Adding upstream version 4:24.2.0.upstream/4%24.2.0

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 2259 insertions, 0 deletions

diff --git a/compilerplugins/clang/stringconstant.cxx b/compilerplugins/clang/stringconstant.cxx
new file mode 100644
index 0000000000..c64c2c9d65
--- /dev/null
+++ b/compilerplugins/clang/stringconstant.cxx
@@ -0,0 +1,2259 @@
+/* -*- 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 <algorithm>
+#include <cassert>
+#include <cstdint>
+#include <cstdlib>
+#include <iomanip>
+#include <limits>
+#include <sstream>
+#include <stack>
+#include <string>
+#include <vector>
+#include <iostream>
+
+#include "check.hxx"
+#include "compat.hxx"
+#include "plugin.hxx"
+
+// Define a "string constant" to be a constant expression either of type "array
+// of N char" where each array element is a non-NULL ASCII character---except
+// that the last array element may be NULL, or, in some situations, of type char
+// with an ASCII value (including NULL).  Note that the former includes
+// expressions denoting narrow string literals like "foo", and, with toolchains
+// that support constexpr, constexpr variables declared like
+//
+//   constexpr char str[] = "bar";
+//
+// This plugin flags uses of OUString functions with string constant arguments
+// that can be rewritten more directly, like
+//
+//   OUString::createFromAscii("foo")  ->  "foo"
+//
+// and
+//
+//   s.equals(OUString("bar"))  ->  s == "bar"
+
+namespace {
+
+SourceLocation getMemberLocation(Expr const * expr) {
+    CallExpr const * e1 = dyn_cast<CallExpr>(expr);
+    MemberExpr const * e2 = e1 == nullptr
+        ? nullptr : dyn_cast<MemberExpr>(e1->getCallee());
+    return e2 == nullptr ? expr->getExprLoc()/*TODO*/ : e2->getMemberLoc();
+}
+
+bool isLhsOfAssignment(FunctionDecl const * decl, unsigned parameter) {
+    if (parameter != 0) {
+        return false;
+    }
+    auto oo = decl->getOverloadedOperator();
+    return oo == OO_Equal
+        || (oo >= OO_PlusEqual && oo <= OO_GreaterGreaterEqual);
+}
+
+bool hasOverloads(FunctionDecl const * decl, unsigned arguments) {
+    int n = 0;
+    auto ctx = decl->getDeclContext();
+    if (ctx->getDeclKind() == Decl::LinkageSpec) {
+        ctx = ctx->getParent();
+    }
+    auto res = ctx->lookup(decl->getDeclName());
+    for (auto d = res.begin(); d != res.end(); ++d) {
+        FunctionDecl const * f = dyn_cast<FunctionDecl>(*d);
+        if (f != nullptr && f->getMinRequiredArguments() <= arguments
+            && f->getNumParams() >= arguments)
+        {
+            auto consDecl = dyn_cast<CXXConstructorDecl>(f);
+            if (consDecl && consDecl->isCopyOrMoveConstructor()) {
+                continue;
+            }
+            ++n;
+            if (n == 2) {
+                return true;
+            }
+        }
+    }
+    return false;
+}
+
+CXXConstructExpr const * lookForCXXConstructExpr(Expr const * expr) {
+    if (auto e = dyn_cast<MaterializeTemporaryExpr>(expr)) {
+        expr = e->getSubExpr();
+    }
+    if (auto e = dyn_cast<CXXFunctionalCastExpr>(expr)) {
+        expr = e->getSubExpr();
+    }
+    if (auto e = dyn_cast<CXXBindTemporaryExpr>(expr)) {
+        expr = e->getSubExpr();
+    }
+    if (auto const e = dyn_cast<CXXMemberCallExpr>(expr)) {
+        // Look through OString::operator std::string_view:
+        if (auto const d = dyn_cast_or_null<CXXConversionDecl>(e->getCalleeDecl())) {
+            return lookForCXXConstructExpr(e->getImplicitObjectArgument()->IgnoreParenImpCasts());
+        }
+    }
+    return dyn_cast<CXXConstructExpr>(expr);
+}
+
+char const * adviseNonArray(bool nonArray) {
+    return nonArray
+        ? ", and turn the non-array string constant into an array" : "";
+}
+
+class StringConstant:
+    public loplugin::FilteringRewritePlugin<StringConstant>
+{
+public:
+    explicit StringConstant(loplugin::InstantiationData const & data):
+        FilteringRewritePlugin(data) {}
+
+    void run() override;
+
+    bool TraverseFunctionDecl(FunctionDecl * decl) {
+        returnTypes_.push(decl->getDeclaredReturnType());
+        auto const ret = RecursiveASTVisitor::TraverseFunctionDecl(decl);
+        assert(!returnTypes_.empty());
