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  1. JDK
  2. JDK-8192885

Compiler in JDK 10-ea+33 misses to include entry in LineNumberTable for goto instruction of foreach loop

    Details

    • Subcomponent:
    • Introduced In Build:
      b33
    • Introduced In Version:
      10
    • Resolved In Build:
      b35
    • CPU:
      x86_64
    • OS:
      generic
    • Verification:
      Verified

      Description

      FULL PRODUCT VERSION :
      java version "10-ea"
      Java(TM) SE Runtime Environment (build 10-ea+33)
      Java HotSpot(TM) 64-Bit Server VM (build 10-ea+33, mixed mode)


      A DESCRIPTION OF THE PROBLEM :
      Compiler in JDK 10-ea+33 misses to include entry in LineNumberTable for goto instruction of foreach loop. Due to this in case if body of a loop is not executed, debugger will misleadingly show that step after line of foreach loop will be a last line of the body.

      Background information: I'm one of developers of the JaCoCo code coverage tool. This tool relies on line number debug information within class files to provide code coverage highlighting. We have a regression test suite which uncovered the defect reported here.

      And due to this issue in the same case code coverage tool such as JaCoCo will highlight misleadingly last line of a body of foreach loop as partially executed.

      After bisection of http://hg.openjdk.java.net/jdk/jdk/ seems that this regression was introduced by changes for JDK-8175883 :

      $ hg bisect --good jdk-10+30
      $ hg bisect --bad jdk-10+33
      Testing changeset 47839:314ac2e2db63 (143 changesets remaining, ~7 tests)
      1133 files updated, 0 files merged, 320 files removed, 0 files unresolved

      $ hg bisect --good
      Testing changeset 47845:2ac93efc62ed (71 changesets remaining, ~6 tests)
      685 files updated, 0 files merged, 33 files removed, 0 files unresolved

      $ hg bisect --good
      Testing changeset 47862:ebe854b910ff (35 changesets remaining, ~5 tests)
      93 files updated, 0 files merged, 7 files removed, 0 files unresolved

      $ hg bisect --good
      Testing changeset 47871:5ab3961d20dd (18 changesets remaining, ~4 tests)
      51 files updated, 0 files merged, 1 files removed, 0 files unresolved

      $ hg bisect --bad
      Testing changeset 47866:39db80b32b69 (9 changesets remaining, ~3 tests)
      29 files updated, 0 files merged, 4 files removed, 0 files unresolved

      $ hg bisect --bad
      Testing changeset 47864:e29ae57c6421 (4 changesets remaining, ~2 tests)
      17 files updated, 0 files merged, 0 files removed, 0 files unresolved

      $ hg bisect --bad
      Testing changeset 47863:abe64cd683a4 (2 changesets remaining, ~1 tests)
      2 files updated, 0 files merged, 0 files removed, 0 files unresolved

      $ hg bisect --good
      The first bad revision is:
      changeset: 47864:e29ae57c6421
      user: vromero
      date: Mon Nov 20 17:07:21 2017 -0500
      summary: 8175883: bytecode generated for the enhanced for loop may block memory garbage collecting


      STEPS TO FOLLOW TO REPRODUCE THE PROBLEM :
      Compile the provided source file.

      EXPECTED VERSUS ACTUAL BEHAVIOR :
      EXPECTED -
      "line 5" in LineNumberTable as this is the case with JDK 1.8.0_152-b16 , 9.0.1+11 and 10-ea+30 :

        static void example();
          descriptor: ()V
          flags: (0x0008) ACC_STATIC
          Code:
            stack=1, locals=2, args_size=0
               0: invokestatic #2 // Method java/util/Collections.emptyList:()Ljava/util/List;
               3: invokeinterface #3, 1 // InterfaceMethod java/util/List.iterator:()Ljava/util/Iterator;
               8: astore_0
               9: aload_0
              10: invokeinterface #4, 1 // InterfaceMethod java/util/Iterator.hasNext:()Z
              15: ifeq 32
              18: aload_0
              19: invokeinterface #5, 1 // InterfaceMethod java/util/Iterator.next:()Ljava/lang/Object;
              24: astore_1
              25: aload_1
              26: invokestatic #6 // Method nop:(Ljava/lang/Object;)V
              29: goto 9
              32: return
            LineNumberTable:
              line 3: 0
              line 4: 25
              line 5: 29
              line 6: 32
            StackMapTable: number_of_entries = 2
              frame_type = 252 /* append */
                offset_delta = 9
                locals = [ class java/util/Iterator ]
              frame_type = 250 /* chop */
                offset_delta = 22

      ACTUAL -
      No "line 5" in LineNumberTable with JDK 10-ea+33 :

        static void example();
          descriptor: ()V
          flags: (0x0008) ACC_STATIC
          Code:
            stack=1, locals=2, args_size=0
               0: invokestatic #2 // Method java/util/Collections.emptyList:()Ljava/util/List;
               3: invokeinterface #3, 1 // InterfaceMethod java/util/List.iterator:()Ljava/util/Iterator;
               8: astore_0
               9: aload_0
              10: invokeinterface #4, 1 // InterfaceMethod java/util/Iterator.hasNext:()Z
              15: ifeq 32
              18: aload_0
              19: invokeinterface #5, 1 // InterfaceMethod java/util/Iterator.next:()Ljava/lang/Object;
              24: astore_1
              25: aload_1
              26: invokestatic #6 // Method nop:(Ljava/lang/Object;)V
              29: goto 9
              32: aconst_null
              33: astore_0
              34: aconst_null
              35: astore_1
              36: return
            LineNumberTable:
              line 3: 0
              line 4: 25
              line 6: 36
            StackMapTable: number_of_entries = 2
              frame_type = 252 /* append */
                offset_delta = 9
                locals = [ class java/util/Iterator ]
              frame_type = 22 /* same */


      REPRODUCIBILITY :
      This bug can be reproduced always.

      ---------- BEGIN SOURCE ----------
      class Example {
        static void example() {
          for (Object o : java.util.Collections.emptyList()) {
            nop(o);
          }
        }

        static void nop(Object o) {
        }
      }

      ---------- END SOURCE ----------

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              • Assignee:
                vromero Vicente Arturo Romero Zaldivar
                Reporter:
                webbuggrp Webbug Group
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                • Created:
                  Updated:
                  Resolved: