The definition of the c library function memmove is like the following:
void* memmove(void *s1, const void *s2, size_t n)
{
char *sc1;
const char *sc2;
sc1 = s1;
sc2 = s2;
...
}
I'm wondering why do we need to use void* and const void* as the parameters' type. Why not directly char* and const char*?
int test_case[] = {1, 2, 3, 4, 5, 6, 7, 8, 10};
memmove(test_case+4, test_case+2, sizeof(int)*4);
Output: test_case = {1, 2, 3, 4, 3, 4, 5, 6, 10}
If char* and const char* are used, then we have to always cast to char* when invoking memmove on other types.
By using void* and const void*, we are able to write shorter code, and the casting has no performance overhead.
void * is the generic pointer type. memmove is supposed to manipulate memory regardless of what type of objects are in the memory.
Similarly for memcpy. Compare it with strcpy which uses char * parameters because it's supposed to manipulate strings.