+struct msg_point msg_point_advance (struct msg_point, struct substring);
+
+/* Location of the cause of an error. */
+struct msg_location
+ {
+ /* Interned file name, or NULL. */
+ const char *file_name;
+
+ /* Nonnull if this came from a source file. */
+ struct lex_source *src;
+
+ /* The starting and ending point of the cause. One of:
+
+ - Both empty, with all their members zero.
+
+ - A range of lines, with 0 < start.line <= end.line and start.column =
+ end.column = 0.
+
+ - A range of columns spanning one or more lines. If it's on a single
+ line, then start.line = end.line and 0 < start.column <= end.column.
+ If it's across multiple lines, then 0 < start.line < end.line and the
+ column members are both positive.
+
+ Both 'start' and 'end' are inclusive, line-wise and column-wise.
+ */
+ struct msg_point start, end;
+
+ /* Normally, 'start' and 'end' contain column information, then displaying
+ the message will underline the location. Setting this to true disables
+ displaying underlines. */
+ bool omit_underlines;
+ };
+
+void msg_location_uninit (struct msg_location *);
+void msg_location_destroy (struct msg_location *);
+struct msg_location *msg_location_dup (const struct msg_location *);
+
+void msg_location_remove_columns (struct msg_location *);
+
+void msg_location_merge (struct msg_location **, const struct msg_location *);
+struct msg_location *msg_location_merged (const struct msg_location *,
+ const struct msg_location *);
+
+bool msg_location_is_empty (const struct msg_location *);
+void msg_location_format (const struct msg_location *, struct string *);
+
+struct msg_stack
+ {
+ struct msg_location *location;
+ char *description;
+ };
+
+void msg_stack_destroy (struct msg_stack *);
+struct msg_stack *msg_stack_dup (const struct msg_stack *);
+
+/* A message. */
+struct msg