[kdevelop/kdevelop] kdevplatform/language/duchain: DUChain: stabilize the hash value of ReferencedTopDUContext

Git commit dfca0399fb72d910df0b8ba353f85c9f8fce5d88 by Jarmo Tiitto.
Committed on 02/08/2026 at 13:12.
Pushed by jatothrim into branch 'master'.

DUChain: stabilize the hash value of ReferencedTopDUContext

ReferencedTopDUContext hash value is currently computed from a unstable
m_topContext pointer value. Moreover, the returned value is consumed by
QSet<ReferencedTopDUContext> DUChain::m_openDocumentContexts, which
therefore mandates a size_t (64-bit) hash value to be used.

m_topContext->ownIndex() is a persistent unique index of TopDUContext
serialized as TopDUContextData::m_ownIndex. The TopDUContext indexes are
reserved with DUChain::newTopContextIndex(). Compute the hash instead
based on the m_topContext->ownIndex() using qHash() to expand and mix it
as a 64-bit value. This makes the hash value stable across multiple
session reloads.

M  +8    -0    kdevplatform/language/duchain/topducontext.cpp
M  +1    -4    kdevplatform/language/duchain/topducontext.h

https://invent.kde.org/kdevelop/kdevelop/-/commit/dfca0399fb72d910df0b8ba353f85c9f8fce5d88

diff --git a/kdevplatform/language/duchain/topducontext.cpp b/kdevplatform/language/duchain/topducontext.cpp
index 2b4b7bc27c..f1526d694a 100644
--- a/kdevplatform/language/duchain/topducontext.cpp
+++ b/kdevplatform/language/duchain/topducontext.cpp
@@ -28,6 +28,7 @@
 
 #include <language/interfaces/iastcontainer.h>
 
+#include <QHash>
 #include <QMutexLocker>
 #include <QRecursiveMutex>
 
@@ -77,6 +78,13 @@ ReferencedTopDUContext& ReferencedTopDUContext::operator=(const ReferencedTopDUC
     return *this;
 }
 
+size_t ReferencedTopDUContext::hash() const
+{
+    // This must be based on a unique disk-persistent value of m_topContext and return a 64-bit hash.
+    Q_ASSERT(m_topContext);
+    return ::qHash(size_t(m_topContext->ownIndex()));
+}
+
 DEFINE_LIST_MEMBER_HASH(TopDUContextData, m_usedDeclarationIds, DeclarationId)
 DEFINE_LIST_MEMBER_HASH(TopDUContextData, m_problems, LocalIndexedProblem)
 REGISTER_DUCHAIN_ITEM(TopDUContext);
diff --git a/kdevplatform/language/duchain/topducontext.h b/kdevplatform/language/duchain/topducontext.h
index 21ebedced6..e768433a4d 100644
--- a/kdevplatform/language/duchain/topducontext.h
+++ b/kdevplatform/language/duchain/topducontext.h
@@ -80,10 +80,7 @@ public:
         return m_topContext;
     }
 
-    inline uint hash() const
-    {
-        return ( uint )((( quint64 )m_topContext) * 37);
-    }
+    size_t hash() const;
 
 private:
     TopDUContext* m_topContext;