Hi there I've been using Nim's foreign function interface to interface with C
libs on linux with much joy for some time. I haven't run into any issues until
now. I have a utmp object defined in <utmp.h>. I have a simple app that just
prints out currently logged in users - similar output to say what the w command
does.
type
utmpx* = object
ut_type*:ut_type # Type of record
ut_pid*:cint # PID of login process
ut_line*:array[UT_LINESIZE,char] # Device name of tty - "/dev/"
ut_id*:array[4,char] # Terminal name suffix or
inittab(5) ID
ut_user*:array[UT_NAMESIZE,char] # Username
ut_host*:array[UT_HOSTSIZE,char] # Hostname for remote login, or
kernel version for run-level messages
ut_session*:cint # Session ID (getsid(2))
ut_tv*:tv # Time entry was made */
ut_addr_v6*:array[4, uint32] # Internet address of remote host;
IPv4 address uses just ut_addr_v6[0]
Run
The issue appears when trying to read the ip address. The C equivalent is like
so
const char *addr_string;
char buffer[INET6_ADDRSTRLEN];
if (ut->ut_addr_v6[1] || ut->ut_addr_v6[2] || ut->ut_addr_v6[3])
addr_string = inet_ntop(AF_INET6, &(ut->ut_addr_v6), buffer,
sizeof(buffer));
else
addr_string = inet_ntop(AF_INET, &(ut->ut_addr_v6), buffer,
sizeof(buffer));
printf("ip is %s\n",addr_string);
Run
The nim version returns the wrong IP addresses - struggling to figure out why
the difference?
var
buff: array[0..255, char]
ip:cstring
if ut.ut_addr_v6[1] == 0 and ut.ut_addr_v6[2] == 0 and ut.ut_addr_v6[3] ==
0:
let ip = inet_ntop(AF_INET,ut.ut_addr_v6.addr[0].addr, buff[0].addr,
buff.sizeof.int32)
else:
let ip = inet_ntop(AF_INET6, ut.ut_addr_v6.addr[0].addr, buff[0].addr,
buff.sizeof.int32)
Run
