Java字节码子程序-无法加载返回地址

Question

我一直在尝试编写一些Java字节码，并使用Jasmin进行组装。

我试图得到我的头周围的子程序，我不知道为什么我获得以下错误信息时，运行我的程序:

>java -jar jasmin.jar test.j
Generated: test.class
>java test
Exception in thread "main" java.lang.VerifyError: (class: test,
method: main signature: ([Ljava/lang/String;)V)
Cannot load return address from register 0
Could not find the main class: test. Program will exit.

下面是test.j中的字节码:

.class public test
.super java/lang/Object
.method public static main([Ljava/lang/String;)V
.limit stack 6
.limit locals 5
jsr a     ;Jump to subroutine 'a', pushing return address on operand stack
return    ;Exit the program
a:
astore_0  ;Store the return address in variable 0
aload_0   ;Save the address onto the stack as address will be overwritten in 'b'
jsr b     ;Jump to subroutine 'b', pushing return address on operand stack
astore_0  ;Store the address that was on the stack back into variable 0
ret 0     ;Return to just after "jsr a"
b:
astore_0  ;Store return address in variable 0
ret 0     ;Return to address stored in 0 (ie back to just after the jump in 'a')
.end method

我在跳转到单个子例程时没有遇到任何问题，但是当从子例程内跳转到子例程时，似乎有些事情出错了。

任何关于为什么这是失败的见解将非常感激!

Answer 1

您不能将地址类型值加载到任何寄存器中，您只能存储它，然后ret指令可以从那里检索它。

Java Virtual Machine Specification:

• ret
jsr