-/** _lbx_fseek()
- * Seeks the specified file to the specified offset, given that the file is
- * currently positioned at *current. If the file does not support seeking,
- * and offset > *current, perform the seek by reading (and discarding) data.
- */
-int _lbx_fseek(FILE *f, long *current, size_t offset);
+#ifndef NDEBUG
+# define _lbx_dbgprint(str) (fprintf(stderr, str " [%s, %s:%d]\n", \
+ __func__, __FILE__, __LINE__))
+# define _lbx_assert(expr) ((!(expr)) \
+ ? (_lbx_dbgprint("format assertion failed: " #expr), 0) \
+ : 1)
+#else
+# define _lbx_dbgprint(str) 0
+# define _lbx_assert(expr) ((expr) ? 1 : 0)
+#endif