[PATCH][asmtools] Fix incorrect handling of some CPX2 constant pool entries by JDIS (original) (raw)

Leonid Kuskov Leonid.Kuskov at Oracle.com
Wed Mar 14 19:04:57 UTC 2018

Hi Maxim,

Thank you for the patch. Indeed it does fix a bug - the fix is correct but it seems to be overloaded with extra code. CX2 class contains enough information to split structures into 2 groups: referencing to CLASS_info (Fieldref, Methodref and InterfaceMethodref) and all others, hence the marker class CPX2_ClassMember is not necessary. There you can just add one method to CX2 as follows: boolean refersClassMember() {     return tag == CONSTANT_FIELD || tag == CONSTANT_METHOD || tag == CONSTANT_INTERFACEMETHOD; } and change only 1 line: -if (cns2.value1 == cd.this_cpx) {

+if ( cns2.value1 == cd.this_cpx && cns2.refersClassMember() ) {

What do you think if I use this shorter fix as your contribution?

Thanks, Leonid

On 3/12/18 16:52, Maxim Degtyarev wrote:

The proposed patch (see attached file jdis-cpx2-bug.diff.txt) address incorrect handling of some constant pool entries represented with CPX2 class by ASMTOOLS JDIS.

JDIS incorrectly assume that field CPX2::value1 is always used to hold index of constant pool entry of type CONSTANTCLASS. This assumption is valid only for entries of type CONSTANTFIELD, CONSTANTMETHOD and CONSTANTINTERFACEMETHOD. For CONSTANTNAMEANDTYPE, CONSTANTMETHODHANDLE, CONSTANTDYNAMIC and CONSTANTINVOKEDYNAMIC this assumption is wrong. As a result asmtools jdis may produce malformed output for valid input. Example: public class Test { // Force class Test entry appear in the constant pool before InvokeDynamic entries. public Class<?> CLASS = Test.class; private static Runnable[] workers = { () -> System.out.println("Test"), () -> System.out.println("Test"), () -> System.out.println("Test"), () -> System.out.println("Test"), () -> System.out.println("Test"), () -> System.out.println("Test"), () -> System.out.println("Test"), () -> System.out.println("Test"), () -> System.out.println("Test"), () -> System.out.println("Test") }; public static void main(String... args) { for(Runnable worker : workers) { worker.run(); } } } One of invokedynamic instructions may be rendered by jdis as invokedynamic InvokeDynamic run:"()Ljava/lang/Runnable;"; instead of invokedynamic InvokeDynamic REFinvokeStatic:java/lang/invoke/LambdaMetafactory.metafactory:"(Ljava/lang/invoke/MethodHandles$Lookup;Ljava/lang/String;Ljava/lang/invoke/MethodType;Ljava/lang/invoke/MethodType;Ljava/lang/invoke/MethodHandle;Ljava/lang/invoke/MethodType;)Ljava/lang/invoke/CallSite;":run:"()Ljava/lang/Runnable;" MethodType "()V", MethodHandle REFinvokeStatic:Test.lambda$static$1:"()V", MethodType "()V";

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