new loplugin to check for static OUStrings

that are better declared as OUStringLiteral

Change-Id: Ifb5d9a12bb31a68641940bec16971a8181a46567
Reviewed-on: https://gerrit.libreoffice.org/27377
Reviewed-by: Noel Grandin <noelgrandin@gmail.com>
Tested-by: Noel Grandin <noelgrandin@gmail.com>

compilerplugins/clang/stringstatic.cxx

@@ -0,0 +1,140 @@
+/* -*- 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 "check.hxx"
+#include "plugin.hxx"
+
+/** Look for static OUString and OUString[], they can be more effeciently declared as:
+
+        static const OUStringLiteral our_aLBEntryMap[] = {
+            OUStringLiteral(" "),
+            OUStringLiteral(", ")};
+        static const OUStringLiteral sName("name");
+
+    which is more efficient at startup time.
+ */
+namespace {
+
+class StringStatic
+    : public clang::RecursiveASTVisitor<StringStatic>
+    , public loplugin::Plugin
+{
+
+public:
+    explicit StringStatic(InstantiationData const& rData) : Plugin(rData) {}
+
+    void run() override;
+    bool VisitVarDecl(VarDecl const*);
+    bool VisitReturnStmt(ReturnStmt const*);
+private:
+    std::set<VarDecl const *> potentialVars;
+    std::set<VarDecl const *> excludeVars;
+};
+
+void StringStatic::run()
+{
+    StringRef fn( compiler.getSourceManager().getFileEntryForID(
+                      compiler.getSourceManager().getMainFileID())->getName() );
+    // passing around pointers to global OUString
+    if (fn.startswith(SRCDIR "/filter/source/svg/"))
+         return;
+    // has a mix of literals and and refs to external OUStrings
+    if (fn == SRCDIR "/ucb/source/ucp/webdav-neon/ContentProperties.cxx")
+         return;
+    // we could use OUStringLiteral1 here, but we'd need to update OUStringLiteral1 to allow BMP chars first
+    if (fn == SRCDIR "/include/chart2/SpecialUnicodes.hxx")
+         return;
+
+    TraverseDecl(compiler.getASTContext().getTranslationUnitDecl());
+
+    for (auto const & pVarDecl : excludeVars) {
+        potentialVars.erase(pVarDecl);
+    }
+    for (auto const & varDecl : potentialVars) {
+        report(DiagnosticsEngine::Warning,
+                "rather declare this using OUStringLiteral or char[]",
+                varDecl->getLocation())
+            << varDecl->getSourceRange();
+    }
+}
+
+bool StringStatic::VisitVarDecl(VarDecl const* varDecl)
+{
+    if (ignoreLocation(varDecl)) {
+        return true;
+    }
+
+    QualType qt = varDecl->getType();
+    if (!varDecl->hasGlobalStorage()
+        || !varDecl->isThisDeclarationADefinition()
+        || !qt.isConstQualified()) {
+        return true;
+    }
+    if (qt->isArrayType()) {
+        qt = qt->getAsArrayTypeUnsafe()->getElementType();
+    }
+    if (!loplugin::TypeCheck(qt).Class("OUString").Namespace("rtl").GlobalNamespace()) {
+        return true;
+    }
+    if (varDecl->hasInit()) {
+        Expr const * expr = varDecl->getInit();
+        while (true) {
+            if (ExprWithCleanups const * exprWithCleanups = dyn_cast<ExprWithCleanups>(expr)) {
+                expr = exprWithCleanups->getSubExpr();
+            }
+            else if (CastExpr const * castExpr = dyn_cast<CastExpr>(expr)) {
+                expr = castExpr->getSubExpr();
+            }
+            else if (MaterializeTemporaryExpr const * materializeExpr = dyn_cast<MaterializeTemporaryExpr>(expr)) {
+                expr = materializeExpr->GetTemporaryExpr();
+            }
+            else if (CXXBindTemporaryExpr const * bindExpr = dyn_cast<CXXBindTemporaryExpr>(expr)) {
+                expr = bindExpr->getSubExpr();
+            }
+            else if (CXXConstructExpr const * constructExpr = dyn_cast<CXXConstructExpr>(expr)) {
+                if (constructExpr->getNumArgs() != 1) {
+                    return true;
+                }
+                expr = constructExpr->getArg(0);
+            } else if (isa<CallExpr>(expr)) {
+                return true;
+            } else {
+                break;
+            }
+        }
+    }
+    potentialVars.insert(varDecl);
+
+    return true;
+}
+
+bool StringStatic::VisitReturnStmt(ReturnStmt const * returnStmt)
+{
+    if (ignoreLocation(returnStmt)) {
+        return true;
+    }
+    if (!returnStmt->getRetValue()) {
+        return true;
+    }
+    DeclRefExpr const * declRef = dyn_cast<DeclRefExpr>(returnStmt->getRetValue());
+    if (!declRef) {
+        return true;
+    }
+    VarDecl const * varDecl = dyn_cast<VarDecl>(declRef->getDecl());
+    if (varDecl) {
+        excludeVars.insert(varDecl);
+    }
+    return true;
+}
+
+loplugin::Plugin::Registration<StringStatic> X("stringstatic");
+
+} // namespace
+
+/* vim:set shiftwidth=4 softtabstop=4 expandtab: */