silence compiler warnings for mingw win32 builds --enable-debug

lib/connect.c

@@ -364,6 +364,9 @@ static CURLcode bindlocal(struct connectdata *conn,
     return CURLE_OK;
 
   } /* end of device selection support */
+#else
+  (void)conn;
+  (void)sockfd;
 #endif /* end of HAVE_INET_NTOA */
 
   return CURLE_HTTP_PORT_FAILED;

lib/ftp.c

@@ -1062,7 +1062,7 @@ static CURLcode ftp_state_use_port(struct connectdata *conn,
       /* we set the secondary socket variable to this for now, it
          is only so that the cleanup function will close it in case
          we fail before the true secondary stuff is made */
-      if(-1 != conn->sock[SECONDARYSOCKET])
+      if(CURL_SOCKET_BAD != conn->sock[SECONDARYSOCKET])
         sclose(conn->sock[SECONDARYSOCKET]);
       conn->sock[SECONDARYSOCKET] = portsock;
 

lib/if2ip.h

@@ -24,12 +24,8 @@
  ***************************************************************************/
 #include "setup.h"
 
-#if !defined(WIN32) && !defined(__BEOS__) && !defined(__CYGWIN32__) && \
-    !defined(__riscos__) && !defined(__INTERIX)
-extern char *Curl_if2ip(const char *interface, char *buf, int buf_size);
-#else
-#define Curl_if2ip(a,b,c) NULL
-#endif
+extern char *Curl_if2ip(const char *interf, char *buf, int buf_size);
+
 #ifdef __INTERIX
 /* Nedelcho Stanev's work-around for SFU 3.0 */
 struct ifreq {

lib/strerror.c

@@ -346,7 +346,7 @@ curl_share_strerror(CURLSHcode error)
 static const char *
 get_winsock_error (int err, char *buf, size_t len)
 {
-  char *p;
+  const char *p;
 
 #ifndef CURL_DISABLE_VERBOSE_STRINGS
   switch (err) {