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WebAssembly (WASM) for High Performance Apps · 课时

使用 Emscripten 将 C/C++ 编译为 WASM

设置开发环境，并使用 Emscripten 工具链将您的第一个 C/C++ 程序编译为 WebAssembly 模块

使用 Emscripten 将 C/C++ 编译为 WASM 是 CoddyKit 上的免费 WebAssembly (WASM) for High Performance Apps 课时。 这是第 1 节课，共 4 节。 你可以在下方免费阅读本课时的完整内容 — 然后在浏览器中使用内置代码编辑器和全天候 AI 导师进行实践。 这是 WebAssembly (WASM) for High Performance Apps 学习路径的一部分，你的进度在网页和 CoddyKit 应用中同步。 WebAssembly (WASM) for High Performance Apps 课程共包含 4 节课。

本课时的部分内容尚未翻译，以英文显示。

Meet Emscripten!

Welcome! Today, we'll learn to compile C/C++ code into WebAssembly (WASM). The key tool for this is Emscripten.

Emscripten is a complete toolchain that takes C/C++ code and compiles it into WASM, along with "glue" JavaScript code to help run it in a web browser or Node.js environment.

Bridging C/C++ to WASM

Why Emscripten? Browsers don't understand C/C++ directly. Emscripten acts as a powerful translator.

  • It compiles your C/C++ into the efficient WASM binary format.
  • It generates JavaScript "glue" code to load the WASM module and interact with it from JavaScript.
  • It handles C/C++ standard library functions (like printf) by providing JavaScript equivalents.

Setting Up Emscripten

Setting up Emscripten involves downloading the Emscripten SDK (emsdk). This SDK contains everything you need: the emcc compiler, Node.js, Python, and other utilities.

Typically, you'd run commands like:

  • git clone https://github.com/emscripten-core/emsdk.git
  • cd emsdk
  • ./emsdk install latest
  • ./emsdk activate latest

This prepares your environment to use emcc.

A Simple C Function

Let's start with a very simple C program. This program defines a function add and calls it from main. We'll compile this into WASM.

 #include <stdio.h>

// A simple C function to add two numbers
int add(int a, int b) {
    return a + b;
}

int main() {
    int result = add(5, 7);
    printf("Result of add(5, 7): %d\n", result);
    return 0;
}

The `emcc` Command

The heart of Emscripten is the emcc compiler. It's a drop-in replacement for gcc or clang that knows how to target WebAssembly.

You'll use emcc just like you would a standard C/C++ compiler, but with specific flags to control the WASM output.

Compiling Our C Code

Now, let's compile our add.c file. We'll tell emcc to output a JavaScript file that includes the compiled WASM module.

The command -o add.js tells Emscripten to create add.js (the glue code) and add.wasm (the binary module).

emcc add.c -o add.js -s EXPORTED_FUNCTIONS="['_add']" -s EXPORT_ES6=1

The Generated Files

After running the emcc command, you'll find two main files:

  • add.wasm: This is the actual WebAssembly binary module. It contains the compiled add function in a highly optimized, compact format.
  • add.js: This is the JavaScript "glue" code. It's responsible for loading add.wasm, setting up the WASM environment, and providing an interface to call functions exported from the WASM module.

What the Glue Does

The generated JavaScript glue code (e.g., add.js) is crucial. It handles:

  • Fetching and instantiating the .wasm file.
  • Setting up the WASM module's memory.
  • Converting JavaScript types to WASM types and vice-versa.
  • Providing an object (often named Module) to interact with the WASM module's exported functions.

This allows you to seamlessly call your C functions from JavaScript.

Optimizing Your WASM

Emscripten allows you to optimize your WASM output for size and speed. This is crucial for web performance.

You can use optimization flags similar to gcc:

  • -O0: No optimizations (fastest compile time).
  • -O1, -O2: Standard optimizations.
  • -O3: Aggressive optimizations (slower compile, smaller/faster code).
  • -Os: Optimize for size.
  • -Oz: Optimize aggressively for smallest size.

For production, emcc -O3 or emcc -Oz are common choices.

Quick Check: Emscripten

You've learned about Emscripten and its role. Let's test your understanding!

Recap: Compiling C/C++

In this lesson, you've taken your first step into WebAssembly with C/C++!

  • We introduced Emscripten as the toolchain for compiling C/C++ to WASM.
  • You saw how emcc compiles C code into .wasm and .js glue files.
  • We discussed the purpose of both the WASM binary and the JavaScript glue code.
  • You learned about basic optimization flags for emcc.

Next, we'll dive into how to load and run these WASM modules in a web browser using JavaScript!

常见问题解答

「使用 Emscripten 将 C/C++ 编译为 WASM」课时是免费的吗？

是的 — 「使用 Emscripten 将 C/C++ 编译为 WASM」的完整文本可在网页上免费阅读。要进行交互式练习（内置代码编辑器和全天候 AI 导师）并解锁 WebAssembly (WASM) for High Performance Apps 课程的其余内容，请升级到 CoddyKit PRO。 WebAssembly (WASM) for High Performance Apps 课程共包含 4 节课。

「使用 Emscripten 将 C/C++ 编译为 WASM」这节课中我会学到什么？

设置开发环境，并使用 Emscripten 工具链将您的第一个 C/C++ 程序编译为 WebAssembly 模块 你通过在浏览器中直接运行的动手代码来练习 WebAssembly (WASM) for High Performance Apps，全天候 AI 导师会在你学习这节课的过程中回答你的问题。

学习 WebAssembly (WASM) for High Performance Apps 需要有经验吗？

无需任何先前经验。CoddyKit 上的 WebAssembly (WASM) for High Performance Apps 课程适合初学者到高级学习者，你可以从这里开始或从头开始，按照自己的节奏学习。 这是第 1 节课，共 4 节。

「使用 Emscripten 将 C/C++ 编译为 WASM」课时需要多长时间？

大多数 CoddyKit 课程大约需要 5–10 分钟。每节课都很精短且互动，所以你能稳步进步，并在网页和应用中从离开的地方继续。

我能在这节 WebAssembly (WASM) for High Performance Apps 课中编写并运行代码吗？

能。每节 WebAssembly (WASM) for High Performance Apps 课都包含内置代码编辑器，你可以在浏览器中直接编写并运行真实代码，并获得即时 AI 反馈 — 无需本地设置。

此课程中的所有课时

  1. 使用 Emscripten 将 C/C++ 编译为 WASM
  2. 在 JavaScript 中加载并运行 WASM
  3. 基本数据交换：原始类型
  4. 从 C/C++ 调用 JavaScript 函数
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