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  1. JDK
  2. JDK-8309811

BytecodePrinter cannot handle unlinked classes

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Details

    • Bug
    • Resolution: Fixed
    • P4
    • 22
    • 22
    • hotspot
    • b04

    Description

      BytecodePrinter always uses Bytes::get_native_u2/u4 to read the index of bytecodes such as the field and invoke bytecodes. However, if this class is not yet linked, the indices should be read using Bytes::get_Java_u2/u4

      (x64 and most supported CPUs are little endian, so the "java" and "native" byte ordering are reversed.)

      https://github.com/openjdk/jdk/blob/16c3d53b1bb60b1c1570731041f564bf13b45098/src/hotspot/share/interpreter/bytecodeTracer.cpp#L66-L67

      This is not a problem for -XX:+TraceBytecodes, which only traces classes that have been linked. However, we'd get bad output when calling Method::print_codes_on() for unlinked classes.

      ==========================

      Test case is the same as in JDK-8309808

      // Output: (debug VM)
      $ java -XX:+UseNewCode -cp ~/tmp BytecodeTracerTest
      [....]
      [ 0] 0x0000000801000a18 class BytecodeTracerTest$Unlinked loader data: 0x00007f3ae0273a40 for instance a 'jdk/internal/loader/ClassLoaders$AppClassLoader'{0x00000007ffce70a8}
      0x00007f3aa8400888 method <init> : ()V
      0x00007f3aa8400880 0 aload_0
      0x00007f3aa8400881 1 invokespecial CP[65792] not in CP <<<<<
      0x00007f3aa8400884 4 return

      0x00007f3aa8400940 method toString : ()Ljava/lang/String;
      0x00007f3aa8400930 0 aload_0
      0x00007f3aa8400931 1 invokevirtual CP[67328] not in CP <<<<<
      0x00007f3aa8400934 4 invokedynamic CP[62719] not in CP <<<<<
      0x00007f3aa8400939 9 areturn

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              iklam Ioi Lam
              iklam Ioi Lam
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                Updated:
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