diff --git a/libasn1compiler/asn1c_compat.h b/libasn1compiler/asn1c_compat.h
index 9461b78..e80e2e7 100644
--- a/libasn1compiler/asn1c_compat.h
+++ b/libasn1compiler/asn1c_compat.h
@@ -5,6 +5,15 @@
 #include <config.h>
 #endif
 
+/*
+ * Open the arbitrary file by its base name and extension.
+ */
+FILE *asn1c_open_file(const char *base_part, const char *extension);
+
+/*
+ * Obtain base name and directory name of a path.
+ * Some systems have them in <libgen.h> as dirname(3) and basename(3).
+ */
 char *a1c_basename(const char *path);
 char *a1c_dirname(const char *path);