Remove call to obsolete gethostbyname, using getaddrinfo

[serge-sans-paille]

Summary

From the man page:

The gethostbyname*() and gethostbyaddr*() functions are obsolete.
Applications should use getaddrinfo(3) and getnameinfo(3) instead.

That's what I did, using the canonical name as a relevant entry, which looks like the closer match to the original call.

[labath]

Sounds like a good idea, particularly as gethostbyname is not thread safe. It seems getaddrinfo is already used in lldb, so it should be supported by all OSs that we care about.

[davezarzycki]

This code is trying too hard and failing. Either the result of gethostname() is canonical or it is not. If it is not, then trying to canonicalize it is – for various reasons – a lost cause. For example, a given machine might have multiple network interfaces with multiple addresses per interface, each with a different canonical name. Separably, the result of HostInfoPosix::GetHostname() and latency thereof shouldn't depend on whether networking is up or down or what network the machine happened to be attached to at any given moment (like a laptop that travels between work and home).

[serge-sans-paille]

@davezarzycki I tend to agree with you. We can just remove 35:44 and just keep the hostname.

[labath]

In D67230#1661120, @serge-sans-paille wrote:

@davezarzycki I tend to agree with you. We can just remove 35:44 and just keep the hostname.

sounds good to me

[davezarzycki]

Great. See: r371596

lldb/trunk/source/Host/posix/HostInfoPosix.cpp

 using namespace lldb_private;
 
 size_t HostInfoPosix::GetPageSize() { return ::getpagesize(); }
 
 bool HostInfoPosix::GetHostname(std::string &s) {
   char hostname[PATH_MAX];
   hostname[sizeof(hostname) - 1] = '\0';
   if (::gethostname(hostname, sizeof(hostname) - 1) == 0) {
-    struct hostent *h = ::gethostbyname(hostname);
-    if (h)
-      s.assign(h->h_name);
-    else
+    struct addrinfo hints;
+    struct addrinfo *res = nullptr;
+    std::memset(&hints, 0, sizeof(hints));
+    hints.ai_flags = AI_CANONNAME;
+    int err = ::getaddrinfo(hostname, nullptr, &hints, &res);
+    if (err == 0) {
+      assert(res->ai_canonname && "getaddrinfo found a canonical name");
+      s.assign(res->ai_canonname);
+      freeaddrinfo(res);
+    } else
       s.assign(hostname);
     return true;
   }
   return false;
 }
 
 #ifdef __ANDROID__
 #include <android/api-level.h>