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  1. JDK
  2. JDK-8027227

[asm] generate CONSTANT_InterfaceMethodref for invoke{special/static) of non-abstract methods on ifaces

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        The internal ASM (and the external version) does not generate the correct constant pool entry for invokespecial and invokestatic instructions for non-abstract methods on interfaces.

        Currently ASM will generate a CONSTANT_Methodref entry, rather than a CONSTANT_InterfaceMethodref. This in turn results in incorrect byte code of generated anon classes for lambda expressions and method references, that may result in possible VM-related errors.

        A simple class exercises this aspect:

        import java.util.function.*;

        class A {
          interface I {
              default Supplier<Integer> a() { return () -> 1; }
              default Supplier<Integer> b(int i) { return () -> i; }
              default Supplier<Integer> c(int i) { return () -> m(i); }

              int m(int i);
              
              static Integer d() {
                  return 0;
              }
          }

          static class C implements I {
              public int m(int i) { return i;}
          }

          public static void main(String[] args) {
              I i = new C();

              i.a();
              i.b(1);
              i.c(1);
              I.d();
          }
        }

        Compile and execute with:

        java -Djdk.internal.lambda.dumpProxyClasses=. -cp . A

        then analyze the byte code of the generated proxy classes, for example:

          javap -v -p A\$I\$\$Lambda\$1.class

        Note this currently executes fine, even though the constant pool entry is incorrect (possibly indicating a byte code validation issue with the VM).

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                ksrini Kumar Srinivasan
                psandoz Paul Sandoz
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                  Updated:
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