Program: 9467
Project: 9467
Buggy source:
public static String makeLocationContext(ICompilationUnit compilationUnit,IProblem problem){
  int startPosition=problem.getSourceStart();
  int endPosition=problem.getSourceEnd();
  if ((startPosition > endPosition) || ((startPosition <= 0) && (endPosition <= 0)))   return "String_Node_Str";
  final char SPACE='\u0020';
  final char MARK='^';
  final char TAB='\t';
  char[] source=compilationUnit.getContents();
  int begin=startPosition >= source.length ? source.length - 1 : startPosition;
  int relativeStart=0;
  int end=endPosition >= source.length ? source.length - 1 : endPosition;
  int relativeEnd=0;
  label:   for (relativeStart=0; ; relativeStart++) {
    if (begin == 0)     break label;
    if ((source[begin - 1] == '\n') || (source[begin - 1] == '\r'))     break label;
    begin--;
  }
  label:   for (relativeEnd=0; ; relativeEnd++) {
    if ((end + 1) >= source.length)     break label;
    if ((source[end + 1] == '\r') || (source[end + 1] == '\n')) {
      break label;
    }
    end++;
  }
  char[] extract=new char[end - begin + 1];
  System.arraycopy(source,begin,extract,0,extract.length);
  char c;
  int trimLeftIndex=0;
  while (((c=extract[trimLeftIndex++]) == TAB) || (c == SPACE)) {
  }
  ;
  System.arraycopy(extract,trimLeftIndex - 1,extract=new char[extract.length - trimLeftIndex + 1],0,extract.length);
  relativeStart-=trimLeftIndex;
  int pos=0;
  char[] underneath=new char[extract.length];
  for (int i=0; i <= relativeStart; i++) {
    if (extract[i] == TAB) {
      underneath[pos++]=TAB;
    }
 else {
      underneath[pos++]=SPACE;
    }
  }
  for (int i=startPosition + trimLeftIndex; i <= (endPosition >= source.length ? source.length - 1 : endPosition); i++)   underneath[pos++]=MARK;
  System.arraycopy(underneath,0,underneath=new char[pos],0,pos);
  return new String(extract) + "String_Node_Str" + new String(underneath);
}

Fixed version (ground truth):
public static String makeLocationContext(ICompilationUnit compilationUnit,IProblem problem){
  int startPosition=problem.getSourceStart();
  int endPosition=problem.getSourceEnd();
  if ((startPosition > endPosition) || ((startPosition <= 0) && (endPosition <= 0)) || compilationUnit == null)   return "String_Node_Str";
  final char SPACE='\u0020';
  final char MARK='^';
  final char TAB='\t';
  char[] source=compilationUnit.getContents();
  int begin=startPosition >= source.length ? source.length - 1 : startPosition;
  int relativeStart=0;
  int end=endPosition >= source.length ? source.length - 1 : endPosition;
  int relativeEnd=0;
  label:   for (relativeStart=0; ; relativeStart++) {
    if (begin == 0)     break label;
    if ((source[begin - 1] == '\n') || (source[begin - 1] == '\r'))     break label;
    begin--;
  }
  label:   for (relativeEnd=0; ; relativeEnd++) {
    if ((end + 1) >= source.length)     break label;
    if ((source[end + 1] == '\r') || (source[end + 1] == '\n')) {
      break label;
    }
    end++;
  }
  char[] extract=new char[end - begin + 1];
  System.arraycopy(source,begin,extract,0,extract.length);
  char c;
  int trimLeftIndex=0;
  while (((c=extract[trimLeftIndex++]) == TAB) || (c == SPACE)) {
  }
  ;
  System.arraycopy(extract,trimLeftIndex - 1,extract=new char[extract.length - trimLeftIndex + 1],0,extract.length);
  relativeStart-=trimLeftIndex;
  int pos=0;
  char[] underneath=new char[extract.length];
  for (int i=0; i <= relativeStart; i++) {
    if (extract[i] == TAB) {
      underneath[pos++]=TAB;
    }
 else {
      underneath[pos++]=SPACE;
    }
  }
  for (int i=startPosition + trimLeftIndex; i <= (endPosition >= source.length ? source.length - 1 : endPosition); i++)   underneath[pos++]=MARK;
  System.arraycopy(underneath,0,underneath=new char[pos],0,pos);
  return new String(extract) + "String_Node_Str" + new String(underneath);
}