Module Nullness

Provides predicates for performing nullness analyses.

Nullness analyses are used to identify places in a program where a null pointer exception (NullReferenceException) may be thrown. Example:

void M(string s) {
  if (s != null) {
    ...
  }
  ...
  var i = s.IndexOf('a'); // s may be null
  ...
}

Import path

import semmle.code.csharp.dataflow.Nullness

The default C# QL library.

AlwaysNullExpr	An expression that is always `null`.
Dereference	An expression that dereferences a value. That is, an expression that may result in a `NullReferenceException` if the value is `null`.
MaybeNullExpr	An expression that may be `null`.
NonNullExpr	An expression that is never `null`.
PathNode	An SSA definition, which may be `null`, augmented with at basic block which can be reached without passing through a `null` check.

Provides the query predicates needed to include a graph in a path-problem query for Dereference::is[First]MaybeNull().