+/*----------.
+| --trace. |
+`----------*/
+enum trace
+ {
+ trace_none = 0, /**< No traces. */
+ trace_scan = 1 << 0, /**< Grammar scanner traces. */
+ trace_parse = 1 << 1, /**< Grammar parser traces. */
+ trace_resource = 1 << 2, /**< Memory allocation. */
+ trace_sets = 1 << 3, /**< Grammar sets: firsts, nullable etc. */
+ trace_bitsets = 1 << 4, /**< Use of bitsets. */
+ trace_tools = 1 << 5, /**< m4 invocation. */
+ trace_automaton = 1 << 6, /**< Construction of the automaton. */
+ trace_grammar = 1 << 7, /**< Reading, reducing the grammar. */
+ trace_time = 1 << 8, /**< Time consumption. */
+ trace_skeleton = 1 << 9, /**< Skeleton postprocessing. */
+ trace_m4 = 1 << 10, /**< M4 traces. */
+ trace_muscles = 1 << 11, /**< M4 definitions of the muscles. */
+ trace_ielr = 1 << 12, /**< IELR conversion. */
+ trace_all = ~0 /**< All of the above. */
+ };
+/** What debug items bison displays during its run. */
+extern int trace_flag;
+
+/*-------------.
+| --features. |
+`-------------*/
+
+enum feature
+ {
+ feature_none = 0, /**< No additional feature. */
+ feature_caret = 1 << 0, /**< Enhance the output of errors with carets. */
+ feature_all = ~0 /**< All above features. */
+ };
+/** What additional features to use. */
+extern int feature_flag;
+
+/** Process the command line arguments.
+ *
+ * \param argc size of \a argv
+ * \param argv list of arguments.
+ */