Fails here:

        /* Make sure we handle a cyclic symbolic name, e.g. xx -> xx */
        cdio_realpath(psz_symlink_file, symlink_file);
        rc = check_rc(symlink(psz_symlink_file, psz_symlink_file),
                      "symlink", psz_symlink_file);
        if (0 == rc) {
            cdio_realpath(psz_symlink_file, psz_file_check);

Where psz_symlink_file is a symlink that points to itself and the problem is that cdio_realpath returns NULL and thus the content of symlink_file is undefined.

The following patches that:

diff --git a/test/driver/realpath.c b/test/driver/realpath.c
index 289253e4..4e85af96 100644
--- a/test/driver/realpath.c
+++ b/test/driver/realpath.c
@@ -175,14 +175,16 @@ main(int argc, const char *argv[])
         rc = check_rc(symlink(psz_symlink_file, psz_symlink_file),
                       "symlink", psz_symlink_file);
         if (0 == rc) {
-            cdio_realpath(psz_symlink_file, psz_file_check);
-            if (0 != strncmp(psz_file_check, symlink_file, PATH_MAX)) {
-                fprintf(stderr, "direct cdio_realpath cycle test failed. %s vs %s\n",
-                        psz_file_check, symlink_file);
- rc = 5;
- goto err_exit;
+            char *retvalue = cdio_realpath(psz_symlink_file, psz_file_check);
+            if (0 != retvalue) {
+                if (0 != strncmp(psz_file_check, symlink_file, PATH_MAX)) {
+                  fprintf(stderr, "direct cdio_realpath cycle test failed. %s vs %s\n",
+                      psz_file_check, symlink_file);
+                  rc = 5;
+                  goto err_exit;
+                }
+                check_rc(unlink(psz_symlink_file), "unlink", psz_symlink_file);
             }
-            check_rc(unlink(psz_symlink_file), "unlink", psz_symlink_file);
         }
 
     }