Woops, partly revert my previous commit and do it slightly differently instead.

The signalling of that a global DNS cache is wanted is done by setting the
option but the setting of the internal variable that it is in use must not be
done until it finally actually gets used!

NOTE and WARNING: I noticed that you can't actually switch off the global dns
cache with CURLOPT_DNS_USE_GLOBAL_CACHE but you couldn't do that previously
either and the option is very clearly and loudly documented as DO NOTE USE so
I won't bother to fix this bug now.

1 files changed, 2 insertions, 7 deletions

diff --git a/lib/url.c b/lib/url.c
index 94c363fc2..83ebcfefa 100644
--- a/lib/url.c
+++ b/lib/url.c
@@ -778,14 +778,9 @@ CURLcode Curl_setopt(struct SessionHandle *data, CURLoption option,
     break;
   case CURLOPT_DNS_USE_GLOBAL_CACHE:
     {
+      /* remember we want this enabled */
       long use_cache = va_arg(param, long);
-      if(use_cache) {
-        Curl_global_host_cache_init();
-        data->dns.hostcachetype = HCACHE_GLOBAL;
-      }
-      else
-        /* not global makes it private by default then */
-        data->dns.hostcachetype = HCACHE_PRIVATE;
+      data->set.global_dns_cache = (bool)(0 != use_cache);
     }
     break;
   case CURLOPT_SSL_CIPHER_LIST: