Keith McGuigan's excellent fix that makes a cloned copy of the hostent struct

for when gethostbyname() is used so that we have the memory of the struct
allocated. This turns out to be needed if the curl handled is passed between
threads on Windows and possibly other operating systems where we use that
function.

lib/hostip.c

@@ -94,6 +94,75 @@ Curl_addrinfo *Curl_getaddrinfo(struct SessionHandle *data,
 }
 #else /* following code is IPv4-only */
 
+/**
+ * Performs a "deep" copy of a hostent into a buffer 
+ * (returns a pointer to the copy).
+ *
+ * Keith McGuigan 
+ * 10/3/2001
+ */
+static struct hostent* pack_hostent(char* buf, struct hostent* orig)
+{
+  char* bufptr;
+  struct hostent* copy;
+
+  int i;
+  char* str;
+  int len;
+
+  bufptr = buf;
+  copy = (struct hostent*)bufptr;
+
+  bufptr += sizeof(struct hostent);
+  copy->h_name = bufptr;
+  len = strlen(orig->h_name) + 1;
+  strncpy(bufptr, orig->h_name, len);
+  bufptr += len;
+
+  copy->h_aliases = (char**)bufptr;
+
+  /* Figure out how many aliases there are */
+  for (i = 0; orig->h_aliases[i] != NULL; ++i);
+
+  /* Reserve room for the array */
+  bufptr += (i + 1) * sizeof(char*);
+
+  i = 0;
+  str = orig->h_aliases[i];
+  while (str != NULL) {
+    len = strlen(str) + 1;
+    strncpy(bufptr, str, len);
+    copy->h_aliases[i] = bufptr;
+    bufptr += len;
+    str = orig->h_aliases[++i];
+  }
+  copy->h_aliases[i] = NULL;
+
+  copy->h_addrtype = orig->h_addrtype;
+  copy->h_length = orig->h_length;
+    
+  copy->h_addr_list = (char**)bufptr;
+
+  /* Figure out how many addresses there are */
+  for (i = 0; orig->h_addr_list[i] != NULL; ++i);
+
+  /* Reserve room for the array */
+  bufptr += (i + 1) * sizeof(char*);
+
+  i = 0;
+  len = orig->h_length;
+  str = orig->h_addr_list[i];
+  while (str != NULL) {
+    memcpy(bufptr, str, len);
+    copy->h_addr_list[i] = bufptr;
+    bufptr += len;
+    str = orig->h_addr_list[++i];
+  }
+  copy->h_addr_list[i] = NULL;
+
+  return copy;
+}
+
 static char *MakeIP(unsigned long num,char *addr, int addr_len)
 {
 #if defined(HAVE_INET_NTOA) || defined(HAVE_INET_NTOA_R)
@@ -217,6 +286,11 @@ Curl_addrinfo *Curl_getaddrinfo(struct SessionHandle *data,
       free(buf);
       *bufp=NULL;
     }
+    else 
+      /* we make a copy of the hostent right now, right here, as the
+         static one we got a pointer to might get removed when we don't
+         want/expect that */
+      h = pack_hostent(buf, h);
 #endif
   }
   return (h);