java - By analyzing the bytecode, how can I detect explicit throw statement invocations from within a catch block? -

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i want detect throw statements occur within catch block. instance:

try  {     def(); } catch (ioexception e) {     throw e; } catch (exception e) {     throw new runtimeexception(e); }

first, using eclipse-jdt detect these cases , quite simple, since traverse abstract syntax tree.

now have use framework (bat - bytecode analysis toolkit) deals directly bytecode.

first of all, how catch block represented in bytecode? , how can detect throw statement within it?

each method has exception table maps range of instructions plus , exception type exception handler (it's entry point). not easy translate java code. in general, need examine table , analyse reachable code entry points. of code belongs catch clause. it's matter of identifying athrow instructions.

use javap or other bytecode visualizer play around , understand better. completing code, compiling it, , subjecting javap produces:

public class test extends java.lang.object{ public test();   code:    0:   aload_0    1:   invokespecial   #1; //method java/lang/object."<init>":()v    4:   return  public static void def()   throws java.io.ioexception;   code:    0:   new     #2; //class java/io/ioexception    3:   dup    4:   invokespecial   #3; //method java/io/ioexception."<init>":()v    7:   athrow  public static void main(java.lang.string[])   throws java.io.ioexception;   code:    0:   invokestatic    #4; //method def:()v    3:   goto    19    6:   astore_1    7:   aload_1    8:   athrow    9:   astore_1    10:  new     #6; //class java/lang/runtimeexception    13:  dup    14:  aload_1    15:  invokespecial   #7; //method java/lang/runtimeexception."<init>":(ljava/lang/throwable;)v    18:  athrow    19:  return   exception table:       target type      0     3     6   class java/io/ioexception       0     3     9   class java/lang/exception   }

for method main have 2 exception entry points ("targets"): 6 , 9. following 6, have athrow @ offset 8. following entry point @ 9, have athrow @ offset 18. that's it!


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