It depends on how the compiler memcpy is implemented.

There are generally three types: copy from beginning to end or judge copy (equivalent to memmove).

I wrote a test program after yours.

Charles? message2[60]？ =? ”abcdefghijklmnopqrstuvwxyz”；

Charles? tmp[60]；

int？ Master ()

{

strcpy(tmp，？ Message 2);

printf("tmp=？ \"%s\"\n "，？ tmp)；

memcpy(tmp+4，？ tmp？ +? 16,? 10);

printf("memcpy(tmp+4，？ tmp？ +? 16,? 10); & gt？ tmp？ =? \"%s\"\n "，？ tmp)；

strcpy(tmp，？ Message 2);

memcpy(tmp+6，？ tmp？ +4,? 10);

printf("memcpy(tmp+6，？ tmp？ +4,? 10); & gt？ tmp？ =? \"%s\"\n "，？ tmp)；

strcpy(tmp，？ Message 2);

memcpy(tmp+4，？ tmp？ +6,? 10);

printf("memcpy(tmp+4，？ tmp？ +6,? 10); & gt？ tmp？ =? \"%s\"\n "，？ tmp)；

The test results are as follows

tmp = " abcdefghijklmnopqrstuvwxyz "

memcpy(tmp+4，tmp + 16， 10)； & gttmp = " abcdqrstuvwxyzopqrstuvwxyz "

memcpy(tmp+6，tmp +4， 10)； & gttmp = " abcdefefefijijmnqrstuvwxyz "

memcpy(tmp+4，tmp +6， 10)； & gttmp = " abcdghijklmnopopqrstuvwxyz "

Visible in memcpy(tmp+6, tmp +4,10); When there is superposition. Efef

It shows that my compiler (gcc) used head copy when doing memcpy, that is, copying from the starting address.

Memcpy(tmp+4, tmp +6, 10) if this is correct; If something goes wrong, it is a tail copy.

If nothing goes wrong, then after the judgment, smart copy is equivalent to memmove.