Index: trunk/src/obj_common.c
===================================================================
--- trunk/src/obj_common.c	(revision 10903)
+++ trunk/src/obj_common.c	(revision 10904)
@@ -154,3 +154,17 @@
 	if (strcmp(name, "term") == 0)
 		obj->term = value;
 }
+
+const char *pcb_obj_id_invalid(const char *id)
+{
+	const char *s;
+	for(s = id; *s != '\0'; s++) {
+		if (isalnum(*s))
+			continue;
+		switch(*s) {
+			case '_': case '.': case '$': case ':': continue;
+		}
+		return s;
+	}
+	return NULL;
+}
Index: trunk/src/obj_common.h
===================================================================
--- trunk/src/obj_common.h	(revision 10903)
+++ trunk/src/obj_common.h	(revision 10904)
@@ -161,6 +161,9 @@
 /* Update cached attributes (->term) */
 void pcb_obj_attrib_post_change(pcb_attribute_list_t *list, const char *name, const char *value);
 
+/* Returns the first invalid character of an ID (terminal, refdes) or NULL */
+const char *pcb_obj_id_invalid(const char *id);
+
 /* compare two fields and return 0 if they are equal */
 #define pcb_field_neq(s1, s2, f) ((s1)->f != (s2)->f)