FIX: Fix misaligned reads in C++ DBN decoding

Author: threecgreen

CHANGELOG.md

@@ -1,5 +1,10 @@
 # Changelog
 
+## 0.15.0 - TBD
+
+### Bug fixes
+- Fixed misaligned read undefined behavior when decoding records
+
 ## 0.14.0 - 2023-11-23
 
 This release adds support for DBN v2.

include/databento/dbn_decoder.hpp

@@ -10,7 +10,7 @@
 #include "databento/detail/shared_channel.hpp"
 #include "databento/enums.hpp"  // Upgrade Policy
 #include "databento/ireadable.hpp"
-#include "databento/record.hpp"
+#include "databento/record.hpp"  // Record, RecordHeader
 
 namespace databento {
 // DBN decoder. Set upgrade_policy to control how DBN version 1 data should be
@@ -68,7 +68,9 @@ class DbnDecoder {
   std::unique_ptr<IReadable> input_;
   std::vector<std::uint8_t> read_buffer_;
   std::size_t buffer_idx_{};
-  std::array<std::uint8_t, kMaxRecordLen> compat_buffer_{};
+  // Must be 8-byte aligned for records
+  alignas(
+      RecordHeader) std::array<std::uint8_t, kMaxRecordLen> compat_buffer_{};
   Record current_record_{nullptr};
 };
 }  // namespace databento

include/databento/live_blocking.hpp

@@ -11,7 +11,7 @@
 #include "databento/dbn.hpp"                // Metadata
 #include "databento/detail/tcp_client.hpp"  // TcpClient
 #include "databento/enums.hpp"   // Schema, SType, VersionUpgradePolicy
-#include "databento/record.hpp"  // Record
+#include "databento/record.hpp"  // Record, RecordHeader
 
 namespace databento {
 class ILogReceiver;
@@ -93,10 +93,13 @@ class LiveBlocking {
   std::uint8_t version_{};
   VersionUpgradePolicy upgrade_policy_;
   detail::TcpClient client_;
-  std::array<char, kMaxStrLen> read_buffer_{};
+  // Must be 8-byte aligned for records
+  alignas(RecordHeader) std::array<char, kMaxStrLen> read_buffer_{};
   std::size_t buffer_size_{};
   std::size_t buffer_idx_{};
-  std::array<std::uint8_t, kMaxRecordLen> compat_buffer_{};
+  // Must be 8-byte aligned for records
+  alignas(
+      RecordHeader) std::array<std::uint8_t, kMaxRecordLen> compat_buffer_{};
   std::uint64_t session_id_;
   Record current_record_{nullptr};
 };