diff --git a/libraries/AP_HAL_ChibiOS/hwdef/common/posix.c b/libraries/AP_HAL_ChibiOS/hwdef/common/posix.c
index a5f842ae21..70b05cbf5f 100644
--- a/libraries/AP_HAL_ChibiOS/hwdef/common/posix.c
+++ b/libraries/AP_HAL_ChibiOS/hwdef/common/posix.c
@@ -109,6 +109,7 @@ along with this program.  If not, see <http://www.gnu.org/licenses/>.
 
 #include <string.h>
 #include "posix.h"
+#include "stdio.h"
 #undef strerror_r
 
 ///  Note: fdevopen assigns stdin,stdout,stderr
@@ -231,7 +232,6 @@ fgetc(FILE *stream)
     } else {
         if(!stream->get)
         {
-            printf("fgetc stream->get NULL\n");
             return(EOF);
         }
         // get character from device or file
@@ -266,13 +266,6 @@ fputc(int c, FILE *stream)
     errno = 0;
     int ret;
 
-    if(stream == NULL)
-    {
-        errno = EBADF;                            // Bad File Number
-        return(EOF);
-    }
-
-
     if(stream != stdout && stream != stderr)
     {
         return(fatfs_putc(c,stream));
@@ -291,7 +284,6 @@ fputc(int c, FILE *stream)
     } else {
         if(!stream->put)
         {
-            printf("fputc stream->put NULL\n");
             return(EOF);
         }
         ret = stream->put(c, stream);
@@ -1225,7 +1217,8 @@ ssize_t write(int fd, const void *buf, size_t count)
 
 FILE * __wrap_freopen ( const char * filename, const char * mode, FILE * stream )
 {
-    int ret = close(stream);
+    int fn = fileno(stream);
+    int ret = close(fn);
     if (ret < 0) {
         return NULL;
     }
@@ -1411,7 +1404,7 @@ int utime(const char *filename, const struct utimbuf *times)
 
 int64_t fs_getfree() {
     FATFS *fs;
-    DWORD fre_clust, fre_sect, tot_sect;
+    DWORD fre_clust, fre_sect;
 
 
     /* Get volume information and free clusters of drive 1 */
@@ -1426,7 +1419,7 @@ int64_t fs_getfree() {
 
 int64_t fs_gettotal() {
     FATFS *fs;
-    DWORD fre_clust, fre_sect, tot_sect;
+    DWORD fre_clust, tot_sect;
 
 
     /* Get volume information and free clusters of drive 1 */
@@ -2238,7 +2231,6 @@ int fatfs_to_fileno(FIL *fh)
  */
 static time_t replace_mktime(const struct tm *t)
 {
-    struct tm       *u;
     time_t  epoch = 0;
     int n;
     int mon [] = { 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31 }, y, m, i;
diff --git a/libraries/AP_HAL_ChibiOS/hwdef/common/stdio.c b/libraries/AP_HAL_ChibiOS/hwdef/common/stdio.c
index e823b5522d..ce15a2b571 100644
--- a/libraries/AP_HAL_ChibiOS/hwdef/common/stdio.c
+++ b/libraries/AP_HAL_ChibiOS/hwdef/common/stdio.c
@@ -28,6 +28,7 @@
 #include <hal.h>
 #include <memstreams.h>
 #include <chprintf.h>
+#include <ctype.h>
 #include "stdio.h"
 
 int vsnprintf(char *str, size_t size, const char *fmt, va_list ap)
@@ -236,7 +237,8 @@ atob(uint32_t *vp, char *p, int base)
 int
 vsscanf (const char *buf, const char *s, va_list ap)
 {
-    int             count, noassign, width, base, lflag;
+    int             count, noassign, base=0, lflag;
+    uint32_t width;
     const char     *tc;
     char           *t, tmp[MAXLN];
 
@@ -318,6 +320,8 @@ vsscanf (const char *buf, const char *s, va_list ap)
     return (count);
 }
 
+static int vfscanf(FILE *stream, const char *fmt, va_list ap);
+
 /*
  *  fscanf(stream,fmt,va_alist)
  */