can we pass unsigned char to inet_ntop()

Question

#include <arpa/inet.h>

char buf[INET6_ADDRSTRLEN] = {};
int af = AF_INET;
unsigned char addr[4] = {0x7f, 0x0, 0x0, 0x1};

printf("Address: %s\n", inet_ntop(af, addr, buf, sizeof buf));

Is it valid to pass unsigned char array to inet_ntop() call? The code above works, but the man page says API expects network address structure in the second argument.

Useful ref [INET_NTOP(3) Linux Programmer's Manual](http://man7.org/linux/man-pages/man3/inet_ntop.3.html) — chux - Reinstate Monica, Feb 06 '20 at 16:39
Mark, Any particular reason for not using `struct in_addr addr`? — chux - Reinstate Monica, Feb 06 '20 at 16:40
@chux-ReinstateMonica, it is legacy code, I would not like to make massive changes :) — Mark, Feb 06 '20 at 18:43
If its legacy code and one is using the same legacy compiler, options, OS, you are OK - else I suspect you are [SOL](https://www.urbandictionary.com/define.php?term=shit%20outta%20luck). — chux - Reinstate Monica, Feb 06 '20 at 20:27

score 0 · Answer 1 · answered Feb 06 '20 at 20:42

I see that one implementation uses unsigned long as the one member of struct in_addr addr. If you compile on a system where unsigned long is not 4 bytes - I could foresee trouble. If a system have stricter alignment requirements for struct in_addr than char [], again I could foresee trouble.

In the end, it seems you are looking for assurance that this weak code will be OK going forward. I wish you luck.

can we pass unsigned char to inet_ntop()

1 Answers1