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JDK-6695369 : Regex lookbehind fails to throw exception for non-obvious length quantifiers

Details
Type:
Bug
Submit Date:
2008-04-29
Status:
Open
Updated Date:
2011-02-16
Project Name:
JDK
Resolved Date:
Component:
core-libs
OS:
linux
Sub-Component:
java.util.regex
CPU:
x86
Priority:
P4
Resolution:
Unresolved
Affected Versions:
6
Targeted Versions:

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Description
FULL PRODUCT VERSION :
java version "1.6.0_02"
Java(TM) SE Runtime Environment (build 1.6.0_02-b05)
Java HotSpot(TM) Client VM (build 1.6.0_02-b05, mixed mode, sharing)


ADDITIONAL OS VERSION INFORMATION :
Linux localhost.localdomain 2.6.18-1.2798.fc6 #1 SMP Mon Oct 16 14:54:20 EDT 2006 i686 i686 i386 GNU/Linux


A DESCRIPTION OF THE PROBLEM :
If a regex for lookbehind grouping has multiple non-obvious length quantifiers, matching silently fails without throwing the important exception: Exception in thread "main" java.util.regex.PatternSyntaxException: Look-behind group does not have an obvious maximum length near index [i]nn[/i]


STEPS TO FOLLOW TO REPRODUCE THE PROBLEM :
Write a regex which has a lookbehind group in which multiple non-obvious length quantifiers are used. Do matching or finding on strings using this regex. The regex doesn't throw exception for the wrong quantifiers failing silently instead.


EXPECTED VERSUS ACTUAL BEHAVIOR :
EXPECTED -
The regex throws exception: Exception in thread "main" java.util.regex.PatternSyntaxException: Look-behind group does not have an obvious maximum length near index [i]nn[/i]
ACTUAL -
The regex fails silently. No messages are thrown.

REPRODUCIBILITY :
This bug can be reproduced always.

---------- BEGIN SOURCE ----------
public class LbBug{

  public static void main(String[] args){
    String[] dirs = {
"P:\\ZEN\\NAT\\APPS\\ZMG\\Corel_WordPerfect_12sp3_Install\\Files\\Common\\Borland Shared",
"P:\\ZEN\\NAT\\APPS\\ZMG\\Corel_WordPerfect_12sp3_Install\\Files\\Common\\Borland Shared\\BDE",
"P:\\ZEN\\NAT\\APPS\\ZMG\\Corel_WordPerfect_12sp3_Install\\Files\\Common\\Borland Shared\\BDE\\disp.pak",
"P:\\ZEN\\NAT\\APPS\\ZMG\\Corel_WordPerfect_12sp3_Install\\Files\\Common\\Borland Shared\\BDE\\bdeadmin.cnt",
"P:\\ZEN\\NAT\\APPS\\ZMG\\Corel_WordPerfect_12sp3_Install\\Files\\Common\\Borland Shared\\BDE\\bdeadmin.exe",
"P:\\ZEN\\NAT\\APPS\\ZMG\\Corel_WordPerfect_12sp3_Install\\Files\\Common",
"P:\\ZEN\\NAT\\APPS\\ZMG\\Corel_WordPerfect_12sp3_Install\\Files\\Common\\InstallShield",
"P:\\ZEN\\NAT\\APPS\\ZMG\\Corel_WordPerfect_12sp3_Install\\Files\\Common\\Corel",
};

    // pick only lines that end with a file extension
    String regex = "^.++(?<=\\w+\\.\\w+)$"; // should throw exception ...
    // note: it succeeds in throwing exception: "^.++(?<=\\w\\.\\w+)$"

    for (String s : dirs){
      if (s.matches(regex)){ // ... but fails silently
        System.out.println(s);
      }
    }
  }
}

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

                                    

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