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C/C++

Build WebAssembly applications with C/C++ using Emscripten.

Overview​

C/C++ has excellent WebAssembly support through Emscripten. Wasmrun includes built-in support for C/C++ projects without requiring a separate plugin.

Prerequisites​

Quick Start​

# Create project
mkdir my-c-wasm && cd my-c-wasm

# Create hello.c
cat > hello.c << 'EOF'
#include <stdio.h>
#include <emscripten.h>

EMSCRIPTEN_KEEPALIVE
int add(int a, int b) {
    return a + b;
}

EMSCRIPTEN_KEEPALIVE
void greet(const char* name) {
    printf("Hello, %s!\n", name);
}

int main() {
    printf("C WebAssembly module loaded!\n");
    return 0;
}
EOF

# Create Makefile
cat > Makefile << 'EOF'
CC = emcc
CFLAGS = -O2

all:
	$(CC) $(CFLAGS) hello.c -o hello.html

clean:
	rm -f hello.wasm hello.js hello.html
EOF

# Run with Wasmrun
wasmrun run .

Compiling​

Basic Compilation​

emcc hello.c -o hello.html

Optimization​

# Optimize for size
emcc -Os hello.c -o hello.wasm

# Optimize for speed
emcc -O3 hello.c -o hello.wasm

WASI Target​

emcc --target=wasm32-wasi hello.c -o hello.wasm

Example Project​

See examples/c-hello for a complete example.

Best Practices​

  1. Use EMSCRIPTEN_KEEPALIVE to export functions
  2. Enable optimizations for production
  3. Minimize memory usage
  4. Use printf for console output

Additional Resources​