FULL PRODUCT VERSION :
java version "1.8.0_121"
Java(TM) SE Runtime Environment (build 1.8.0_121-b13)
Java HotSpot(TM) 64-Bit Server VM (build 25.71-b01-internal-jvmci-0.24, mixed mode)

ADDITIONAL OS VERSION INFORMATION :
Linux stola-ThinkPad 3.16.0-38-generic #52~14.04.1-Ubuntu SMP Fri May 8 09:43:57 UTC 2015 x86_64 x86_64 x86_64 GNU/Linux

A DESCRIPTION OF THE PROBLEM :
Evaluation of /.*((a[^a]+){2})c$/.exec('ababc') results in StringIndexOutOfBoundsException

STEPS TO FOLLOW TO REPRODUCE THE PROBLEM :
1. Start jjs
2. Enter /.*((a[^a]+){2})c$/.exec('ababc')
=> java.lang.StringIndexOutOfBoundsException: String index out of range: -1 is printed into the console

EXPECTED VERSUS ACTUAL BEHAVIOR :
EXPECTED -
Correct result, i.e., ababc, abab, ab printed into the console.
ACTUAL -
java.lang.StringIndexOutOfBoundsException: String index out of range: -1 is printed into the console

ERROR MESSAGES/STACK TRACES THAT OCCUR :
java.lang.StringIndexOutOfBoundsException: String index out of range: -1

REPRODUCIBILITY :
This bug can be reproduced always.

---------- BEGIN SOURCE ----------
/.*((a[^a]+){2})c$/.exec('ababc')
---------- END SOURCE ----------