From 4f4c729547a7b116fa7da7c83128ee5a706351c5 Mon Sep 17 00:00:00 2001
From: Christian Mazakas <christian.mazakas@gmail.com>
Date: Mon, 9 Dec 2024 10:17:58 -0800
Subject: [PATCH] use manual pointer arithmetic to avoid invalid pointer cast

---
 include/boost/regex/v5/perl_matcher_non_recursive.hpp | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/include/boost/regex/v5/perl_matcher_non_recursive.hpp b/include/boost/regex/v5/perl_matcher_non_recursive.hpp
index 87400452..5a1c3f4c 100644
--- a/include/boost/regex/v5/perl_matcher_non_recursive.hpp
+++ b/include/boost/regex/v5/perl_matcher_non_recursive.hpp
@@ -237,8 +237,8 @@ void perl_matcher<BidiIterator, Allocator, traits>::extend_stack()
       saved_state* backup_state;
       stack_base = static_cast<saved_state*>(get_mem_block());
       backup_state = reinterpret_cast<saved_state*>(reinterpret_cast<char*>(stack_base)+BOOST_REGEX_BLOCKSIZE);
-      saved_extra_block* block = static_cast<saved_extra_block*>(backup_state);
-      --block;
+      saved_extra_block* block = reinterpret_cast<saved_extra_block*>(
+         reinterpret_cast<std::uintptr_t>(backup_state) - sizeof(saved_extra_block));
       (void) new (block) saved_extra_block(m_stack_base, m_backup_state);
       m_stack_base = stack_base;
       m_backup_state = block;