+        assert(returnTypes_.top() == decl->getDeclaredReturnType());
+        returnTypes_.pop();
+        return ret;
+    }
+
+    bool TraverseCXXDeductionGuideDecl(CXXDeductionGuideDecl * decl) {
+        returnTypes_.push(decl->getDeclaredReturnType());
+        auto const ret = RecursiveASTVisitor::TraverseCXXDeductionGuideDecl(
+            decl);
+        assert(!returnTypes_.empty());
+        assert(returnTypes_.top() == decl->getDeclaredReturnType());
+        returnTypes_.pop();
+        return ret;
+    }
+
+    bool TraverseCXXMethodDecl(CXXMethodDecl * decl) {
+        returnTypes_.push(decl->getDeclaredReturnType());
+        auto const ret = RecursiveASTVisitor::TraverseCXXMethodDecl(decl);
+        assert(!returnTypes_.empty());
+        assert(returnTypes_.top() == decl->getDeclaredReturnType());
+        returnTypes_.pop();
+        return ret;
+    }
+
+    bool TraverseCXXConstructorDecl(CXXConstructorDecl * decl) {
+        returnTypes_.push(decl->getDeclaredReturnType());
+        auto const ret = RecursiveASTVisitor::TraverseCXXConstructorDecl(decl);
+        assert(!returnTypes_.empty());
+        assert(returnTypes_.top() == decl->getDeclaredReturnType());
+        returnTypes_.pop();
+        return ret;
+    }
+
+    bool TraverseCXXDestructorDecl(CXXDestructorDecl * decl) {
+        returnTypes_.push(decl->getDeclaredReturnType());
+        auto const ret = RecursiveASTVisitor::TraverseCXXDestructorDecl(decl);
+        assert(!returnTypes_.empty());
+        assert(returnTypes_.top() == decl->getDeclaredReturnType());
+        returnTypes_.pop();
+        return ret;
+    }
+
+    bool TraverseCXXConversionDecl(CXXConversionDecl * decl) {
+        returnTypes_.push(decl->getDeclaredReturnType());
+        auto const ret = RecursiveASTVisitor::TraverseCXXConversionDecl(decl);
+        assert(!returnTypes_.empty());
+        assert(returnTypes_.top() == decl->getDeclaredReturnType());
+        returnTypes_.pop();
+        return ret;
+    }
+
+    bool TraverseObjCMethodDecl(ObjCMethodDecl * decl) {
+        returnTypes_.push(decl->getReturnType());
+        auto const ret = RecursiveASTVisitor::TraverseObjCMethodDecl(decl);
+        assert(!returnTypes_.empty());
+        assert(returnTypes_.top() == decl->getReturnType());
+        returnTypes_.pop();
+        return ret;
+    }
+
+    bool TraverseCallExpr(CallExpr * expr);
+
+    bool TraverseCXXMemberCallExpr(CXXMemberCallExpr * expr);
+
+    bool TraverseCXXOperatorCallExpr(CXXOperatorCallExpr * expr);
+
+    bool TraverseCXXConstructExpr(CXXConstructExpr * expr);
+
+    bool VisitCallExpr(CallExpr const * expr);
+
+    bool VisitCXXMemberCallExpr(CXXMemberCallExpr const * expr);
+
+    bool VisitCXXConstructExpr(CXXConstructExpr const * expr);
+
+    bool VisitReturnStmt(ReturnStmt const * stmt);
+
+private:
+    enum class ContentKind { Ascii, Utf8, Arbitrary };
+
+    enum class TreatEmpty { DefaultCtor, CheckEmpty, Error };
+
+    enum class ChangeKind { Char, CharLen, SingleChar, OUStringChar };
+
+    enum class PassThrough { No, EmptyConstantString, NonEmptyConstantString };
+
+    std::string describeChangeKind(ChangeKind kind);
+
+    bool isStringConstant(
+        Expr const * expr, unsigned * size, bool * nonArray,
+        ContentKind * content, bool * embeddedNuls, bool * terminatingNul,
+        std::vector<char32_t> * utf8Content = nullptr);
+
+    bool isZero(Expr const * expr);
+
+    void reportChange(
+        Expr const * expr, ChangeKind kind, std::string const & original,
+        std::string const & replacement, PassThrough pass, bool nonArray,
+        char const * rewriteFrom, char const * rewriteTo);
+
+    void checkEmpty(
+        CallExpr const * expr, FunctionDecl const * callee,
+        TreatEmpty treatEmpty, unsigned size, std::string * replacement);
+
+    void handleChar(
+        CallExpr const * expr, unsigned arg, FunctionDecl const * callee,
+        std::string const & replacement, TreatEmpty treatEmpty, bool literal,
+    char const * rewriteFrom = nullptr, char const * rewriteTo = nullptr);
+
+    void handleCharLen(
+        CallExpr const * expr, unsigned arg1, unsigned arg2,
