From: Patrick Palka <ppalka@redhat.com>
Date: Mon, 2 Feb 2026 20:14:20 +0000 (-0500)
Subject: libstdc++/regex: Zero-initialize _ExecutorFrame flags
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=8978da072f9ea7653416d59167a07e79be6cadaf;p=thirdparty%2Fgcc.git

libstdc++/regex: Zero-initialize _ExecutorFrame flags

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.

Reviewed-by: Jonathan Wakely <jwakely@redhat.com>
---

diff --git a/libstdc++-v3/include/bits/regex_executor.tcc b/libstdc++-v3/include/bits/regex_executor.tcc
index 6c8deff2f21..19b5ad27df4 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
 		{