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  1. JDK
  2. JDK-8185119

Uninitialized const when using multiple threads

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    • b32
    • generic
    • generic

      FULL PRODUCT VERSION :
      java version "1.8.0_152-ea"
      Java(TM) SE Runtime Environment (build 1.8.0_152-ea-b05)
      Java HotSpot(TM) 64-Bit Server VM (build 25.152-b05, mixed mode)

      ADDITIONAL OS VERSION INFORMATION :
      macOS 10.12.5

      A DESCRIPTION OF THE PROBLEM :
      In certain multithreading situations, some local variables are not being initialized properly. This seems to happen when a function declares multiple block-scoped variables that are captured by a closure, and when the function is invoked concurrently from multiple threads.

      When this bug is triggered, the following code may throw a TypeError due to "x" being undefined:

      const x = [1,2,3];
      x.concat(4);

      STEPS TO FOLLOW TO REPRODUCE THE PROBLEM :
      Run the provided script several times, for example:

      for i in {0..10}
      do
        echo Attempt $i
        jjs --language=es6 crash.js
      done

      EXPECTED VERSUS ACTUAL BEHAVIOR :
      EXPECTED -
      The .js script should not generate any output, so the above 'for' loop should display the following:

      Attempt 0
      Attempt 1
      Attempt 2
      Attempt 3
      Attempt 4
      Attempt 5
      Attempt 6
      Attempt 7
      Attempt 8
      Attempt 9
      Attempt 10
      ACTUAL -
      This test case reproduces the issue about 50% of the time.

      ERROR MESSAGES/STACK TRACES THAT OCCUR :
      Attempt 0
      Attempt 1
      Attempt 2
      Attempt 3
      Attempt 4
      Attempt 5
      TypeError: Cannot read property "crash" from undefined
      TypeError: Cannot read property "crash" from undefined
      Attempt 6
      Attempt 7
      TypeError: Cannot read property "crash" from undefined
      TypeError: Cannot read property "crash" from undefined
      Attempt 8
      TypeError: Cannot read property "crash" from undefined
      TypeError: Cannot read property "crash" from undefined
      Attempt 9
      TypeError: Cannot read property "crash" from undefined
      TypeError: Cannot read property "crash" from undefined
      Attempt 10
      TypeError: Cannot read property "crash" from undefined
      TypeError: Cannot read property "crash" from undefined

      REPRODUCIBILITY :
      This bug can be reproduced often.

      ---------- BEGIN SOURCE ----------
      function f() {
         let a;
         const b = {};
         b.crash; // b is sometimes undefined

         function() {
             a, b;
         }
      }

      T = Java.extend(Java.type('java.lang.Thread'), {
          run: function() {
              for (let j = 0; j < 100; j++) {
                  try {
                      f();
                  }
                  catch (e) {
                      print(e);
                      break;
                  }
              }
          }
      });

      new T().start();
      new T().start();

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

      CUSTOMER SUBMITTED WORKAROUND :
      Either of the following will eliminate the issue, in this particular test case:

      - Declare 'a' as 'var'
      - Declare 'b' as 'let' or 'var'


        1. crash.js
          0.4 kB
        2. JI9050140.sh
          0.1 kB

            hannesw Hannes Wallnoefer
            webbuggrp Webbug Group
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              Created:
              Updated:
              Resolved: