new loplugin:trivialdestructor

look for potentially trivial destructors that can then be elided

Change-Id: I435c251bd4291b5864c20d68f88676faac7c43fb
Reviewed-on: https://gerrit.libreoffice.org/c/core/+/131318
Tested-by: Jenkins
Reviewed-by: Noel Grandin <noel.grandin@collabora.co.uk>

1 files changed, 133 insertions, 0 deletions

diff --git a/compilerplugins/clang/trivialdestructor.cxx b/compilerplugins/clang/trivialdestructor.cxx
new file mode 100644
index 000000000000..208e4931a152
--- /dev/null
+++ b/compilerplugins/clang/trivialdestructor.cxx
@@ -0,0 +1,133 @@
+/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*- */
+/*
+ * This file is part of the LibreOffice project.
+ *
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/.
+ */
+
+#include <cassert>
+#include <string>
+#include <iostream>
+#include <unordered_map>
+#include <unordered_set>
+
+#include "plugin.hxx"
+#include "check.hxx"
+#include "config_clang.h"
+#include "clang/AST/CXXInheritance.h"
+#include "clang/AST/StmtVisitor.h"
+
+// Look for explicit destructors that can be trivial (and therefore don't need to be declared)
+
+namespace
+{
+class TrivialDestructor : public loplugin::FilteringPlugin<TrivialDestructor>
+{
+public:
+    explicit TrivialDestructor(loplugin::InstantiationData const& data)
+        : FilteringPlugin(data)
+    {
+    }
+
+    virtual void run() override { TraverseDecl(compiler.getASTContext().getTranslationUnitDecl()); }
+
+    bool VisitCXXDestructorDecl(CXXDestructorDecl const*);
+
+private:
+    bool HasTrivialDestructorBody(const CXXRecordDecl* BaseClassDecl,
+                                  const CXXRecordDecl* MostDerivedClassDecl);
+    bool FieldHasTrivialDestructorBody(const FieldDecl* Field);
+};
+
+bool TrivialDestructor::VisitCXXDestructorDecl(CXXDestructorDecl const* destructorDecl)
+{
+    if (ignoreLocation(destructorDecl))
+        return true;
+    if (!destructorDecl->hasTrivialBody())
+        return true;
+    if (destructorDecl->isVirtual())
+        return true;
+    if (destructorDecl->getExceptionSpecType() != EST_None)
+        return true;
+    if (destructorDecl->getAccess() != AS_public)
+        return true;
+    if (isInUnoIncludeFile(
+            compiler.getSourceManager().getSpellingLoc(destructorDecl->getLocation())))
+        return true;
+    if (!HasTrivialDestructorBody(destructorDecl->getParent(), destructorDecl->getParent()))
+        return true;
+
+    report(DiagnosticsEngine::Warning, "no need for explicit destructor decl",
+           destructorDecl->getLocation())
+        << destructorDecl->getSourceRange();
+    if (destructorDecl->getCanonicalDecl() != destructorDecl)
+    {
+        destructorDecl = destructorDecl->getCanonicalDecl();
+        report(DiagnosticsEngine::Warning, "no need for explicit destructor decl",
+               destructorDecl->getLocation())
+            << destructorDecl->getSourceRange();
+    }
+    return true;
+}
+
+bool TrivialDestructor::HasTrivialDestructorBody(const CXXRecordDecl* BaseClassDecl,
+                                                 const CXXRecordDecl* MostDerivedClassDecl)
+{
+    if (BaseClassDecl != MostDerivedClassDecl && !BaseClassDecl->hasTrivialDestructor())
+        return false;
+
+    // Check fields.
+    for (const auto* field : BaseClassDecl->fields())
+        if (!FieldHasTrivialDestructorBody(field))
+            return false;
+
+    // Check non-virtual bases.
+    for (const auto& I : BaseClassDecl->bases())
+    {
+        if (I.isVirtual())
+            continue;
+        if (!I.getType()->isRecordType())
+            continue;
+        const CXXRecordDecl* NonVirtualBase = I.getType()->getAsCXXRecordDecl();
+        if (NonVirtualBase && !HasTrivialDestructorBody(NonVirtualBase, MostDerivedClassDecl))
+            return false;
+    }
+
+    if (BaseClassDecl == MostDerivedClassDecl)
+    {
+        // Check virtual bases.
+        for (const auto& I : BaseClassDecl->vbases())
+        {
+            if (!I.getType()->isRecordType())
+                continue;
+            const CXXRecordDecl* VirtualBase = I.getType()->getAsCXXRecordDecl();
+            if (VirtualBase && !HasTrivialDestructorBody(VirtualBase, MostDerivedClassDecl))
+                return false;
+        }
+    }
+    return true;
+}
+
+bool TrivialDestructor::FieldHasTrivialDestructorBody(const FieldDecl* Field)
+{
+    QualType FieldBaseElementType = compiler.getASTContext().getBaseElementType(Field->getType());
+
+    const RecordType* RT = FieldBaseElementType->getAs<RecordType>();
+    if (!RT)
+        return true;
+
+    CXXRecordDecl* FieldClassDecl = cast<CXXRecordDecl>(RT->getDecl());
+
+    // The destructor for an implicit anonymous union member is never invoked.
+    if (FieldClassDecl->isUnion() && FieldClassDecl->isAnonymousStructOrUnion())
+        return false;
+
+    return FieldClassDecl->hasTrivialDestructor();
+}
+
+loplugin::Plugin::Registration<TrivialDestructor> X("trivialdestructor", true);
+}
+
+/* vim:set shiftwidth=4 softtabstop=4 expandtab: */