Question

The prototype of memset is void *memset(void *s, int c, size_t n);. So why the third parameter is of type size_t ? memset is just an example, I want more general reasons. Thanks in advance.

Answer 1

size_t is the return type of the sizeof operator and is used to describe memory sizes. In the case of memset, it specifies the number of bytes (n) in the memory block (s) that should be set to the given value (c).

The size in bits of size_t varies based on the address space of the target platform. It does not always correlate to the register size. For example, in a segmented memory architecture the sizeof (size_t) can be smaller than the sizeof (void *). Typically, size_t would be 4 bytes on a 32-bit machine, 8 bytes on a 64-bit machine, etc.