1 files changed, 125 insertions, 0 deletions
diff --git a/compilerplugins/clang/unusedvariablecheck.cxx b/compilerplugins/clang/unusedvariablecheck.cxx
new file mode 100644
index 000000000..f15521994
--- /dev/null
+++ b/compilerplugins/clang/unusedvariablecheck.cxx
@@ -0,0 +1,125 @@
+/* -*- 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 <config_global.h>
+
+#include "compat.hxx"
+#include "check.hxx"
+#include "unusedvariablecheck.hxx"
+#include "plugin.hxx"
+
+namespace loplugin
+{
+
+/*
+This is a compile check.
+
+Check for unused classes where the compiler cannot decide (e.g. because of
+non-trivial or extern ctors) if a variable is unused if only its ctor/dtor
+are called and nothing else. For example std::vector is a class where
+the ctor may call further functions, but an unused std::string variable
+does nothing. On the other hand, std::scoped_lock instances are used
+for their dtors and so are not unused even if not otherwise accessed.
+
+Classes which are safe to be warned about need to be marked using
+SAL_WARN_UNUSED (see e.g. OUString). For external classes such as std::vector
+that cannot be edited there is a manual list below.
+*/
+
+UnusedVariableCheck::UnusedVariableCheck( const InstantiationData& data )
+    : FilteringPlugin( data )
+    {
+    }
+
+void UnusedVariableCheck::run()
+    {
+    TraverseDecl( compiler.getASTContext().getTranslationUnitDecl());
+    }
+
+bool UnusedVariableCheck::VisitVarDecl( const VarDecl* var )
+    {
+    if( ignoreLocation( var ))
+        return true;
+    if( var->isReferenced() || var->isUsed())
+        return true;
+    if( var->isDefinedOutsideFunctionOrMethod())
+        return true;
+
+    auto type = var->getType();
+    bool check = loplugin::isExtraWarnUnusedType(type);
+
+    if (!check)
+        check = isUnusedSmartPointer(var);
+
+
+    // this chunk of logic generates false+, which is why we don't leave it on
+/*
+    if (!check && type->isRecordType())
+    {
+        auto recordDecl
+            = dyn_cast_or_null<CXXRecordDecl>(type->getAs<RecordType>()->getDecl());
+        if (recordDecl && recordDecl->hasDefinition() && recordDecl->hasTrivialDestructor())
+            check = true;
+    }
+*/
+    if(check)
+        {
+            if( const ParmVarDecl* param = dyn_cast< ParmVarDecl >( var ))
+                {
+                if( !param->getDeclName())
+                    return true; // unnamed parameter -> unused
+                // If this declaration does not have a body, then the parameter is indeed not used,
+                // so ignore.
+                auto const parent = param->getParentFunctionOrMethod();
+                if( const FunctionDecl* func = dyn_cast_or_null< FunctionDecl >( parent))
+                    if( !func->doesThisDeclarationHaveABody() || func->getBody() == nullptr)
+                        return true;
+                if (auto const d = dyn_cast_or_null<ObjCMethodDecl>(parent)) {
+                    if (!d->hasBody()) {
+                        return true;
+                    }
+                }
+                report( DiagnosticsEngine::Warning, "unused parameter %0",
+                    var->getLocation()) << var->getDeclName();
+                }
+            else
+                report( DiagnosticsEngine::Warning, "unused variable %0",
+                    var->getLocation()) << var->getDeclName();
+        }
+    return true;
+    }
+
+bool UnusedVariableCheck::isUnusedSmartPointer( const VarDecl* var )
+    {
+        // if we have a var of smart-pointer type, and that var is both uninitialised and
+        // not referenced, then we can remove it
+        if (!isSmartPointerType(var->getType()))
+            return false;
+
+        if (!var->hasInit())
+            return true;
+
+        auto cxxConstructExpr = dyn_cast<CXXConstructExpr>(var->getInit());
+        if (!cxxConstructExpr)
+            return false;
+        return
+            cxxConstructExpr->getNumArgs() == 0 || cxxConstructExpr->getArg(0)->isDefaultArgument();
+    }
+
+static Plugin::Registration< UnusedVariableCheck > unusedvariablecheck( "unusedvariablecheck" );
+
+} // namespace
+
+#endif // LO_CLANG_SHARED_PLUGINS
+
+/* vim:set shiftwidth=4 softtabstop=4 expandtab: */