@@ -39,6 +39,43 @@ V8 JavaScript 内存占用分析。
39391 . ` __proto__ ` 是原型链。
40402 . ` map ` 就是很多文章都在介绍的 V8 对象的黑魔法 Hidden Class。
4141
42+ ## 使用 V8 进行调试
43+ 44+ V8 的 ` %DebugPrint() ` 函数可以打印出对象的调试信息。这需要手动使用 ` --is_debug=true ` 参数来编译 V8。
45+ 46+ 代码:
47+ 48+ ``` js
49+ let o = {};
50+ % DebugPrint (o);
51+ ```
52+ 53+ 运行:` d8 --allow_natives_syntax heap.js `
54+ 55+ 输出:
56+ 57+ ``` plain
58+ DebugPrint: 0x2604080c60e9: [JS_OBJECT_TYPE]
59+ - map: 0x2604082802d9 <Map(HOLEY_ELEMENTS)> [FastProperties]
60+ - prototype: 0x2604082413c9 <Object map = 0x2604082801c1>
61+ - elements: 0x2604080406e9 <FixedArray[0]> [HOLEY_ELEMENTS]
62+ - properties: 0x2604080406e9 <FixedArray[0]> {}
63+ 0x2604082802d9: [Map]
64+ - type: JS_OBJECT_TYPE
65+ - instance size: 28
66+ - inobject properties: 4
67+ - elements kind: HOLEY_ELEMENTS
68+ - unused property fields: 4
69+ - enum length: invalid
70+ - back pointer: 0x26040804030d <undefined>
71+ - prototype_validity cell: 0x2604081c0451 <Cell value= 1>
72+ - instance descriptors (own) #0: 0x2604080401b5 <DescriptorArray[0]>
73+ - prototype: 0x2604082413c9 <Object map = 0x2604082801c1>
74+ - constructor: 0x2604082413e5 <JSFunction Object (sfi = 0x2604081c5869)>
75+ - dependent code: 0x2604080401ed <Other heap object (WEAK_FIXED_ARRAY_TYPE)>
76+ - construction counter: 0
77+ ```
78+ 4279## License
4380
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