--- a/src/shared/util.c	Tue Dec 29 15:38:31 2009 +0200
+++ b/src/shared/util.c	Tue Dec 29 16:44:48 2009 +0200
@@ -1,18 +1,23 @@
 #include "util.h"
 
 #include <string.h>
+#include <errno.h>
 
 int chfext (char *buf, size_t len, const char *newext)
 {
     char *ext;
 
     // find .ext
-    if ((ext = strrchr(buf, '.')) == NULL)
+    if ((ext = strrchr(buf, '.')) == NULL) {
+        errno = EINVAL;
         return -1;
+    }
 
     // check length
-    if (ext + strlen(newext) >= buf + len)
+    if (ext + strlen(newext) >= buf + len) {
+        errno = ENAMETOOLONG;
         return -1;
+    }
 
     // change to .foo
     strcpy(ext, newext);
@@ -24,8 +29,10 @@
 int path_with_fext (const char *path, char *buf, size_t len, const char *newext)
 {
     // verify length
-    if (strlen(path) > len)
+    if (strlen(path) > len) {
+        errno = ENAMETOOLONG;
         return -1;
+    }
 
     // copy filename
     strcpy(buf, path);