Now uses sigsetjmp() and siglongjmp() to bail out from slow name lookups in

case a timeout is set. This seems to work. God knows if it is good enough
or what kind of side-effects we introduce here and now.

I'll close my eyes and cross my fingers. Hard.

lib/hostip.c

@@ -56,6 +56,10 @@
 #endif
 #endif
 
+#ifdef HAVE_SETJMP_H
+#include <setjmp.h>
+#endif
+
 #include "urldata.h"
 #include "sendf.h"
 #include "hostip.h"
@@ -191,6 +195,11 @@ hostcache_prune(curl_hash *hostcache, int cache_timeout, int now)
   return (__v); \
 }
 
+#ifdef HAVE_SIGSETJMP
+/* Beware this is a global and unique instance */
+sigjmp_buf curl_jmpenv;
+#endif
+
 Curl_addrinfo *Curl_resolv(struct SessionHandle *data,
                            char *hostname,
                            int port)
@@ -201,6 +210,14 @@ Curl_addrinfo *Curl_resolv(struct SessionHandle *data,
   time_t now;
   char *bufp;
 
+#ifdef HAVE_SIGSETJMP
+  if(sigsetjmp(curl_jmpenv, 1) != 0) {
+    /* this is coming from a siglongjmp() */
+    failf(data, "name lookup time-outed");
+    return NULL;
+  }
+#endif
+
   /* If the host cache timeout is 0, we don't do DNS cach'ing
      so fall through */
   if (data->set.dns_cache_timeout == 0) {

lib/url.c

@@ -72,6 +72,10 @@
 #include <inet.h>
 #endif
 
+#ifdef HAVE_SETJMP_H
+#include <setjmp.h>
+#endif
+
 #ifndef HAVE_SELECT
 #error "We can't compile without select() support!"
 #endif
@@ -120,6 +124,7 @@
 #ifdef KRB4
 #include "security.h"
 #endif
+
 /* The last #include file should be: */
 #ifdef MALLOCDEBUG
 #include "memdebug.h"
@@ -143,6 +148,10 @@ RETSIGTYPE alarmfunc(int signal)
 {
   /* this is for "-ansi -Wall -pedantic" to stop complaining!   (rabe) */
   (void)signal;
+#ifdef HAVE_SIGSETJMP
+  extern sigjmp_buf curl_jmpenv;
+  siglongjmp(curl_jmpenv, 1);
+#endif
   return;
 }
 #endif