From e5474a557974bd50481812e9a5892be853384d4c Mon Sep 17 00:00:00 2001
From: Oleksandr Kulkov <adamant.pwn@gmail.com>
Date: Mon, 6 Oct 2025 00:08:23 +0200
Subject: [PATCH 1/3] Fix unaligned memory access UB in
 compact_vector::access()

Replace reinterpret_cast + dereference with memcpy to avoid undefined
behavior when accessing unaligned uint64_t values. This fixes crashes
and incorrect behavior on ARM64 where unaligned access is not tolerated.

The memcpy approach is standards-compliant and compilers optimize it to
efficient code on all platforms.
---
 include/compact_vector.hpp | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/include/compact_vector.hpp b/include/compact_vector.hpp
index 59c1753..75db609 100644
--- a/include/compact_vector.hpp
+++ b/include/compact_vector.hpp
@@ -2,6 +2,7 @@
 
 #include <vector>
 #include <cmath>
+#include <cstring>
 #include <iterator>
 
 #include "essentials.hpp"
@@ -253,7 +254,9 @@ struct compact_vector  //
         assert(i < size());
         uint64_t pos = i * m_width;
         const char* ptr = reinterpret_cast<const char*>(m_data.data());
-        return (*(reinterpret_cast<uint64_t const*>(ptr + (pos >> 3))) >> (pos & 7)) & m_mask;
+        uint64_t word;
+        std::memcpy(&word, ptr + (pos >> 3), sizeof(uint64_t));
+        return (word >> (pos & 7)) & m_mask;
     }
 
     uint64_t back() const { return operator[](size() - 1); }

From e16cea2998984fab6839ae269c3c727950b969c6 Mon Sep 17 00:00:00 2001
From: Oleksandr Kulkov <adamant.pwn@gmail.com>
Date: Mon, 6 Oct 2025 00:15:05 +0200
Subject: [PATCH 2/3] fix UB in append_bits

---
 include/bit_vector.hpp | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/include/bit_vector.hpp b/include/bit_vector.hpp
index ba0fb57..ea303ec 100644
--- a/include/bit_vector.hpp
+++ b/include/bit_vector.hpp
@@ -97,7 +97,7 @@ struct bit_vector  //
 
         void append_bits(uint64_t bits, uint64_t len) {
             // check there are no spurious bits
-            assert(len == 64 || (bits >> len) == 0);
+            assert(len >= 64 || (bits >> len) == 0);
             if (!len) return;
             uint64_t pos_in_word = m_num_bits & 63;
             m_num_bits += len;

From 74fb6937690adcd88f089f624b15362257cccf07 Mon Sep 17 00:00:00 2001
From: Oleksandr Kulkov <adamant.pwn@gmail.com>
Date: Mon, 6 Oct 2025 18:55:31 +0200
Subject: [PATCH 3/3] Fix assert

---
 include/bit_vector.hpp | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/include/bit_vector.hpp b/include/bit_vector.hpp
index ea303ec..9cd515f 100644
--- a/include/bit_vector.hpp
+++ b/include/bit_vector.hpp
@@ -97,7 +97,8 @@ struct bit_vector  //
 
         void append_bits(uint64_t bits, uint64_t len) {
             // check there are no spurious bits
-            assert(len >= 64 || (bits >> len) == 0);
+            assert(len <= 64);
+            assert(len == 64 || (bits >> len) == 0);
             if (!len) return;
             uint64_t pos_in_word = m_num_bits & 63;
             m_num_bits += len;