Program: 109815
Project: 109815
Buggy source:
/** 
 * Checks if any blocks not specified in allowedBlockList exist within the line and if not places the line
 * @param ai One end of the line
 * @param ai1 The other end of the line
 * @param block The block to generate the block circle line with
 * @param meta The metadata to generate the block circle line with
 * @param allowedBlockList The block to exclude from the check
 * @return The coordinates where a block was placed
 */
public ArrayList<int[]> checkAndPlaceBlockLine(int ai[],int ai1[],IBlockState state,List allowedBlockList){
  ArrayList<int[]> places=new ArrayList<int[]>();
  int ai2[]={0,0,0};
  byte byte0=0;
  int j=0;
  for (; byte0 < 3; byte0++) {
    ai2[byte0]=ai1[byte0] - ai[byte0];
    if (Math.abs(ai2[byte0]) > Math.abs(ai2[j])) {
      j=byte0;
    }
  }
  if (ai2[j] == 0) {
    return null;
  }
  byte byte1=otherCoordPairs[j];
  byte byte2=otherCoordPairs[j + 3];
  byte byte3;
  if (ai2[j] > 0) {
    byte3=1;
  }
 else {
    byte3=-1;
  }
  double d=(double)ai2[byte1] / (double)ai2[j];
  double d1=(double)ai2[byte2] / (double)ai2[j];
  int ai3[]={0,0,0};
  int k=0;
  for (int l=ai2[j] + byte3; k != l; k+=byte3) {
    ai3[j]=MathHelper.floor((double)(ai[j] + k) + 0.5D);
    ai3[byte1]=MathHelper.floor((double)ai[byte1] + (double)k * d + 0.5D);
    ai3[byte2]=MathHelper.floor((double)ai[byte2] + (double)k * d1 + 0.5D);
    BlockPos pos=getBlockPos(ai3);
    if (!allowedBlockList.contains(worldObj.getBlockState(pos))) {
      return null;
    }
  }
  for (int l=ai2[j] + byte3; k != l; k+=byte3) {
    ai3[j]=MathHelper.floor((double)(ai[j] + k) + 0.5D);
    ai3[byte1]=MathHelper.floor((double)ai[byte1] + (double)k * d + 0.5D);
    ai3[byte2]=MathHelper.floor((double)ai[byte2] + (double)k * d1 + 0.5D);
    BlockPos pos=getBlockPos(ai3);
    worldObj.setBlockState(pos,state,blockGenNotifyFlag);
    places.add(new int[]{ai3[0],ai3[1],ai3[2]});
  }
  return places;
}

Fixed version (ground truth):
/** 
 * Checks if any blocks not specified in allowedBlockList exist within the line and if not places the line
 * @param ai One end of the line
 * @param ai1 The other end of the line
 * @param block The block to generate the block circle line with
 * @param meta The metadata to generate the block circle line with
 * @param allowedBlockList The block to exclude from the check
 * @return The coordinates where a block was placed
 */
public ArrayList<int[]> checkAndPlaceBlockLine(int ai[],int ai1[],IBlockState state,List allowedBlockList){
  ArrayList<int[]> places=new ArrayList<int[]>();
  int ai2[]={0,0,0};
  byte byte0=0;
  int j=0;
  for (; byte0 < 3; byte0++) {
    ai2[byte0]=ai1[byte0] - ai[byte0];
    if (Math.abs(ai2[byte0]) > Math.abs(ai2[j])) {
      j=byte0;
    }
  }
  if (ai2[j] == 0) {
    return null;
  }
  byte byte1=otherCoordPairs[j];
  byte byte2=otherCoordPairs[j + 3];
  byte byte3;
  if (ai2[j] > 0) {
    byte3=1;
  }
 else {
    byte3=-1;
  }
  double d=(double)ai2[byte1] / (double)ai2[j];
  double d1=(double)ai2[byte2] / (double)ai2[j];
  int ai3[]={0,0,0};
  int k=0;
  for (int l=ai2[j] + byte3; k != l; k+=byte3) {
    ai3[j]=MathHelper.floor((double)(ai[j] + k) + 0.5D);
    ai3[byte1]=MathHelper.floor((double)ai[byte1] + (double)k * d + 0.5D);
    ai3[byte2]=MathHelper.floor((double)ai[byte2] + (double)k * d1 + 0.5D);
    BlockPos pos=TCGenUtils.getBlockPos(ai3);
    if (!allowedBlockList.contains(worldObj.getBlockState(pos))) {
      return null;
    }
  }
  for (int l=ai2[j] + byte3; k != l; k+=byte3) {
    ai3[j]=MathHelper.floor((double)(ai[j] + k) + 0.5D);
    ai3[byte1]=MathHelper.floor((double)ai[byte1] + (double)k * d + 0.5D);
    ai3[byte2]=MathHelper.floor((double)ai[byte2] + (double)k * d1 + 0.5D);
    BlockPos pos=TCGenUtils.getBlockPos(ai3);
    worldObj.setBlockState(pos,state,blockGenNotifyFlag);
    places.add(new int[]{ai3[0],ai3[1],ai3[2]});
  }
  return places;
}