3) == 0)
// number divisible by 5, print 'Buzz'
// in place of the number
else if ((i%5) == 0)
else // print the number
printf("%d\t", i);
return 0;

Now that you have this file created, you can execute wasicc

wasicc example.c -o example.wasm

Et voilรก... you will have a new file example.wasm ready to be executed with your favorite WebAssembly runtime!

$ wasmer example.wasm
Hello, WASI!

Did you know?

You can also execute the example.wasm file in your browser or in Node.js using @wasmer/wasi. Check out the examples on how to do it!

Compiling C++ files with `wasic++`

Wasienv also allows you to compile C++ files to Wasm WASI, just run it with wasic++

Using Configure and Make

In some projects, there might be already ./configure files that will configure the system (creating a Makefile normally) to compile a certain project.

If you want to use Wasienv there, you just need to wrap your ./configure call with wasiconfigure!

wasiconfigure ./configure

Wasienv also has a wrapper for Makefiles

wasimake make

Here's an example of a C Project that was compiled to Wasm WASI with wasienv:


Using CMake

Similarly to configure and make, we also have another command that will automatically compile all your projects made with CMake

wasicmake cmake .

Here's an example project: quickjs that was compiled to WebAssembly WASI thanks to Wasienv!

And the file they used for generating the wasm file:

# Install wasienv
curl | sh
mkdir -p build
cd build
wasimake cmake ..
cd ..
make -C build