BUG OF THE MONTH | Potential null dereference

V3080 Possible null dereference. Consider inspecting ‘traitFeatureWeightDistribution’. Recommender FeatureParameterDistribution.cs 65

public FeatureParameterDistribution(
         GaussianMatrix traitFeatureWeightDistribution, 
         GaussianArray biasFeatureWeightDistribution)
{
  Debug.Assert(
    (traitFeatureWeightDistribution == null && 
     biasFeatureWeightDistribution == null)
     ||
     traitFeatureWeightDistribution.All(
       w =>    w != null 
            && w.Count == biasFeatureWeightDistribution.Count),
    "The provided distributions should be valid 
     and consistent in the number of features.");
  ....
}

Let’s omit extra strings, having left only the logic of evaluating boolean value to make it easier to sort out:

(traitFeatureWeightDistribution == null && 
 biasFeatureWeightDistribution == null)
||
traitFeatureWeightDistribution.All(
  w =>   w != null 
      && w.Count == biasFeatureWeightDistribution.Count)

Again, the right operand of the operator || is evaluated only if the result of evaluating the left one is false. The left operand can take the false value, including when traitFeatureWeightDistribution == null and biasFeatureWeightDistribution != null. Then the right operand of the operator || will be evaluated, and calling traitFeatureWeightDistribution.All will lead to throwing of ArgumentNullException.

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