https://github.com/bruceg/bglibs/pull/10

--- a/include/resolve.h
+++ b/include/resolve.h
@@ -26,7 +26,7 @@ extern int __resolve_error;
 #define resolve_error() (__resolve_error)
 
 struct dns_result;
-extern int resolve_calldns(int (*dnsfn)(), struct dns_result* out, const void* param);
+extern int resolve_calldns(int (*dnsfn)(struct dns_result*, const void*), struct dns_result* out, const void* param);
 extern int resolve_qualdns(int (*dnsfn)(struct dns_transmit*, struct dns_result* out, const char*),
                            struct dns_result* out, const char* name);
 
--- a/net/resolve_calldns.c
+++ b/net/resolve_calldns.c
@@ -5,7 +5,7 @@
 int __resolve_error = 0;
 
 /** Call a dns_* function and save an error code if necessary. */
-int resolve_calldns(int (*dnsfn)(), struct dns_result* out, const void* param)
+int resolve_calldns(int (*dnsfn)(struct dns_result*, const void*), struct dns_result* out, const void* param)
 {
   if (dnsfn(out, param) < 0) {
     __resolve_error = RESOLVE_TEMPFAIL;
--- a/net/resolve_ipv4addr.c
+++ b/net/resolve_ipv4addr.c
@@ -1,11 +1,15 @@
 #include "dns.h"
 #include "resolve.h"
 
+static int dns_name4_wrapper(struct dns_result *res, const void *ptr) {
+  return dns_name4(res, (const ipv4addr*)ptr);
+}
+
 /** Look up the domain name corresponding to an IPv4 address. */
 const char* resolve_ipv4addr(const ipv4addr* addr)
 {
   static struct dns_result out = {0};
-  if (!resolve_calldns(dns_name4, &out, addr))
+  if (!resolve_calldns(dns_name4_wrapper, &out, addr))
     return 0;
   return out.rr.name[0];
 }
--- a/sys/hassysselect.h0
+++ b/sys/hassysselect.h0
@@ -4,6 +4,5 @@
 /* sysdep: -sysselect */
 
 #include <sys/time.h>
-extern int select();
 
 #endif
--- a/sys/hassysselect.h1
+++ b/sys/hassysselect.h1
@@ -5,6 +5,5 @@
 
 #include <sys/time.h>
 #include <sys/select.h>
-extern int select();
 
 #endif
--- a/sys/hasvfork.h0
+++ b/sys/hasvfork.h0
@@ -2,7 +2,6 @@
 #define FORK_H
 
 /* sysdep: -vfork */
-extern pid_t fork();
 #define vfork fork
 
 #endif
--- a/sys/hasvfork.h1
+++ b/sys/hasvfork.h1
@@ -2,7 +2,5 @@
 #define FORK_H
 
 /* sysdep: +vfork */
-extern pid_t fork();
-extern pid_t vfork();
 
 #endif