Why Are Function Pointers and Data Pointers Incompatible in C/C ?

Function Pointers and Data Pointers: Addressing Incompatible Memories

While converting function pointers to data pointers (and vice versa) is surprisingly permitted in C/C , this convenience is not guaranteed across all platforms. This raises the question: why are these pointers inherently incompatible?

The answer lies in the architecture of memory management. In some architectures, such as the Harvard architecture, code and data reside in distinct memory regions. In these systems, function pointers (pointing to instructions) cannot be seamlessly transformed into data pointers (pointing to regular values) because they exist in separate memory domains.

Conversely, in Von Neumann architectures, where code and data coexist in the same memory space, function pointers and data pointers appear compatible. However, C/C does not restrict itself to specific architectures and allows for code that can potentially run on both types of systems.

As a result, to maintain compatibility across all architectures, C/C cannot simply treat function pointers and data pointers as interchangeable addresses into main memory. The potential for incompatibility stems from the diversity of architectural designs that C/C must accommodate.

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