Exploring the time complexity of strcat() and realloc()

catter.c

#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <time.h>

void measure(char *name, void (*func)(char**,char *,char*,int), char **target, char *initial, char *repeat, int times)
{
	clock_t start, finish;
	start = clock();
	func(target, initial, repeat, times);
	free(*target);
	finish = clock();
	printf("%20s: %10lld\n", name, (long long)(finish - start));
}

void realloc_catter(char **target, char *initial, char *repeat, int times)
{
	*target = malloc(strlen(initial)+1);
	strcpy(*target, initial);
	for (int i = 0; i < times; i++) {
		*target = realloc(*target, strlen(*target) + strlen(repeat) + 1);
		strcat(*target, repeat);
	}
}

void prealloc_catter(char **target, char *initial, char *repeat, int times)
{
	*target = malloc(strlen(initial) + strlen(repeat) * times + 1);
	strcpy(*target, initial);
	for (int i = 0; i < times; i++) {
		strcat(*target, repeat);
	}
}

char *mystrcat(char *target, char *repeat)
{
	for(;;) {
		*target = *repeat;
		if (!*repeat) break;
		target++;
		repeat++;
	}
	return target;
}

void realloc_mycatter(char **target, char *initial, char *repeat, int times)
{
	char *catptr = *target = malloc(strlen(initial)+1);
	strcpy(*target, initial);
	for (int i = 0; i < times; i++) {
		*target = realloc(*target, strlen(*target) + strlen(repeat) + 1);
		catptr = mystrcat(catptr, repeat);
	}
}

void prealloc_mycatter(char **target, char *initial, char *repeat, int times)
{
	char *catptr = *target = malloc(strlen(initial) + strlen(repeat) * times + 1);
	strcpy(*target, initial);
	for (int i = 0; i < times; i++) {
		catptr = mystrcat(catptr, repeat);
	}
}

int main(int argc, char **argv)
{
	if (argc < 4) exit(1);
	char *initial = argv[1];
	char *repeat = argv[2];
	int times = atoi(argv[3]);

	char *target;

	measure("realloc_catter", realloc_catter, &target, initial, repeat, times);

	measure("prealloc_catter", prealloc_catter, &target, initial, repeat, times);

	measure("realloc_mycatter", realloc_mycatter, &target, initial, repeat, times);

	measure("prealloc_mycatter", prealloc_mycatter, &target, initial, repeat, times);

	return 0;
}