13

以下 C 文件使用 emscripten 编译为 wasm：

int counter = 100;

int count() {
    counter += 1;
    return counter;
}

$ emcc counter.c -o counter.wasm -s WASM=1 -s SIDE_MODULE=1

没有问题。然后我让 webpack 将 wasm 文件（使用wasm-loader）加载为 UInt8Array：

var buffer = new ArrayBuffer(648);
var uint8 = new Uint8Array(buffer);
uint8.set([0,97,115,109,1,0,0,0,0,12,6,100,121,108,105,110,107,144,128,192,2,0,1,150,128,128,128,0,5,96,1,127,0,96,1,127,1,127,96,0,1,127,96,2,127,127,0,96,0,0,2,179,129,128,128,0,10,3,101,110,118,14,68,89,78,65,77,73,67,84,79,80,95,80,84,82,3,127,0,3,101,110,118,13,116,101,109,112,68,111,117,98,108,101,80,116,114,3,127,0,3,101,110,118,5,65,66,79,82,84,3,127,0,3,101,110,118,10,109,101,109,111,114,121,66,97,115,101,3,127,0,3,101,110,118,9,116,97,98,108,101,66,97,115,101,3,127,0,6,103,108,111,98,97,108,3,78,97,78,3,124,0,6,103,108,111,98,97,108,8,73,110,102,105,110,105,116,121,3,124,0,3,101,110,118,18,97,98,111,114,116,83,116,97,99,107,79,118,101,114,102,108,111,119,0,0,3,101,110,118,6,109,101,109,111,114,121,2,0,128,2,3,101,110,118,5,116,97,98,108,101,1,112,0,0,3,137,128,128,128,0,8,1,2,0,3,3,2,4,4,6,242,128,128,128,0,20,127,1,35,0,11,127,1,35,1,11,127,1,35,2,11,127,1,65,0,11,127,1,65,0,11,127,1,65,0,11,127,1,65,0,11,127,1,65,0,11,127,1,65,0,11,124,1,35,5,11,124,1,35,6,11,127,1,65,0,11,127,1,65,0,11,127,1,65,0,11,127,1,65,0,11,124,1,68,0,0,0,0,0,0,0,0,11,127,1,65,0,11,125,1,67,0,0,0,0,11,125,1,67,0,0,0,0,11,127,0,65,0,11,7,184,128,128,128,0,4,6,95,99,111,117,110,116,0,6,18,95,95,112,111,115,116,95,105,110,115,116,97,110,116,105,97,116,101,0,8,11,114,117,110,80,111,115,116,83,101,116,115,0,7,8,95,99,111,117,110,116,101,114,3,26,9,129,128,128,128,0,0,10,190,129,128,128,0,8,173,128,128,128,0,1,1,127,2,64,35,10,33,1,35,10,32,0,106,36,10,35,10,65,15,106,65,112,113,36,10,35,10,35,11,78,4,64,32,0,16,0,11,32,1,15,0,11,0,11,133,128,128,128,0,0,35,10,15,11,134,128,128,128,0,0,32,0,36,10,11,141,128,128,128,0,0,2,64,32,0,36,10,32,1,36,11,11,11,146,128,128,128,0,0,35,12,65,0,70,4,64,32,0,36,12,32,1,36,13,11,11,161,128,128,128,0,1,4,127,2,64,35,10,33,3,35,3,65,0,106,40,2,0,33,0,32,0,65,1,106,33,1,32,1,15,0,11,0,11,133,128,128,128,0,1,1,127,1,11,152,128,128,128,0,0,2,64,35,3,65,16,106,36,10,35,10,65,128,128,192,2,106,36,11,16,7,11,11,11,135,128,128,128,0,1,0,35,3,11,1,100,]);

我的 JS 代码然后调用以下内容：

import Counter from './wasm/counter'
const counter = new Counter();

并且实例化失败并出现以下错误：

LinkError: import object field 'DYNAMICTOP_PTR' is not a Number

wasm-loader 使用以下默认选项（importObject）WebAssembly.Instance(module, importObject)：

{
  'global': {},
  'env': {
    'memory': new Memory({initial: 10, limit: 100}),
    'table': new Table({initial: 0, element: 'anyfunc'})
  }
}

难道我做错了什么 ？如何成功加载 wasm 代码？

编辑： 遵循@Ghillie 的建议，我尝试使用不同的优化标志编译 C 代码：

-O1, -02, -O3,-Os和-Oz throw aLinkError: import object field 'memoryBase' is not a Number这是一个不同的错误，但不能解决问题。

编辑2：

仅添加-O1优化标志不起作用，但允许调试代码有不同的错误消息，因此@Ghillie 和我的答案都为我的问题提供了完整的解决方案。

4

2 回答 2

9

使用除默认值之外的任何优化标志进行编译-O0。例如：

emcc counter.c -O1 -o counter.wasm -s WASM=1 -s SIDE_MODULE=1

此处列出了各种优化标志：

https://kripken.github.io/emscripten-site/docs/optimizing/Optimizing-Code.html

于 2017-06-03T23:16:35.023 回答
8

解决方案似乎是调整importObject使用的WebAssembly.Instance(module, importObject)：

{
  'env': {
    'memoryBase': 0,
    'tableBase': 0,
    'memory': new WebAssembly.Memory({initial: 256}),
    'table': new WebAssembly.Table({initial: 0, element: 'anyfunc'})
  }
}

memoryBase并且tableBase需要并且初始内存值太低（抛出 a LinkedError: Memory of incompatible size）。

我也不得不打电话counter.exports._count()，而不是counter.exports.count()在实例化完成后。

还要感谢@Ghillie，因为-O1确实需要优化标志。

编辑：如果您正在阅读本文并且刚刚开始使用 WebAssembly，我总结了我的第一次体验，以防它有帮助：WebAssembly 101：开发人员的第一步。

于 2017-06-04T10:59:44.200 回答