+        FunctionDecl const * callee, std::string const & replacement,
+        TreatEmpty treatEmpty);
+
+    void handleOUStringCtor(
+        CallExpr const * expr, unsigned arg, FunctionDecl const * callee,
+        bool explicitFunctionalCastNotation);
+
+    void handleOStringCtor(
+        CallExpr const * expr, unsigned arg, FunctionDecl const * callee,
+        bool explicitFunctionalCastNotation);
+
+    void handleOUStringCtor(
+        Expr const * expr, Expr const * argExpr, FunctionDecl const * callee,
+        bool explicitFunctionalCastNotation);
+
+    void handleOStringCtor(
+        Expr const * expr, Expr const * argExpr, FunctionDecl const * callee,
+        bool explicitFunctionalCastNotation);
+
+    enum class StringKind { Unicode, Char };
+    void handleStringCtor(
+        Expr const * expr, Expr const * argExpr, FunctionDecl const * callee,
+        bool explicitFunctionalCastNotation, StringKind stringKind);
+
+    void handleFunArgOstring(
+        CallExpr const * expr, unsigned arg, FunctionDecl const * callee);
+
+    std::stack<QualType> returnTypes_;
+    std::stack<Expr const *> calls_;
+};
+
+void StringConstant::run() {
+    if (compiler.getLangOpts().CPlusPlus
+        && compiler.getPreprocessor().getIdentifierInfo(
+            "LIBO_INTERNAL_ONLY")->hasMacroDefinition())
+            //TODO: some parts of it are useful for external code, too
+    {
+        TraverseDecl(compiler.getASTContext().getTranslationUnitDecl());
+    }
+}
+
+bool StringConstant::TraverseCallExpr(CallExpr * expr) {
+    if (!WalkUpFromCallExpr(expr)) {
+        return false;
+    }
+    calls_.push(expr);
+    bool bRes = true;
+    for (auto * e: expr->children()) {
+        if (!TraverseStmt(e)) {
+            bRes = false;
+            break;
+        }
+    }
+    calls_.pop();
+    return bRes;
+}
+
+bool StringConstant::TraverseCXXMemberCallExpr(CXXMemberCallExpr * expr) {
+    if (!WalkUpFromCXXMemberCallExpr(expr)) {
+        return false;
+    }
+    calls_.push(expr);
+    bool bRes = true;
+    for (auto * e: expr->children()) {
+        if (!TraverseStmt(e)) {
+            bRes = false;
+            break;
+        }
+    }
+    calls_.pop();
+    return bRes;
+}
+
+bool StringConstant::TraverseCXXOperatorCallExpr(CXXOperatorCallExpr * expr)
+{
+    if (!WalkUpFromCXXOperatorCallExpr(expr)) {
+        return false;
+    }
+    calls_.push(expr);
+    bool bRes = true;
+    for (auto * e: expr->children()) {
+        if (!TraverseStmt(e)) {
+            bRes = false;
+            break;
+        }
+    }
+    calls_.pop();
+    return bRes;
+}
+
+bool StringConstant::TraverseCXXConstructExpr(CXXConstructExpr * expr) {
+    if (!WalkUpFromCXXConstructExpr(expr)) {
+        return false;
+    }
+    calls_.push(expr);
+    bool bRes = true;
+    for (auto * e: expr->children()) {
+        if (!TraverseStmt(e)) {
+            bRes = false;
+            break;
+        }
+    }
+    calls_.pop();
+    return bRes;
+}
+
+bool StringConstant::VisitCallExpr(CallExpr const * expr) {
+    if (ignoreLocation(expr)) {
+        return true;
+    }
+    FunctionDecl const * fdecl = expr->getDirectCallee();
+    if (fdecl == nullptr) {
+        return true;
+    }
+    for (unsigned i = 0; i != fdecl->getNumParams(); ++i) {
+        auto t = fdecl->getParamDecl(i)->getType();
+        if (loplugin::TypeCheck(t).NotSubstTemplateTypeParmType()
+            .LvalueReference().Const().NotSubstTemplateTypeParmType()
+            .Class("OUString").Namespace("rtl").GlobalNamespace())
+        {
+            if (!(isLhsOfAssignment(fdecl, i)
+                  || hasOverloads(fdecl, expr->getNumArgs())))
+            {
+                handleOUStringCtor(expr, i, fdecl, true);
+            }
+        }
+        if (loplugin::TypeCheck(t).NotSubstTemplateTypeParmType()
+            .LvalueReference().Const().NotSubstTemplateTypeParmType()
+            .Class("OString").Namespace("rtl").GlobalNamespace())
+        {
+            if (!(isLhsOfAssignment(fdecl, i)
+                  || hasOverloads(fdecl, expr->getNumArgs())))
+            {
+                handleOStringCtor(expr, i, fdecl, true);
+            }
+        }
+    }
