CSHARP.CLASS.CAST.ARRSTORE : Risky array store (C#)

Summary

The value written into an array cannot be assigned to the type of the elements of the array.

Store operations into arrays might fail at runtime if the type of the elements of the array cannot hold the value written into the array. This situation can arise if an API provides public methods for setting an array and its elements, and those methods have permissive type signatures.

C# checks explicit type downcasts at runtime. If they do not hold, a runtime exception is thrown. This checker verifies that casts will be satisfied at runtime, so that they will never throw an exception.

Properties

WARNING_FILTER += discard class="Risky array store (C#)"

Example

Store operations into arrays might fail at runtime if the type of the elements of the array cannot hold the value written into the array. For instance, the following code will run into an ArrayTypeMismatchException at runtime, since an array of strings cannot hold a System.Object.

public class CheckArrays {
  private final object[] arr;
  private int next;

  public CheckArrays(object[] arr) {
    this.arr = arr;
  }

  public void Add(object o) {
    if (next < arr.Length)
      arr[next++] = o;
  }

  public static void Main(string[] args) {
    CheckArrays ca = new CheckArrays(new string[5]);
    ca.add(new object());            // "Risky array store (C#)" warning issued here
  }
}
  

Resolution

For each classcast warning, verify that all types that will ever reach that program point are assignable to the type used for the cast.

Relevant Configuration File Parameters

The following configuration file parameters affect checks for this warning class.

• REPORT_SIMILAR_WARNINGS
• WARNING_FILTER