用 c 手撸一个 Java 的 decompiler

失业在家重新学习 c 语言，本来想写一个 arm 的 hook 框架，结果心血来潮，手撸一个 java 的 decompiler

已经支持

• lambda 表达式
• 三元表达式
• 赋值链
• while/do while 循环
• 数据类型推断
• LocalVariableTable signature 还原
• class annotation
• filed annotation
• method annotation
• method 参数 annotation

还在开发

• android dex 支持
• for 循环
• for in 循环
• java code label 支持
• 优化掉 goto 语句
• StringConcatFactory
• varargs 方法支持
• code attribute annotation
• 。。。。。

没有支持的还有一大堆，大体的框子已经写完了，剩下的大部分是体力活了。

收获

• 更恨 c++了
• c 语言不完全掌握，三级指针不敢用，二级指针用的哆哆嗦嗦
• jvm 的运行逻辑算是了解了一知半解
• android dex
• 能写一堆超级复杂的，没有注释谁也看不懂的宏
• 参考了好多 nginx 的代码，写的真好啊！

希望大佬帮忙

哪位大佬有类似编译原理或者编译器开发的交流群或者社区，需要理论指导的时候，十分抓狂。 龙书/虎书/鲸书理论看起来太枯燥。

成果

源码

import java.nio.channels.NotYetBoundException; import java.util.HashMap; import java.util.concurrent.ExecutionException; public class TryCatchNestedInCatch { public static void demo(String name, String ye) { try { int mmm = 1000; } catch (Exception e) { // String e3 = "Exception"; try { int mmm1 = 1000; //demo2(); } catch (NotYetBoundException e100) { String e1 = "NotYetBoundException"; // System.out.println(e1); } catch(Exception e1) { String e2 = "Exception"; // System.out.println(e2); } finally { int mmm2 = 2000; // System.out.println(mmm2); } // System.out.println(e3); } finally { int ccc = 2000; // System.out.println(ccc); } } } 

反编译结果：

import java.nio.channels.NotYetBoundException; import java.util.HashMap; import java.util.concurrent.ExecutionException; public class TryCatchNestedInCatch { public static void demo(String var_0_0, String var_1_1) { exception { // block_id: 1 range: 0 - 35 parent_id: 0 try { // block_id: 2 range: 0 - 4 parent_id: 1 int var_2_2(1) = 1000; goto 74; } catch { // block_id: 3 range: 5 - 30 parent_id: 1 exception { // block_id: 5 range: 6 - 27 parent_id: 3 try { // block_id: 6 range: 6 - 10 parent_id: 5 int var_3_4(1) = 1000; goto 57; } catch { // block_id: 7 range: 11 - 16 parent_id: 5 String var_4_9(1) = "NotYetBoundException"; goto 57; } catch { // block_id: 8 range: 17 - 22 parent_id: 5 String var_4_12(1) = "Exception"; goto 57; } finally { // block_id: 9 range: 23 - 27 parent_id: 5 int var_6_15(1) = 2000; athrow(var_5_14); } } goto 74; } finally { // block_id: 4 range: 31 - 35 parent_id: 1 int var_8_7(1) = 2000; } } } } 

源码：

import java.util.Random; public class Or { public static int a1; public static int a2; public static int a3; public int b1; public int b2; public int b3; public static void main(String[] args) { Random r = new Random(); boolean q = 100 < r.nextInt() || 20 > r.nextInt() && r.nextInt() > 0; int m = 200000; boolean s = r.nextInt() > 20 && r.nextInt() < 100; } public static void st() { Random r = new Random(); boolean q = 100 < r.nextInt() || (Or.a1 = Or.a2 = Or.a3 = 20) > r.nextInt() && r.nextInt() > 0; } public void field() { Random r = new Random(); int[] d = {0, 0, 2, 3}; boolean q = 100 < r.nextInt() || (this.b1 = this.b2 = this.b3 = 20) > r.nextInt() && r.nextInt() > 0; boolean cd = 100 < r.nextInt() || (d[0] = d[2] = this.b3 = 20) > r.nextInt() && r.nextInt() > 0; } public boolean define_or() { int m = 0; int k = 0; int n = 0; int z = 0; Random r = new Random(); boolean dddd = (m = 20) > 100 || ( 30 > ((r.nextInt() > 100 && r.nextInt() != 1000) ? (100 & r.nextInt()) : 20) ? (Or.a1 = this.b1 = m = k = n = 100 > r.nextInt() ? r.nextInt() : 0) : // (100 > r.nextInt() ? r.nextInt() : 0) : (r.nextInt() > 2000 ? 100 : 20) ) < (z = r.nextInt() > 1000 ? 0 : 1); System.out.println(m); System.out.println(k); System.out.println(n); return true; } } 

反编译结果：

import java.util.Random; import java.io.PrintStream; public class Or { public static int a1; public static int a2; public static int a3; public int b1; public int b2; public int b3; public static void main(String[] var_0_0) { Random var_1_1(1) = new Random(); int var_2_6(1) = 100 < var_1_1.nextInt() || 20 > var_1_1.nextInt() && var_1_1.nextInt() > 0 ? 0 : 1; int var_3_3(1) = 200000; int var_4_5(1) = var_1_1.nextInt() > 20 && var_1_1.nextInt() < 100 ? 0 : 1; } public static void st() { Random var_0_0(1) = new Random(); int var_1_2(1) = 100 < var_0_0.nextInt() || Or.a1 = Or.a2 = Or.a3 = 20 > var_0_0.nextInt() && var_0_0.nextInt() > 0 ? 0 : 1; } public void field() { Random var_1_1(1) = new Random(); int[] var_2_2(1) = new int[4]{0, 0, 2, 3}; int var_3_6(1) = 100 < var_1_1.nextInt() || this.b1 = this.b2 = this.b3 = 20 > var_1_1.nextInt() && var_1_1.nextInt() > 0 ? 0 : 1; int var_4_5(1) = 100 < var_1_1.nextInt() || var_2_2[0] = var_2_2[2] = this.b3 = 20 > var_1_1.nextInt() && var_1_1.nextInt() > 0 ? 0 : 1; } public boolean define_or() { int var_1_1(1) = 0; int var_2_2(1) = 0; int var_3_3(1) = 0; int var_4_4(1) = 0; Random var_5_5(1) = new Random(); int var_6_7(1) = var_1_1 = 20 > 100 || 30 > var_5_5.nextInt() > 100 && var_5_5.nextInt() != 1000 ? 20 : 100 & var_5_5.nextInt() ? var_5_5.nextInt() > 2000 ? 20 : 100 : 100 > var_5_5.nextInt() ? Or.a1 = this.b1 = var_1_1 = var_2_2 = var_3_3 = 0 : Or.a1 = this.b1 = var_1_1 = var_2_2 = var_3_3 = var_5_5.nextInt() < var_5_5.nextInt() > 1000 ? var_4_4 = 1 : var_4_4 = 0 ? 0 : 1; System.out.println(var_1_1); System.out.println(var_2_2); System.out.println(var_3_3); return true; } }