+    loplugin::DeclCheck dc(fdecl);
+    //TODO: u.compareToAscii("foo") -> u.???("foo")
+    //TODO: u.compareToIgnoreAsciiCaseAscii("foo") -> u.???("foo")
+    if ((dc.Function("createFromAscii").Class("OUString").Namespace("rtl")
+         .GlobalNamespace())
+        && fdecl->getNumParams() == 1)
+    {
+        // OUString::createFromAscii("foo") -> OUString("foo")
+        handleChar(
+            expr, 0, fdecl, "rtl::OUString constructor",
+            TreatEmpty::DefaultCtor, true);
+        return true;
+    }
+    if ((dc.Function("endsWithAsciiL").Class("OUString").Namespace("rtl")
+         .GlobalNamespace())
+        && fdecl->getNumParams() == 2)
+    {
+        // u.endsWithAsciiL("foo", 3) -> u.endsWith("foo"):
+        handleCharLen(
+            expr, 0, 1, fdecl, "rtl::OUString::endsWith", TreatEmpty::Error);
+        return true;
+    }
+    if ((dc.Function("endsWithIgnoreAsciiCaseAsciiL").Class("OUString")
+         .Namespace("rtl").GlobalNamespace())
+        && fdecl->getNumParams() == 2)
+    {
+        // u.endsWithIgnoreAsciiCaseAsciiL("foo", 3) ->
+        // u.endsWithIgnoreAsciiCase("foo"):
+        handleCharLen(
+            expr, 0, 1, fdecl, "rtl::OUString::endsWithIgnoreAsciiCase",
+            TreatEmpty::Error);
+        return true;
+    }
+    if ((dc.Function("equalsAscii").Class("OUString").Namespace("rtl")
+         .GlobalNamespace())
+        && fdecl->getNumParams() == 1)
+    {
+        // u.equalsAscii("foo") -> u == "foo":
+        handleChar(
+            expr, 0, fdecl, "operator ==", TreatEmpty::CheckEmpty, false);
+        return true;
+    }
+    if ((dc.Function("equalsAsciiL").Class("OUString").Namespace("rtl")
+         .GlobalNamespace())
+        && fdecl->getNumParams() == 2)
+    {
+        // u.equalsAsciiL("foo", 3) -> u == "foo":
+        handleCharLen(expr, 0, 1, fdecl, "operator ==", TreatEmpty::CheckEmpty);
+        return true;
+    }
+    if ((dc.Function("equalsIgnoreAsciiCaseAscii").Class("OUString")
+         .Namespace("rtl").GlobalNamespace())
+        && fdecl->getNumParams() == 1)
+    {
+        // u.equalsIgnoreAsciiCaseAscii("foo") ->
+        // u.equalsIngoreAsciiCase("foo"):
+
+        auto file = getFilenameOfLocation(
+            compiler.getSourceManager().getSpellingLoc(expr->getBeginLoc()));
+        if (loplugin::isSamePathname(
+                file, SRCDIR "/sal/qa/rtl/strings/test_oustring_compare.cxx"))
+        {
+            return true;
+        }
+        handleChar(
+            expr, 0, fdecl, "rtl::OUString::equalsIgnoreAsciiCase",
+            TreatEmpty::CheckEmpty, false);
+        return true;
+    }
+    if ((dc.Function("equalsIgnoreAsciiCaseAsciiL").Class("OUString")
+         .Namespace("rtl").GlobalNamespace())
+        && fdecl->getNumParams() == 2)
+    {
+        // u.equalsIgnoreAsciiCaseAsciiL("foo", 3) ->
+        // u.equalsIngoreAsciiCase("foo"):
+        auto file = getFilenameOfLocation(
+            compiler.getSourceManager().getSpellingLoc(expr->getBeginLoc()));
+        if (loplugin::isSamePathname(
+                file, SRCDIR "/sal/qa/rtl/strings/test_oustring_compare.cxx"))
+        {
+            return true;
+        }
+        handleCharLen(
+            expr, 0, 1, fdecl, "rtl::OUString::equalsIgnoreAsciiCase",
+            TreatEmpty::CheckEmpty);
+        return true;
+    }
+    if ((dc.Function("indexOfAsciiL").Class("OUString").Namespace("rtl")
+         .GlobalNamespace())
+        && fdecl->getNumParams() == 3)
+    {
+        assert(expr->getNumArgs() == 3);
+        // u.indexOfAsciiL("foo", 3, i) -> u.indexOf("foo", i):
+        handleCharLen(
+            expr, 0, 1, fdecl, "rtl::OUString::indexOf", TreatEmpty::Error);
+        return true;
+    }
+    if ((dc.Function("lastIndexOfAsciiL").Class("OUString").Namespace("rtl")
+         .GlobalNamespace())
+        && fdecl->getNumParams() == 2)
+    {
+        // u.lastIndexOfAsciiL("foo", 3) -> u.lastIndexOf("foo"):
+        handleCharLen(
+            expr, 0, 1, fdecl, "rtl::OUString::lastIndexOf", TreatEmpty::Error);
+        return true;
+    }
+    if ((dc.Function("matchAsciiL").Class("OUString").Namespace("rtl")
