Can Function Pointers and Data Pointers Be Interchanged Safely in C/C ?

Interoperability of Function Pointers and Data Pointers in C/C

Despite being pointers and theoretically addressing main memory, function pointers and data pointers in C/C exhibit incompatible behavior in certain scenarios. This incompatibility stems from the underlying architecture and the abstraction provided by the programming language.

Addressing Differences

While many platforms store both code and data in the same memory (Von Neumann architecture), there are also Harvard architectures where these components reside in separate memory spaces. C, as a language designed to be portable across diverse platforms, does not impose exclusive limitations on specific architectures.

Data Storage and Execution

When referring to a data object, a data pointer simply stores its address in memory. The compiler can easily translate this address into the data's actual value during program execution. However, a function pointer stores the address of the function's code itself. This code constitutes a set of instructions that the CPU must execute, rather than a value to be directly manipulated.

Cross-Conversion and Undefined Behavior

Converting a function pointer to a data pointer and vice versa on platforms that adhere to Von Neumann architecture often works due to the coincidence of code and data sharing the same memory. However, it is not guaranteed to work across all architectures, and doing so can lead to undefined behavior.

Example

For instance, on a Harvard architecture, converting a function pointer to a data pointer would result in an address that is invalid for data storage. Conversely, accessing a data pointer as a function pointer could lead to the execution of arbitrary code or a system crash.

The above is the detailed content of Can Function Pointers and Data Pointers Be Interchanged Safely in C/C ?. For more information, please follow other related articles on the PHP Chinese website!