3 files changed, 110 insertions, 0 deletions
diff --git a/compilerplugins/clang/test/unusedindex.cxx b/compilerplugins/clang/test/unusedindex.cxx
new file mode 100644
index 000000000000..69ad7000b38c
--- /dev/null
+++ b/compilerplugins/clang/test/unusedindex.cxx
@@ -0,0 +1,23 @@
+/* -*- 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/.
+ */
+
+#include <vector>
+
+void func1()
+{
+    std::vector<int> v1;
+    int n = 0;
+
+    for (int i = 0; i < 10; ++i) // expected-error {{loop variable not used [loplugin:unusedindex]}}
+        n += 1;
+    for (int i = 0; i < 10; ++i)
+        n += i;
+}
+
+/* vim:set shiftwidth=4 softtabstop=4 expandtab cinoptions=b1,g0,N-s cinkeys+=0=break: */
diff --git a/compilerplugins/clang/unusedindex.cxx b/compilerplugins/clang/unusedindex.cxx
new file mode 100644
index 000000000000..96c343820a6b
--- /dev/null
+++ b/compilerplugins/clang/unusedindex.cxx
@@ -0,0 +1,86 @@
+
+/* -*- 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 <string>
+#include <iostream>
+#include <unordered_set>
+
+#include "plugin.hxx"
+#include "check.hxx"
+#include "clang/AST/CXXInheritance.h"
+#include "clang/AST/StmtVisitor.h"
+
+/*
+ Mike Kaganski found a bug where the code was looping over a block and
+ not using the index var, and the loop was unnecessary.
+ So he wanted to have a look for other places like that.
+*/
+namespace
+{
+class UnusedIndex : public RecursiveASTVisitor<UnusedIndex>, public loplugin::Plugin
+{
+public:
+    explicit UnusedIndex(loplugin::InstantiationData const& data)
+        : Plugin(data)
+    {
+    }
+
+    virtual void run() override { TraverseDecl(compiler.getASTContext().getTranslationUnitDecl()); }
+
+    bool TraverseForStmt(ForStmt* stmt);
+    bool VisitDeclRefExpr(DeclRefExpr const* stmt);
+
+private:
+    VarDecl const* mLoopVarDecl = nullptr;
+    std::unordered_set<VarDecl const*> mFoundSet;
+};
+
+bool UnusedIndex::TraverseForStmt(ForStmt* stmt)
+{
+    if (ignoreLocation(stmt))
+        return true;
+    auto savedCopy = mLoopVarDecl;
+
+    mLoopVarDecl = nullptr;
+    if (stmt->getInit())
+    {
+        auto declStmt = dyn_cast<DeclStmt>(stmt->getInit());
+        if (declStmt && declStmt->isSingleDecl())
+        {
+            auto varDecl = dyn_cast<VarDecl>(declStmt->getSingleDecl());
+            if (varDecl)
+                mLoopVarDecl = varDecl;
+        }
+    }
+
+    // deliberately ignore the other parts of the for stmt, except for the body
+    auto ret = RecursiveASTVisitor::TraverseStmt(stmt->getBody());
+
+    if (mLoopVarDecl && mFoundSet.erase(mLoopVarDecl) == 0)
+        report(DiagnosticsEngine::Warning, "loop variable not used", mLoopVarDecl->getLocStart())
+            << mLoopVarDecl->getSourceRange();
+    mLoopVarDecl = savedCopy;
+    return ret;
+}
+
+bool UnusedIndex::VisitDeclRefExpr(DeclRefExpr const* stmt)
+{
+    auto varDecl = dyn_cast<VarDecl>(stmt->getDecl());
+    if (!varDecl)
+        return true;
+    if (mLoopVarDecl && mLoopVarDecl == varDecl)
+        mFoundSet.insert(varDecl);
+    return true;
+}
+
+loplugin::Plugin::Registration<UnusedIndex> X("unusedindex", false);
+}
+
+/* vim:set shiftwidth=4 softtabstop=4 expandtab: */
diff --git a/solenv/CompilerTest_compilerplugins_clang.mk b/solenv/CompilerTest_compilerplugins_clang.mk
index 4a98ef996091..41990fab90f4 100644
--- a/solenv/CompilerTest_compilerplugins_clang.mk
+++ b/solenv/CompilerTest_compilerplugins_clang.mk
@@ -48,6 +48,7 @@ $(eval $(call gb_CompilerTest_add_exception_objects,compilerplugins_clang, \
     compilerplugins/clang/test/unnecessaryoverride-dtor \
     compilerplugins/clang/test/unnecessaryparen \
     compilerplugins/clang/test/unoany \
+    compilerplugins/clang/test/unusedindex \
     compilerplugins/clang/test/unusedvariablecheck \
     compilerplugins/clang/test/useuniqueptr \
     compilerplugins/clang/test/vclwidgets \