Merge pull request #21987 from vespa-engine/vekterli/make-buffertype-empty-entry-sentinel-static

Let empty entry BufferType sentinel be static instead of global [run-systemtest]

5 files changed, 18 insertions, 7 deletions

diff --git a/vespalib/src/vespa/vespalib/btree/btreenodestore.h b/vespalib/src/vespa/vespalib/btree/btreenodestore.h
index 444bf641899..d4a5ae42ef8 100644
--- a/vespalib/src/vespa/vespalib/btree/btreenodestore.h
+++ b/vespalib/src/vespa/vespalib/btree/btreenodestore.h
@@ -25,7 +25,7 @@ template <typename EntryType>
 class BTreeNodeBufferType : public datastore::BufferType<EntryType, FrozenBtreeNode<EntryType>>
 {
     using ParentType = datastore::BufferType<EntryType, FrozenBtreeNode<EntryType>>;
-    using ParentType::_emptyEntry;
+    using ParentType::empty_entry;
     using ParentType::_arraySize;
     using ElemCount = typename ParentType::ElemCount;
     using CleanContext = typename ParentType::CleanContext;
diff --git a/vespalib/src/vespa/vespalib/datastore/buffer_type.h b/vespalib/src/vespa/vespalib/datastore/buffer_type.h
index 7d041646ca5..3394af18b04 100644
--- a/vespalib/src/vespa/vespalib/datastore/buffer_type.h
+++ b/vespalib/src/vespa/vespalib/datastore/buffer_type.h
@@ -133,7 +133,7 @@ template <typename EntryType, typename EmptyType = EntryType>
 class BufferType : public BufferTypeBase
 {
 protected:
-    static EntryType _emptyEntry;
+    static const EntryType& empty_entry() noexcept;
 
 public:
     BufferType() noexcept : BufferType(1,1,1) {}
diff --git a/vespalib/src/vespa/vespalib/datastore/buffer_type.hpp b/vespalib/src/vespa/vespalib/datastore/buffer_type.hpp
index ae2659ef65b..72c8f574a70 100644
--- a/vespalib/src/vespa/vespalib/datastore/buffer_type.hpp
+++ b/vespalib/src/vespa/vespalib/datastore/buffer_type.hpp
@@ -51,8 +51,9 @@ void
 BufferType<EntryType, EmptyType>::initializeReservedElements(void *buffer, ElemCount reservedElems)
 {
     EntryType *e = static_cast<EntryType *>(buffer);
+    const auto& empty = empty_entry();
     for (size_t j = reservedElems; j != 0; --j) {
-        new (static_cast<void *>(e)) EntryType(_emptyEntry);
+        new (static_cast<void *>(e)) EntryType(empty);
         ++e;
     }
 }
@@ -62,13 +63,22 @@ void
 BufferType<EntryType, EmptyType>::cleanHold(void *buffer, size_t offset, ElemCount numElems, CleanContext)
 {
     EntryType *e = static_cast<EntryType *>(buffer) + offset;
+    const auto& empty = empty_entry();
     for (size_t j = numElems; j != 0; --j) {
-        *e = _emptyEntry;
+        *e = empty;
         ++e;
     }
 }
 
 template <typename EntryType, typename EmptyType>
-EntryType BufferType<EntryType, EmptyType>::_emptyEntry = EmptyType();
+const EntryType&
+BufferType<EntryType, EmptyType>::empty_entry() noexcept
+{
+    // It's possible for EntryType to wrap e.g. an Alloc instance, which has a transitive
+    // dependency on globally constructed allocator object(s). To avoid issues with global
+    // construction order, initialize the sentinel on the first access.
+    static EntryType empty = EmptyType();
+    return empty;
+}
 
 }
diff --git a/vespalib/src/vespa/vespalib/datastore/large_array_buffer_type.h b/vespalib/src/vespa/vespalib/datastore/large_array_buffer_type.h
index 50d15d4a27c..ccaedaa9b64 100644
--- a/vespalib/src/vespa/vespalib/datastore/large_array_buffer_type.h
+++ b/vespalib/src/vespa/vespalib/datastore/large_array_buffer_type.h
@@ -20,7 +20,7 @@ class LargeArrayBufferType : public BufferType<Array<EntryT>>
     using AllocSpec = ArrayStoreConfig::AllocSpec;
     using ArrayType = Array<EntryT>;
     using ParentType = BufferType<ArrayType>;
-    using ParentType::_emptyEntry;
+    using ParentType::empty_entry;
     using CleanContext = typename ParentType::CleanContext;
     std::shared_ptr<alloc::MemoryAllocator> _memory_allocator;
 public:
diff --git a/vespalib/src/vespa/vespalib/datastore/large_array_buffer_type.hpp b/vespalib/src/vespa/vespalib/datastore/large_array_buffer_type.hpp
index aeeef8166c6..3042bbff73f 100644
--- a/vespalib/src/vespa/vespalib/datastore/large_array_buffer_type.hpp
+++ b/vespalib/src/vespa/vespalib/datastore/large_array_buffer_type.hpp
@@ -22,9 +22,10 @@ void
 LargeArrayBufferType<EntryT>::cleanHold(void* buffer, size_t offset, ElemCount numElems, CleanContext cleanCtx)
 {
     ArrayType* elem = static_cast<ArrayType*>(buffer) + offset;
+    const auto& empty = empty_entry();
     for (size_t i = 0; i < numElems; ++i) {
         cleanCtx.extraBytesCleaned(sizeof(EntryT) * elem->size());
-        *elem = _emptyEntry;
+        *elem = empty;
         ++elem;
     }
 }