new loplugin:deadclass

look for classes which only have copy/move constructors, and so are
effectively dead

Change-Id: I0b844f301e2200c2b40031856bfdb0b0e2c8f77d
Reviewed-on: https://gerrit.libreoffice.org/41039
Tested-by: Jenkins <ci@libreoffice.org>
Reviewed-by: Noel Grandin <noel.grandin@collabora.co.uk>

2 files changed, 88 insertions, 0 deletions

diff --git a/compilerplugins/clang/deadclass.cxx b/compilerplugins/clang/deadclass.cxx
new file mode 100644
index 000000000000..1c14dd52d136
--- /dev/null
+++ b/compilerplugins/clang/deadclass.cxx
@@ -0,0 +1,74 @@
+/* -*- 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 "plugin.hxx"
+
+namespace {
+
+class DeadClass:
+    public RecursiveASTVisitor<DeadClass>, public loplugin::Plugin
+{
+public:
+    explicit DeadClass(InstantiationData const & data): Plugin(data) {}
+
+    void run() override;
+
+    bool VisitCXXRecordDecl(CXXRecordDecl const *);
+};
+
+void DeadClass::run() {
+    if (compiler.getLangOpts().CPlusPlus) {
+        TraverseDecl(compiler.getASTContext().getTranslationUnitDecl());
+    }
+}
+
+bool DeadClass::VisitCXXRecordDecl(CXXRecordDecl const * decl) {
+    if (ignoreLocation(decl) || !decl->isThisDeclarationADefinition())
+        return true;
+    if (decl->needsImplicitDefaultConstructor())
+        return true;
+    if (decl->getDescribedClassTemplate())
+        return true;
+    if (isa<ClassTemplateSpecializationDecl>(decl))
+        return true;
+    int otherCnt = 0;
+    int copyMoveCnt = 0;
+    for (auto i = decl->ctor_begin(); i != decl->ctor_end(); ++i) {
+        if (!i->isUserProvided())
+            continue;
+//        if (i->getTemplatedKind() != clang::FunctionDecl::TK_NonTemplate)
+//            return true;
+//        if (i->getTemplateInstantiationPattern())
+//            return true;
+        if (i->isCopyOrMoveConstructor())
+            copyMoveCnt++;
+        else
+            otherCnt++;
+    }
+    if (otherCnt == 0 && copyMoveCnt > 0)
+    {
+        report(
+            DiagnosticsEngine::Warning,
+            "class has only copy/move constructors, must be dead",
+            decl->getLocStart())
+            << decl->getSourceRange();
+        for (auto i = decl->ctor_begin(); i != decl->ctor_end(); ++i) {
+            if (i->isDeleted())
+                continue;
+            i->dump();
+        }
+    }
+    return true;
+}
+
+loplugin::Plugin::Registration<DeadClass> X("deadclass");
+
+}
+
+/* vim:set shiftwidth=4 softtabstop=4 expandtab: */
diff --git a/compilerplugins/clang/test/deadclass.cxx b/compilerplugins/clang/test/deadclass.cxx
new file mode 100644
index 000000000000..d8b9cdb60889
--- /dev/null
+++ b/compilerplugins/clang/test/deadclass.cxx
@@ -0,0 +1,14 @@
+/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4; fill-column: 100 -*- */
+/*
+ * 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/.
+ */
+
+struct Foo { // expected-error {{class has only copy/move constructors, must be dead [loplugin:deadclass]}}
+    Foo(Foo&);
+};
+
+/* vim:set shiftwidth=4 softtabstop=4 expandtab cinoptions=b1,g0,N-s cinkeys+=0=break: */