+         .GlobalNamespace())
+        && fdecl->getNumParams() == 3)
+    {
+        assert(expr->getNumArgs() == 3);
+        // u.matchAsciiL("foo", 3, i) -> u.match("foo", i):
+        handleCharLen(
+            expr, 0, 1, fdecl,
+            (isZero(expr->getArg(2))
+             ? std::string("rtl::OUString::startsWith")
+             : std::string("rtl::OUString::match")),
+            TreatEmpty::Error);
+        return true;
+    }
+    if ((dc.Function("matchIgnoreAsciiCaseAsciiL").Class("OUString")
+         .Namespace("rtl").GlobalNamespace())
+        && fdecl->getNumParams() == 3)
+    {
+        assert(expr->getNumArgs() == 3);
+        // u.matchIgnoreAsciiCaseAsciiL("foo", 3, i) ->
+        // u.matchIgnoreAsciiCase("foo", i):
+        handleCharLen(
+            expr, 0, 1, fdecl,
+            (isZero(expr->getArg(2))
+             ? std::string("rtl::OUString::startsWithIgnoreAsciiCase")
+             : std::string("rtl::OUString::matchIgnoreAsciiCase")),
+            TreatEmpty::Error);
+        return true;
+    }
+    if ((dc.Function("reverseCompareToAsciiL").Class("OUString")
+         .Namespace("rtl").GlobalNamespace())
+        && fdecl->getNumParams() == 2)
+    {
+        // u.reverseCompareToAsciiL("foo", 3) -> u.reverseCompareTo("foo"):
+        handleCharLen(
+            expr, 0, 1, fdecl, "rtl::OUString::reverseCompareTo",
+            TreatEmpty::Error);
+        return true;
+    }
+    if ((dc.Function("reverseCompareTo").Class("OUString").Namespace("rtl")
+         .GlobalNamespace())
+        && fdecl->getNumParams() == 1)
+    {
+        handleOUStringCtor(expr, 0, fdecl, false);
+        return true;
+    }
+    if ((dc.Function("equalsIgnoreAsciiCase").Class("OUString").Namespace("rtl")
+         .GlobalNamespace())
+        && fdecl->getNumParams() == 1)
+    {
+        handleOUStringCtor(expr, 0, fdecl, false);
+        return true;
+    }
+    if ((dc.Function("match").Class("OUString").Namespace("rtl")
+         .GlobalNamespace())
+        && fdecl->getNumParams() == 2)
+    {
+        handleOUStringCtor(expr, 0, fdecl, false);
+        return true;
+    }
+    if ((dc.Function("matchIgnoreAsciiCase").Class("OUString").Namespace("rtl")
+         .GlobalNamespace())
+        && fdecl->getNumParams() == 2)
+    {
+        handleOUStringCtor(expr, 0, fdecl, false);
+        return true;
+    }
+    if ((dc.Function("startsWith").Class("OUString").Namespace("rtl")
+         .GlobalNamespace())
+        && fdecl->getNumParams() == 2)
+    {
+        handleOUStringCtor(expr, 0, fdecl, false);
+        return true;
+    }
+    if ((dc.Function("startsWithIgnoreAsciiCase").Class("OUString")
+         .Namespace("rtl").GlobalNamespace())
+        && fdecl->getNumParams() == 2)
+    {
+        handleOUStringCtor(expr, 0, fdecl, false);
+        return true;
+    }
+    if ((dc.Function("endsWith").Class("OUString").Namespace("rtl")
+         .GlobalNamespace())
+        && fdecl->getNumParams() == 2)
+    {
+        handleOUStringCtor(expr, 0, fdecl, false);
+        return true;
+    }
+    if ((dc.Function("endsWithIgnoreAsciiCase").Class("OUString")
+         .Namespace("rtl").GlobalNamespace())
+        && fdecl->getNumParams() == 2)
+    {
+        handleOUStringCtor(expr, 0, fdecl, false);
+        return true;
+    }
+    if ((dc.Function("indexOf").Class("OUString").Namespace("rtl")
+         .GlobalNamespace())
+        && fdecl->getNumParams() == 2)
+    {
+        handleOUStringCtor(expr, 0, fdecl, false);
+        return true;
+    }
+    if ((dc.Function("lastIndexOf").Class("OUString").Namespace("rtl")
+         .GlobalNamespace())
+        && fdecl->getNumParams() == 1)
+    {
+        handleOUStringCtor(expr, 0, fdecl, false);
+        return true;
+    }
+    if ((dc.Function("replaceFirst").Class("OUString").Namespace("rtl")
+         .GlobalNamespace())
+        && fdecl->getNumParams() == 3)
+    {
+        handleOUStringCtor(expr, 0, fdecl, false);
+        handleOUStringCtor(expr, 1, fdecl, false);
+        return true;
+    }
+    if ((dc.Function("replaceAll").Class("OUString").Namespace("rtl")
+         .GlobalNamespace())
+        && (fdecl->getNumParams() == 2 || fdecl->getNumParams() == 3))
