The maintainers of the standard C library for the GCC port to the Atmel AVR microcontroller, which has separate address spaces for code and data, state in Data in Program Space that separate address spaces imply a Harvard architecture. They go on to explain that the C language only has one pointer address space, and thus was not designed for Harvard architecture machines. They then describe the non-standard extensions adopted by GCC for the AVR and the AVR C library to allow access to data stored in instruction (program) memory. They even explain why the const keyword cannot be pressed into service to distinguish data objects to be placed in instruction memory.
