Assertions for Function Parameter Validation

Assertions for Function Parameter Validation

Assertions and toleration of exceptions have some tricky overlaps. Consider the modified version of vector summation with my own “yassert” macro instead:

    float vector_sum_assert_example2(float v[], int n)
    {
        yassert(v != NULL);
        float sum = 0;
        for (int i = 0; i < n; i++) {
                sum += v[i];
        }
        return sum;
    }

This still isn't great in production because it crashes if the assertion fails. Once control flow returns from the failing “yassert” macro, then the rest of the code has “v==NULL” and it will immediately crash with a null-pointer dereference.

Hence, the above code works fine only if your “yassert” assertion macro throws an exception. This requires that you have a robust exception handling mechanism in place above it, which is a significant amount of work.

The alternative is to both assert and handle the error in the same place, which makes for a complex block of code:

   yassert(v != NULL); 
   if (v == NULL) {
            return 0.0;  // Tolerate
    }

Slightly more micro-efficient is to only test once:

    if (v == NULL) {
            yassert(v != NULL); // Always triggers
            return 0.0;  // Tolerate
    }

This is a lot of code that can get repeated all over the place. Various copy-paste coding errors are inevitable.

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