+    {
+        handleOUStringCtor(expr, 0, fdecl, false);
+        handleOUStringCtor(expr, 1, fdecl, false);
+        return true;
+    }
+    if ((dc.Operator(OO_PlusEqual).Class("OUString").Namespace("rtl")
+         .GlobalNamespace())
+        && fdecl->getNumParams() == 1)
+    {
+        handleOUStringCtor(
+            expr, dyn_cast<CXXOperatorCallExpr>(expr) == nullptr ? 0 : 1,
+            fdecl, false);
+        return true;
+    }
+    if ((dc.Function("equals").Class("OUString").Namespace("rtl")
+         .GlobalNamespace())
+        && fdecl->getNumParams() == 1)
+    {
+        unsigned n;
+        bool nonArray;
+        ContentKind cont;
+        bool emb;
+        bool trm;
+        if (!isStringConstant(
+                expr->getArg(0)->IgnoreParenImpCasts(), &n, &nonArray, &cont,
+                &emb, &trm))
+        {
+            return true;
+        }
+        if (cont != ContentKind::Ascii) {
+            report(
+                DiagnosticsEngine::Warning,
+                ("call of '%0' with string constant argument containing"
+                 " non-ASCII characters"),
+                expr->getExprLoc())
+                << fdecl->getQualifiedNameAsString() << expr->getSourceRange();
+        }
+        if (emb) {
+            report(
+                DiagnosticsEngine::Warning,
+                ("call of '%0' with string constant argument containing"
+                 " embedded NULLs"),
+                expr->getExprLoc())
+                << fdecl->getQualifiedNameAsString() << expr->getSourceRange();
+        }
+        if (n == 0) {
+            report(
+                DiagnosticsEngine::Warning,
+                ("rewrite call of '%0' with empty string constant argument as"
+                 " call of 'rtl::OUString::isEmpty'"),
+                expr->getExprLoc())
+                << fdecl->getQualifiedNameAsString() << expr->getSourceRange();
+            return true;
+        }
+    }
+    if (dc.Operator(OO_EqualEqual).Namespace("rtl").GlobalNamespace()
+        && fdecl->getNumParams() == 2)
+    {
+        for (unsigned i = 0; i != 2; ++i) {
+            unsigned n;
+            bool nonArray;
+            ContentKind cont;
+            bool emb;
+            bool trm;
+            if (!isStringConstant(
+                    expr->getArg(i)->IgnoreParenImpCasts(), &n, &nonArray,
+                    &cont, &emb, &trm))
+            {
+                continue;
+            }
+            if (cont != ContentKind::Ascii) {
+                report(
+                    DiagnosticsEngine::Warning,
+                    ("call of '%0' with string constant argument containing"
+                     " non-ASCII characters"),
+                    expr->getExprLoc())
+                    << fdecl->getQualifiedNameAsString()
+                    << expr->getSourceRange();
+            }
+            if (emb) {
+                report(
+                    DiagnosticsEngine::Warning,
+                    ("call of '%0' with string constant argument containing"
+                     " embedded NULLs"),
+                    expr->getExprLoc())
+                    << fdecl->getQualifiedNameAsString()
+                    << expr->getSourceRange();
+            }
+            if (n == 0) {
+                report(
+                    DiagnosticsEngine::Warning,
+                    ("rewrite call of '%0' with empty string constant argument"
+                     " as call of 'rtl::OUString::isEmpty'"),
+                    expr->getExprLoc())
+                    << fdecl->getQualifiedNameAsString()
+                    << expr->getSourceRange();
+            }
+        }
+        return true;
+    }
+    if (dc.Operator(OO_ExclaimEqual).Namespace("rtl").GlobalNamespace()
+        && fdecl->getNumParams() == 2)
+    {
+        for (unsigned i = 0; i != 2; ++i) {
+            unsigned n;
+            bool nonArray;
+            ContentKind cont;
+            bool emb;
+            bool trm;
+            if (!isStringConstant(
+                    expr->getArg(i)->IgnoreParenImpCasts(), &n, &nonArray,
+                    &cont, &emb, &trm))
+            {
+                continue;
