new loplugin unnecessarycatchthrow

Change-Id: Iabab71ee076227bc38447ec109afaea1e53a86a6
Reviewed-on: https://gerrit.libreoffice.org/42643
Tested-by: Jenkins <ci@libreoffice.org>
Reviewed-by: Noel Grandin <noel.grandin@collabora.co.uk>

2 files changed, 114 insertions, 0 deletions

diff --git a/compilerplugins/clang/test/unnecessarycatchthrow.cxx b/compilerplugins/clang/test/unnecessarycatchthrow.cxx
new file mode 100644
index 000000000000..5fb8d83bf9a6
--- /dev/null
+++ b/compilerplugins/clang/test/unnecessarycatchthrow.cxx
@@ -0,0 +1,35 @@
+/* -*- 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 <iostream>
+#include <fstream>
+
+void foo();
+
+int main()
+{
+    try {
+        foo();
+    } catch(int const &) {  // expected-error {{unnecessary catch and throw [loplugin:unnecessarycatchthrow]}}
+        throw;
+    }
+    try {
+        foo();
+    } catch(int const & ex) {  // expected-error {{unnecessary catch and throw [loplugin:unnecessarycatchthrow]}}
+        throw ex;
+    }
+    try {
+        foo();
+    } catch(int const &) {
+        std::cout << "test";
+        throw;
+    }
+};
+
+/* vim:set shiftwidth=4 softtabstop=4 expandtab cinoptions=b1,g0,N-s cinkeys+=0=break: */
diff --git a/compilerplugins/clang/unnecessarycatchthrow.cxx b/compilerplugins/clang/unnecessarycatchthrow.cxx
new file mode 100644
index 000000000000..c69713799a82
--- /dev/null
+++ b/compilerplugins/clang/unnecessarycatchthrow.cxx
@@ -0,0 +1,79 @@
+/* -*- 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 <fstream>
+#include <set>
+
+#include <clang/AST/CXXInheritance.h>
+#include "compat.hxx"
+#include "plugin.hxx"
+
+/**
+look for unnecessary blocks that just catch and rethrow:
+    try {
+       stuff
+    } catch (exception const &) {
+      throw;
+    }
+*/
+
+namespace {
+
+class UnnecessaryCatchThrow:
+    public RecursiveASTVisitor<UnnecessaryCatchThrow>, public loplugin::Plugin
+{
+public:
+    explicit UnnecessaryCatchThrow(InstantiationData const & data): Plugin(data) {}
+
+    virtual void run() override
+    {
+        TraverseDecl(compiler.getASTContext().getTranslationUnitDecl());
+    }
+
+    bool VisitCXXTryStmt(CXXTryStmt const *);
+};
+
+bool UnnecessaryCatchThrow::VisitCXXTryStmt(CXXTryStmt const * tryStmt)
+{
+    if (ignoreLocation(tryStmt))
+        return true;
+    if (tryStmt->getNumHandlers() != 1)
+        return true;
+    auto catchStmt = tryStmt->getHandler(0);
+    auto compoundStmt = dyn_cast<CompoundStmt>(catchStmt->getHandlerBlock());
+    if (!compoundStmt || compoundStmt->size() != 1)
+        return true;
+    auto throwExpr = dyn_cast<CXXThrowExpr>(compoundStmt->body_front());
+    if (!throwExpr)
+        return true;
+    auto subExpr = throwExpr->getSubExpr();
+    if (subExpr)
+    {
+        auto declRefExpr = dyn_cast<DeclRefExpr>(subExpr->IgnoreImpCasts());
+        if (!declRefExpr)
+            return true;
+        if (declRefExpr->getDecl() != catchStmt->getExceptionDecl())
+            return true;
+    }
+
+    report( DiagnosticsEngine::Warning, "unnecessary catch and throw",
+            catchStmt->getLocStart())
+            << catchStmt->getSourceRange();
+    return true;
+}
+
+
+loplugin::Plugin::Registration< UnnecessaryCatchThrow > X("unnecessarycatchthrow");
+
+}
+
+/* vim:set shiftwidth=4 softtabstop=4 expandtab: */