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Practical WebAssembly

Generating asm.js Using Emscripten

Explore the process of using Emscripten to compile C++ programs into asm.js, allowing native code execution within JavaScript engines. This lesson guides you through exporting functions, running generated code in browsers, and invoking functions using ccall, helping you understand how to bridge C++ and JavaScript efficiently.

We'll cover the following...

We’ll use Emscripten to port C/C++ programs into asm.js or the WebAssembly binary and then run them inside the JavaScript engine.

Note: Programming languages such as Lua and Python have a C/C++ runtime. With Emscripten, we can port the runtime as a WebAssembly module and execute them inside the JavaScript engine. This makes it easy to run Lua/Python code on the JavaScript engine. Thus, Emscripten and WebAssembly allow the running of native code in the JavaScript engine.

First, let’s create a sum.cpp file:

C++
extern "C" {
    unsigned sum(unsigned a, unsigned b) {
    return a + b;
  }
}

Consider extern "C" (line 1) as something like an export mechanism. All the functions inside are available as an exported function without any changes to their name. Then, we ...