+            }
+            if (cont != ContentKind::Ascii) {
+                report(
+                    DiagnosticsEngine::Warning,
+                    ("call of '%0' with string constant argument containing"
+                     " non-ASCII characters"),
+                    expr->getExprLoc())
+                    << fdecl->getQualifiedNameAsString()
+                    << expr->getSourceRange();
+            }
+            if (emb) {
+                report(
+                    DiagnosticsEngine::Warning,
+                    ("call of '%0' with string constant argument containing"
+                     " embedded NULLs"),
+                    expr->getExprLoc())
+                    << fdecl->getQualifiedNameAsString()
+                    << expr->getSourceRange();
+            }
+            if (n == 0) {
+                report(
+                    DiagnosticsEngine::Warning,
+                    ("rewrite call of '%0' with empty string constant argument"
+                     " as call of '!rtl::OUString::isEmpty'"),
+                    expr->getExprLoc())
+                    << fdecl->getQualifiedNameAsString()
+                    << expr->getSourceRange();
+            }
+        }
+        return true;
+    }
+    if (dc.Operator(OO_Equal).Namespace("rtl").GlobalNamespace()
+        && fdecl->getNumParams() == 1)
+    {
+        unsigned n;
+        bool nonArray;
+        ContentKind cont;
+        bool emb;
+        bool trm;
+        if (!isStringConstant(
+                expr->getArg(1)->IgnoreParenImpCasts(), &n, &nonArray, &cont,
+                &emb, &trm))
+        {
+            return true;
+        }
+        if (cont != ContentKind::Ascii) {
+            report(
+                DiagnosticsEngine::Warning,
+                ("call of '%0' with string constant argument containing"
+                 " non-ASCII characters"),
+                expr->getExprLoc())
+                << fdecl->getQualifiedNameAsString() << expr->getSourceRange();
+        }
+        if (emb) {
+            report(
+                DiagnosticsEngine::Warning,
+                ("call of '%0' with string constant argument containing"
+                 " embedded NULLs"),
+                expr->getExprLoc())
+                << fdecl->getQualifiedNameAsString() << expr->getSourceRange();
+        }
+        if (n == 0) {
+            report(
+                DiagnosticsEngine::Warning,
+                ("rewrite call of '%0' with empty string constant argument as"
+                 " call of 'rtl::OUString::clear'"),
+                expr->getExprLoc())
+                << fdecl->getQualifiedNameAsString() << expr->getSourceRange();
+            return true;
+        }
+        return true;
+    }
+    if (dc.Function("append").Class("OUStringBuffer").Namespace("rtl").GlobalNamespace()
+        && fdecl->getNumParams() == 1)
+    {
+        handleChar(expr, 0, fdecl, "", TreatEmpty::Error, false);
+        return true;
+    }
+    if ((dc.Function("appendAscii").Class("OUStringBuffer").Namespace("rtl")
+         .GlobalNamespace())
+        && fdecl->getNumParams() == 1)
+    {
+        // u.appendAscii("foo") -> u.append("foo")
+        handleChar(
+            expr, 0, fdecl, "rtl::OUStringBuffer::append", TreatEmpty::Error,
+            true, "appendAscii", "append");
+        return true;
+    }
+    if ((dc.Function("appendAscii").Class("OUStringBuffer").Namespace("rtl")
+         .GlobalNamespace())
+        && fdecl->getNumParams() == 2)
+    {
+        // u.appendAscii("foo", 3) -> u.append("foo"):
+        handleCharLen(
+            expr, 0, 1, fdecl, "rtl::OUStringBuffer::append",
+            TreatEmpty::Error);
+        return true;
+    }
+    if (dc.Function("append").Class("OStringBuffer").Namespace("rtl")
+        .GlobalNamespace())
+    {
+        switch (fdecl->getNumParams()) {
+        case 1:
+            handleFunArgOstring(expr, 0, fdecl);
+            break;
+        case 2:
+            {
+                // b.append("foo", 3) -> b.append("foo"):
+                auto file = getFilenameOfLocation(
+                    compiler.getSourceManager().getSpellingLoc(
