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NPE in BoxedObjectArray.length #798

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scabug opened this issue Apr 23, 2008 · 7 comments
Closed

NPE in BoxedObjectArray.length #798

scabug opened this issue Apr 23, 2008 · 7 comments
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@scabug
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scabug commented Apr 23, 2008

The following code generates cause BoxedObjectArray.length to throw an NPE.

To reproduce run against a large enough directory tree

import java.io.File

object Main {

  def walk(top: File) : Unit = {
      if (top.isDirectory) {
          for (fn <- top.listFiles) walk(fn)
      } else {
          println(top)
      }
  }
  def main(args: Array[String]) = {
    if (args.length == 0) {
        println("No dirname")
        exit(1)
    }
    
    val f = new File(args(0))
    
    walk(f)
  }
}
@scabug
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scabug commented Apr 23, 2008

Imported From: https://issues.scala-lang.org/browse/SI-798?orig=1
Reporter: Yoel Jacobsen (yoeljacobsen)
Attachments:

  • err (created on Feb 14, 2009 10:33:40 AM UTC, 1885 bytes)

@scabug
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scabug commented Apr 29, 2008

@lrytz said:
Can't reproduce it (on a directory tree with millions of entries).

@scabug
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scabug commented Jan 14, 2009

@odersky said:
Milestone next_bugfix deleted

@scabug
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scabug commented Feb 14, 2009

Martin Kneissl (mkneissl) said:
I can reproduce this on my machine:

  • Scala 2.7.3.final
  • java version "1.6.0_10"
    Java(TM) SE Runtime Environment (build 1.6.0_10-b33)
    Java HotSpot(TM) Client VM (build 11.0-b15, mixed mode, sharing)
  • Microsoft Windows XP [Version 5.1.2600]

See also attached stack trace.

@scabug
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scabug commented Feb 14, 2009

Martin Kneissl (mkneissl) said:
Stack trace

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scabug commented Feb 14, 2009

@paulp said:
It's because you're using a null value in a generator (isDirectory == true does not guarantee listFiles != null.) Try it this way:

      def files() = top.listFiles match {
        case null => Nil
        case xs   => xs.toList
      }
      if (top.isDirectory) {
          for (fn <- files) walk(fn)
      } else {
          println(top)
      }

@scabug
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scabug commented Feb 14, 2009

Martin Kneissl (mkneissl) said:
Confirmed. Thanks.

File.listFiles returns null for example when the process has no permissions to list the files of the directory.

@scabug scabug closed this as completed May 18, 2011
@scabug scabug added the build label Apr 6, 2017
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