potential NPE issues in LinkedHashTreeMap.java

[HermioneSW]

Hi,
We are developing a new static analysis tool for catching bugs in Java code. Upon scanning your codebase we find the following:

In LinkedHashTreeMap.java (gson/src/main/java/com/google/gson/internal/LinkedHashTreeMap.java) rebalance function at line 338, we guess right can be a null since it is checked inint rightHeight = right != null ? right.height : 0; at line 343, If it is indeed the case, then Node<K, V> rightLeft = right.left; and Node<K, V> rightRight = right.right; may throw a NPE at line 347 and 348.

Would you please take a look and confirm this is indeed a bug? Thanks a million!!!

[HermioneSW]

Hi, can anyone please take a look and confirm this is a bug? Thanks so much!

[Marcono1234]

If this was an NPE issue, then it would also apply to the local variable left because the usage pattern is the same there.

However, it looks like an NPE cannot occur because:

• leftHeight and rightHight are always >= 0 since Node.height is always > 0 (except if an overflow occurs)

• gson/gson/src/main/java/com/google/gson/internal/LinkedHashTreeMap.java

  Line 346 in 1a9469a

  if (delta == -2) {

  
  Only occurs if rightHeight >= 2, which is only possible if right != null

• gson/gson/src/main/java/com/google/gson/internal/LinkedHashTreeMap.java

  Line 364 in 1a9469a

  } else if (delta == 2) {

  
  Only occurs if leftHeight >= 2, which is only possible if left != null

[Marcono1234]

Probably obsolete because this class was removed by #1992.