getaddrinfo memory leak

Question

I have this code for getting information about IPv4 address:

struct addrinfo hints, *info = NULL;
char addr4[INET_ADDRSTRLEN];

memset(&hints, 0, sizeof(hints));
hints.ai_socktype = SOCK_STREAM;
hints.ai_family = AF_INET;

if (!getaddrinfo(argv[hostPara], NULL, &hints, &info)) {
    inet_ntop(AF_INET, &((const sockaddr_in *)info->ai_addr)->sin_addr, addr4, INET_ADDRSTRLEN);
}
if (info != NULL) {
    freeaddrinfo(info);
}

but when I tested when argv[hostPara] is "www.google.com" I am getting this from valgrind:

==3632== 168 bytes in 1 blocks are still reachable in loss record 1 of 1
==3632==    at 0x4C2B6CD: malloc (in /usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so)
==3632==    by 0x524B5B8: make_request (check_pf.c:249)
==3632==    by 0x524BA53: __check_pf (check_pf.c:342)
==3632==    by 0x5201134: getaddrinfo (getaddrinfo.c:2458)
==3632==    by 0x40186B: main (trace.cc:214)

while if argv[hostPara] is "www.ubuntu.com" there are no memory leaks. What is this magic behavior?

Answer 1

Looking a bit the gblic, it's about object catching in case of ipv6 (look 249 line).

As other members have explained, "still reachable" is not an error itself, but it may hide some buggy situations. In this case it's not a problem, just a warning about something that could hide something nasty.

This warning has also been reported to redhat

The reason of the warning for google and not for ubuntu it's beacause google has ipv6 deployed on its servers and ubuntu not, and then the catching is not performed. You can check it with:

nslookup -q=AAAA www.google.com
nslookup -q=AAAA www.ubuntu.com

Answer 2

This may not be a memory leak (technically it is, but you shouldn't worry about it) sometimes libraries allocate memory the first time a function is called for subsequent calls. you can have valgrind suppress those errors if you want.

From the FAQ:

"still reachable" means your program is probably ok -- it didn't free some memory it could have. This is quite common and often reasonable. Don't use --show-reachable=yes if you don't want to see these reports.