For the record, I went with (4), grabbing the machine's configuration to pull together the hostname the daemon is using without having to query it.
static char* getBonjourDefaultHost()
{
char* rv = 0;
#ifdef __APPLE__
CFStringRef name = SCDynamicStoreCopyLocalHostName(NULL);
if (name) {
int len = CFStringGetLength(name);
rv = new char[len*4+1];
CFStringGetCString(name, rv, len*4+1, kCFStringEncodingUTF8);
CFRelease(name);
}
// This fallback is completely incorrect, but why should we care...
// Mac does something crazy like <sysctl hw.model>-<MAC address>.
if (!rv)
rv = GetHostname(); // using gethostname(2)
#elif defined(WIN32)
CHAR tmp[256+1];
ULONG namelength = sizeof(tmp);
DynamicFn<BOOL (WINAPI*)(COMPUTER_NAME_FORMAT,LPSTR,LPDWORD)>
GetComputerNameExA_("Kernel32", "GetComputerNameExA");
if (!GetComputerNameExA_.isValid() ||
!(*GetComputerNameExA_)(ComputerNamePhysicalDnsHostname, tmp, &namelength))
tmp[0] = 0;
// Roughly correct; there's some obscure string cleaning mDNSResponder does
// to tidy up funny international strings.
rv = tmp[0] ? strdup(tmp) : strdup("My Computer");
#elif defined(__sun)
// This is exactly correct! What a relief.
rv = GetHostName();
#else
#error Must add platform mDNS daemon scheme
#endif
return rv;
}