This patch replaces the recursive implementation of the DFS executor
with an iterative one using an explicit heap-based stack. System
stack usage of the executor is now constant with respect to input size
rather than linear, avoding stack overflow errors when processing
long inputs.
PR libstdc++/86164
libstdc++-v3/ChangeLog:
* include/bits/regex.h (__detail::_Executor): Use inline
namespace _V2.
* include/bits/regex_executor.h (__detail::_ExecutorFrame):
Declare.
(__detail::_Executor): Use inline namespace _V2.
(__detail::_Executor::_M_node): Declare.
(__detail::_Executor::_M_frames): New data member.
* include/bits/regex_executor.tcc (__detail::_ExecutorFrameOpcode):
New.
(__detail::_ExecutorFrameBase): New.
(__detail::_ExecutorFrame): New.
(__detail::_Executor): Use inline namespace _V2.
(__detail::_Executor::_M_rep_once_more): Replace recursive
_M_dfs calls with an _S_opcode_next frame push, and any work
after such calls with an appropriate frame push.
(__detail::_M_handle_repeat): Likewise.
(__detail::_M_handle_subexpr_begin): Likewise.
(__detail::_M_handle_subexpr_end): Likewise.
(__detail::_M_handle_line_begin_assertion): Likewise.
(__detail::_M_handle_line_end_assertion): Likewise.
(__detail::_M_handle_word_boundary): Likewise.
(__detail::_M_handle_subexpr_lookahead): Likewise.
(__detail::_M_handle_match): Likewise.
(__detail::_M_handle_backref): Likewise.
(__detail::_M_handle_accept): Likewise.
(__detail::_M_handle_alternative): Likewise.
(__detail::_M_node): Factored out from _M_dfs.
(__detail::_M_dfs): Push an initial frame to _M_frames that
visits the starting node and pass this stack each subroutine.
Pop the latest _ExecutorFrame from _M_frames and handle
appropriately according to its _ExecutorFrameOpcode. Loop until
_M_frames is empty.
Reviewed-by: Tomasz Kamiński <tkaminsk@redhat.com>
Reviewed-by: Jonathan Wakely <jwakely@redhat.com>
158ad5f969