@deftypefun void yy_pop_state ()
pops the top of the stack and switches to it via
@code{BEGIN}.
+The program execution aborts, if there is no state on the stack.
@end deftypefun
@deftypefun int yy_top_state ()
-returns the top of the stack without altering the stack's contents.
+returns the top of the stack without altering the stack's contents
+if a top state on the stack exists or the current state via
+@code{YY_START}
+otherwise.
@end deftypefun
@cindex memory, for start condition stacks
The start condition stack grows dynamically and so has no built-in size
limitation. If memory is exhausted, program execution aborts.
+The stack is not automatically reset. The function
+@code{yylex_destroy}
+should be called to reset and destroy the state stack which then frees
+other resources used by the scanner.
To use start condition stacks, your scanner must include a @code{%option
stack} directive (@pxref{Scanner Options}).