Is Assigning an Invalid Pointer Address Automatically Undefined Behavior in C?

Is Storing an Invalid Pointer Automatically Undefined Behavior?

When working with pointers in programming, the question arises whether merely storing an invalid memory address in a pointer variable constitutes undefined behavior. Many pointer arithmetic operations hinge on this practice, and pointers themselves are fundamentally integers.

In some situations, the act of even loading an invalid pointer into a register might be considered undefined behavior. This is because certain architectures automatically respond with errors when such an operation is attempted.

The C Draft Standard, section 6.5.6/8 defines the scenario where the pointer operand designates an element of an array object and the result points to an element offset from the starting element, proportional to the integer expression used.

In other cases, the expression points one past the final element of the array object. However, none of these scenarios apply in the case of storing an invalid pointer. The array is not sufficiently large to accommodate a pointer offset adjustment, nor does either the initial or resulting pointer represent an element adjacent to the array's end.

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