Simple command line arguments spoofer

spoof_cmd.c

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

char * str_concat(char *s1, const char *s2) {
	const size_t a = strlen(s1);
	const size_t b = strlen(s2);
	const size_t size_ab = a + b + 1;

	s1 = realloc(s1, size_ab);

	memcpy(s1 + a, s2, b + 1);

	return s1;
}

int main(int argc, char *argv[]){
	char *str = malloc(0);
	memset(str, 0, sizeof(char));

	str_concat(str, argv[0]);
	str_concat(str, "-real ");

	for(int i = 1; i <= argc - 1; i++) {
		str_concat(str, argv[i]);
		str_concat(str, " ");
	}
	return system(str);
}