Question

我使用ASM 5.0生成了main.class中的java字节代码，如下所示。

以下是我生成的代码：

javap -c _main.class输出

  public jcalc.lang.CalcObject call();
    Code:
       0: ldc           #9                  // String _main/max
       2: invokestatic  #28                 // Method jcalc/lang/Binding.getBindingFromMain:(Ljava/lang/String;)Ljcalc/lang/Binding;
       5: ldc           #20                 // String A
       7: invokevirtual #38                 // Method jcalc/lang/Binding.refVariable:(Ljava/lang/String;)Ljcalc/lang/CalcObject;
      10: checkcast     #40                 // class jcalc/lang/CalcNumber
      13: ldc           #9                  // String _main/max
      15: invokestatic  #28                 // Method jcalc/lang/Binding.getBindingFromMain:(Ljava/lang/String;)Ljcalc/lang/Binding;
      18: ldc           #22                 // String B
      20: invokevirtual #38                 // Method jcalc/lang/Binding.refVariable:(Ljava/lang/String;)Ljcalc/lang/CalcObject;
      23: checkcast     #40                 // class jcalc/lang/CalcNumber
      26: invokevirtual #44                 // Method jcalc/lang/CalcNumber.operatorGreaterThan:(Ljcalc/lang/CalcNumber;)Ljcalc/lang/CalcBoolean;
      29: dup
      30: astore_3
      31: instanceof    #46                 // class jcalc/lang/CalcBoolean
      34: iconst_0
      35: if_icmpeq     38
      38: aload_3
      39: invokevirtual #52                 // Method jcalc/lang/CalcObject.isNonNull:()I
      42: istore_2
      43: aload_3
      44: if_icmpeq     61
      47: ldc           #9                  // String _main/max
      49: invokestatic  #28                 // Method jcalc/lang/Binding.getBindingFromMain:(Ljava/lang/String;)Ljcalc/lang/Binding;
      52: ldc           #20                 // String A
      54: invokevirtual #38                 // Method jcalc/lang/Binding.refVariable:(Ljava/lang/String;)Ljcalc/lang/CalcObject;
      57: astore_1
      58: goto          72
      61: ldc           #9                  // String _main/max
      63: invokestatic  #28                 // Method jcalc/lang/Binding.getBindingFromMain:(Ljava/lang/String;)Ljcalc/lang/Binding;
      66: ldc           #22                 // String B
      68: invokevirtual #38                 // Method jcalc/lang/Binding.refVariable:(Ljava/lang/String;)Ljcalc/lang/CalcObject;
      71: astore_1
      72: aload_1
      73: areturn

但执行时，

Caused by: java.lang.VerifyError: Expecting a stackmap frame at branch target 38
Exception Details:
  Location:
    _main/max.call()Ljcalc/lang/CalcObject; @35: if_icmpeq
  Reason:
    Expected stackmap frame at this location.
  Bytecode:
    0x0000000: 1209 b800 1c12 14b6 0026 c000 2812 09b8
    0x0000010: 001c 1216 b600 26c0 0028 b600 2c59 4ec1
    0x0000020: 002e 039f 0003 2db6 0034 3d2d 9f00 1112
    0x0000030: 09b8 001c 1214 b600 264c a700 0e12 09b8
    0x0000040: 001c 1216 b600 264c 2bb0               

    at java.lang.Class.forName0(Native Method)
    at java.lang.Class.forName(Class.java:264)
    at jcalc.lang.Binding.defineFunction(Binding.java:87)
    at _main.call(Unknown Source)
    ... 7 more

我知道无论条件是否满足，分支操作都不能改变堆栈大小。

但是在第35行中if_icmpeq操作只是跳转到下一个操作，所以它不会影响堆栈。

我正在使用Java 1.6。任何人都可以详细解释说明验证规则或在哪里找到文件。

非常感谢。

Answer 1

我解决了我的问题。

当加载/存储指令出现TypeCast问题时，ASM无法生成相应的stackmap帧。

所以下次你看到有消息

java.lang.VerifyError：期望分支目标45处的堆栈图帧

检查加载/存储指令的类型。

java.lang.VerifyError：期望使用ASM生成的字节代码发生堆栈图帧

1 个答案: