C中字符结尾‘\0’的作用

#include <stdio.h>
#include <assert.h>
#include <stdlib.h>
char *strca(char *dst, const char * src)
{
char *dst_t;
dst_t = (char *)malloc(sizeof(dst) + sizeof(src));
char *start = dst_t;
assert(dst && src);
while(*dst_t = *dst)   //是不会进行越界的，默认‘\0’类似“0”，然后跳出
{
dst_t++; dst++;
}
while(*dst_t = *src)
{
dst_t++; src++;
}
*dst_t = '\0';
return start;
}

int main()
{
char *dst = {"wo ai "};
char *src = {"wo de guo jia !"};
printf("%s\n",strca(dst,src));
return 0;
}