On Mon, 2 Feb 2026 at 14:35, Patrick Palka <[email protected]> wrote:
>
> Tested on x86_64-pc-linux-gnu, does this look OK for trunk?
Yes, thanks.
>
> -- >8 --
>
> Prevents uninitialized read bugs, and it's also just natural to assume
> flags are initially cleared rather than uninitialized.
>
> In passing rename the _M_end flag to _M_subexpr_end to make it distinct
> from _Executor::_M_end.
>
> libstdc++-v3/ChangeLog:
>
> * include/bits/regex_executor.tcc (_ExecutorFrameBase):
> Zero-initialize _M_byte0.
> (_ExecutorFrameBase::_M_end): Rename to ...
> (_ExecutorFrameBase::_M_subexpr_end): ... this.
> (_Executor::_M_handle_subexpr_begin): Remove now redundant
> clearing of _M_subexpr_end.
> (_Executor::_M_handle_subexpr_end): Adjust after renaming.
> (_Executor::_M_dfs) <case _S_fopcode_restore_cur_results>:
> Likewise.
> ---
> libstdc++-v3/include/bits/regex_executor.tcc | 9 ++++-----
> 1 file changed, 4 insertions(+), 5 deletions(-)
>
> diff --git a/libstdc++-v3/include/bits/regex_executor.tcc
> b/libstdc++-v3/include/bits/regex_executor.tcc
> index 6c8deff2f21e..19b5ad27df40 100644
> --- a/libstdc++-v3/include/bits/regex_executor.tcc
> +++ b/libstdc++-v3/include/bits/regex_executor.tcc
> @@ -79,12 +79,12 @@ _GLIBCXX_BEGIN_INLINE_ABI_NAMESPACE(_V2)
>
> _ExecutorFrameOpcode _M_op;
> union {
> - unsigned char _M_byte0;
> + unsigned char _M_byte0 = 0;
> struct { // Used by restore_rep_count frame
> unsigned char _M_count : 2;
> };
> struct { // Used by restore_cur_results frame
> - unsigned char _M_end : 1;
> + unsigned char _M_subexpr_end : 1;
> unsigned char _M_matched : 1;
> };
> };
> @@ -338,7 +338,6 @@ _GLIBCXX_BEGIN_INLINE_ABI_NAMESPACE(_V2)
> _M_frames.emplace_back(_S_fopcode_restore_cur_results,
> static_cast<_StateIdT>(__state._M_subexpr),
> __res.first);
> - _M_frames.back()._M_end = false;
> __res.first = _M_current;
> _M_frames.emplace_back(_S_fopcode_next, __state._M_next);
> }
> @@ -353,7 +352,7 @@ _GLIBCXX_BEGIN_INLINE_ABI_NAMESPACE(_V2)
> _M_frames.emplace_back(_S_fopcode_restore_cur_results,
> static_cast<_StateIdT>(__state._M_subexpr),
> __res.second);
> - _M_frames.back()._M_end = true;
> + _M_frames.back()._M_subexpr_end = true;
> _M_frames.back()._M_matched = __res.matched;
> __res.second = _M_current;
> __res.matched = true;
> @@ -670,7 +669,7 @@ _GLIBCXX_BEGIN_INLINE_ABI_NAMESPACE(_V2)
> break;
>
> case _S_fopcode_restore_cur_results:
> - if (!__frame._M_end)
> + if (!__frame._M_subexpr_end)
> _M_cur_results[__frame._M_state_id].first = __frame._M_pos;
> else
> {
> --
> 2.53.0.rc1.65.gea24e2c554
>
