Is there a way to force a variable to be stored in the cache in C?

Question

I just had a phone interview where I was asked this question. I am aware of ways to store in register or heap or stack, but cache specifically?

Answer 1

Not in C as a language. In GCC as a compiler - look for __builtin_prefetch.

You might be interested in reading What every programmer should know about memory.

Edit:

Just to clear some confusion - caches are physically separate memories in hardware, but not in software abstraction of the machine. A word in a cache is always associated with address in main memory. This is different from the CPU registers, which are named/addressed separately from the RAM.