#include <stdlib.h>
#include <string.h>
#include <stdio.h>
 
char * repeat_str(size_t count, const char * src)
{
   size_t len = strlen(src);
   char * result = (char *)malloc(sizeof(char) * len * count);
 
   for(size_t i = 0; i < count; i++)
      strncat(result, src, len);
 
   return result;
}
 
int main(void)
{
	char * result = repeat_str(4, "hello ");
	printf("Result: '%s' (success: %d)", result, (strcmp(result, "hello hello hello ") == 0));
}

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