A DESCRIPTION OF THE PROBLEM :
A good description of this bug can be found at
https://github.com/ItzSomebody/StopDecompilingMyJava/blob/master/decompiler-tool-bugs/Entry-011/Entry.md

Copied here:

See: https://twitter.com/LeeAtBenf/status/1136035843955732486

Also see: https://github.com/ItzSomebody/openjdk-jdk8u/blob/e87709def542f064a7ab9fa75542230e40876310/hotspot/src/share/vm/classfile/classFileParser.cpp#L2137

Utilizes differences in the pre-Java 1 classfile format (major version 45, minor version 2 and below) and the modern Java classfile format.

Regularly, Java's Method Code Attribute obeys the following:

Code_attribute {
    u2 attribute_name_index;
    u4 attribute_length;
    u2 max_stack;
    u2 max_locals;
    u4 code_length;
    u1 code[code_length];
    u2 exception_table_length;
    { u2 start_pc;
        u2 end_pc;
        u2 handler_pc;
        u2 catch_type;
    } exception_table[exception_table_length];
    u2 attributes_count;
    attribute_info attributes[attributes_count];
}

However, pre-Java 1 classfiles do not. In pre-Java 1, the max_stack, max_locals, and code_length use half size data types. This means pre-Java 1's classfiles follow this format:

Code_attribute {
    u2 attribute_name_index;
    u2 attribute_length;
    u1 max_stack; // uint8_t vs. uint16_t
    u1 max_locals; // uint8_t vs. uint16_t
    u2 code_length; // uint16_t vs. uint32_t
    u1 code[code_length];
    u2 exception_table_length;
    { u2 start_pc;
        u2 end_pc;
        u2 handler_pc;
        u2 catch_type;
    } exception_table[exception_table_length];
    u2 attributes_count;
    attribute_info attributes[attributes_count];
}

STEPS TO FOLLOW TO REPRODUCE THE PROBLEM :
1. Download proof of concept jar file: https://github.com/ItzSomebody/StopDecompilingMyJava/blob/master/decompiler-tool-bugs/Entry-011/PoC.jar

2. execute java -jar PoC.jar, code gets executed without any problem

3. execute javap -cp PoC.jar Test or javap -c -v -p -cp PoC.jar, error gets shown

EXPECTED VERSUS ACTUAL BEHAVIOR :
EXPECTED -
disassembled bytecode
ACTUAL -
Error of javap -cp PoC.jar Test:

Error: Unexpected or invalid value for Code attribute


Error of javap -v -p -c -cp PoC.jar Test:

Error: Unexpected or invalid value for Code attribute
Error: java.lang.reflect.InvocationTargetException
      Code: length = 0x11
       0A 05 00 09 B2 00 07 12 01 B6 00 08 B1 00 00 00
       00
}

---------- BEGIN SOURCE ----------
Proof of concept jar file: https://github.com/ItzSomebody/StopDecompilingMyJava/blob/master/decompiler-tool-bugs/Entry-011/PoC.jar
---------- END SOURCE ----------

FREQUENCY : always