1 files changed, 88 insertions, 0 deletions
diff --git a/compilerplugins/clang/cow_wrapper.cxx b/compilerplugins/clang/cow_wrapper.cxx
new file mode 100644
index 000000000000..4c04674f65c1
--- /dev/null
+++ b/compilerplugins/clang/cow_wrapper.cxx
@@ -0,0 +1,88 @@
+/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*- */
+/*
+ * This file is part of the LibreOffice project.
+ *
+ * Based on LLVM/Clang.
+ *
+ * This file is distributed under the University of Illinois Open Source
+ * License. See LICENSE.TXT for details.
+ *
+ */
+#ifndef LO_CLANG_SHARED_PLUGINS
+
+#include <cassert>
+#include <string>
+#include <iostream>
+#include <fstream>
+#include <set>
+#include <unordered_set>
+#include "plugin.hxx"
+#include "check.hxx"
+
+/*
+Look for places where we are using cow_wrapper, but we are calling a const method on the impl object
+with a non-const pointer, which means we will unnnecessarily trigger a copy.
+*/
+
+namespace
+{
+class Cow_Wrapper : public loplugin::FilteringPlugin<Cow_Wrapper>
+{
+public:
+    explicit Cow_Wrapper(loplugin::InstantiationData const& data)
+        : FilteringPlugin(data)
+    {
+    }
+
+    virtual bool preRun() override { return true; }
+
+    virtual void run() override
+    {
+        if (preRun())
+            TraverseDecl(compiler.getASTContext().getTranslationUnitDecl());
+    }
+
+    bool VisitCXXMemberCallExpr(const CXXMemberCallExpr*);
+};
+
+bool Cow_Wrapper::VisitCXXMemberCallExpr(const CXXMemberCallExpr* memberCallExpr)
+{
+    if (ignoreLocation(memberCallExpr))
+        return true;
+    auto methodDecl = memberCallExpr->getMethodDecl();
+    if (!methodDecl || !methodDecl->isConst())
+        return true;
+
+    auto operatorCallExpr = dyn_cast<CXXOperatorCallExpr>(
+        compat::IgnoreImplicit(memberCallExpr->getImplicitObjectArgument()));
+    if (!operatorCallExpr)
+        return true;
+    if (operatorCallExpr->getOperator() != OO_Arrow)
+        return true;
+    auto arrowMethodDecl = dyn_cast_or_null<CXXMethodDecl>(operatorCallExpr->getDirectCallee());
+    if (!arrowMethodDecl)
+        return true;
+    if (arrowMethodDecl->isConst())
+        return true;
+    auto dc = loplugin::DeclCheck(arrowMethodDecl->getParent())
+                  .Class("cow_wrapper")
+                  .Namespace("o3tl")
+                  .GlobalNamespace();
+    if (!dc)
+        return true;
+
+    report(DiagnosticsEngine::Warning,
+           "calling const method on o3tl::cow_wrapper impl class via non-const pointer, rather use "
+           "std::as_const to prevent triggering an unnecessary copy",
+           compat::getBeginLoc(memberCallExpr))
+        << memberCallExpr->getSourceRange();
+    return true;
+}
+
+loplugin::Plugin::Registration<Cow_Wrapper> cow_wrapper("cow_wrapper", true);
+
+} // namespace
+
+#endif // LO_CLANG_SHARED_PLUGINS
+
+/* vim:set shiftwidth=4 softtabstop=4 expandtab: */