+                        expr->getBeginLoc()));
+                if (loplugin::isSamePathname(
+                        file,
+                        SRCDIR "/sal/qa/OStringBuffer/rtl_OStringBuffer.cxx"))
+                {
+                    return true;
+                }
+                handleCharLen(
+                    expr, 0, 1, fdecl, "rtl::OStringBuffer::append",
+                    TreatEmpty::Error);
+            }
+            break;
+        default:
+            break;
+        }
+        return true;
+    }
+    if (dc.Function("insert").Class("OStringBuffer").Namespace("rtl")
+        .GlobalNamespace())
+    {
+        switch (fdecl->getNumParams()) {
+        case 2:
+            handleFunArgOstring(expr, 1, fdecl);
+            break;
+        case 3:
+            {
+                // b.insert(i, "foo", 3) -> b.insert(i, "foo"):
+                handleCharLen(
+                    expr, 1, 2, fdecl, "rtl::OStringBuffer::insert",
+                    TreatEmpty::Error);
+                break;
+            }
+        default:
+            break;
+        }
+        return true;
+    }
+    return true;
+}
+
+bool StringConstant::VisitCXXMemberCallExpr(CXXMemberCallExpr const * expr) {
+    if (ignoreLocation(expr)) {
+        return true;
+    }
+    FunctionDecl const * fdecl = expr->getDirectCallee();
+    if (fdecl == nullptr) {
+        return true;
+    }
+    auto const c = loplugin::DeclCheck(fdecl).Function("getStr");
+    if ((c.Class("OString").Namespace("rtl").GlobalNamespace()
+         || c.Class("OUString").Namespace("rtl").GlobalNamespace())
+        && fdecl->getNumParams() == 0)
+    {
+        auto const e1 = expr->getImplicitObjectArgument()->IgnoreImplicit()->IgnoreParens();
+        if (auto const e2 = dyn_cast<CXXTemporaryObjectExpr>(e1)) {
+            if (e2->getNumArgs() != 0) {
+                return true;
+            }
+            report(
+                DiagnosticsEngine::Warning,
+                "in call of '%0', replace default-constructed %1 directly with an empty %select{ordinary|UTF-16}2 string literal",
+                expr->getExprLoc())
+                << fdecl->getQualifiedNameAsString() << e2->getType() << bool(loplugin::TypeCheck(e2->getType()).Class("OUString")) << expr->getSourceRange();
+            return true;
+        }
+        if (auto const e2 = dyn_cast<CXXFunctionalCastExpr>(e1)) {
+            auto const e3 = dyn_cast<clang::StringLiteral>(e2->getSubExprAsWritten()->IgnoreParens());
+            if (e3 == nullptr) {
+                return true;
+            }
+            report(
+                DiagnosticsEngine::Warning,
+                "in call of '%0', replace %1 constructed from a string literal directly with %select{the|a UTF-16}2 string literal",
+                expr->getExprLoc())
+                << fdecl->getQualifiedNameAsString() << e2->getType() << (loplugin::TypeCheck(e2->getType()).Class("OUString") && !e3->isUTF16()) << expr->getSourceRange();
+            return true;
+        }
+    }
+    return true;
+}
+
+bool StringConstant::VisitCXXConstructExpr(CXXConstructExpr const * expr) {
+    if (ignoreLocation(expr)) {
+        return true;
+    }
+    auto classdecl = expr->getConstructor()->getParent();
+    if (loplugin::DeclCheck(classdecl)
+        .Class("OUString").Namespace("rtl").GlobalNamespace())
+    {
+        ChangeKind kind;
+        PassThrough pass;
+        bool simplify;
+        switch (expr->getConstructor()->getNumParams()) {
+        case 1:
+            if (!loplugin::TypeCheck(
+                    expr->getConstructor()->getParamDecl(0)->getType())
+                .Typedef("sal_Unicode").GlobalNamespace())
+            {
+                return true;
+            }
+            kind = ChangeKind::SingleChar;
+            pass = PassThrough::NonEmptyConstantString;
+            simplify = false;
+            break;
+        case 2:
+            {
+                auto arg = expr->getArg(0);
+                if (loplugin::TypeCheck(arg->getType())
+                    .Class("OUStringChar_").Namespace("rtl")
+                    .GlobalNamespace())
+                {
+                    kind = ChangeKind::OUStringChar;
+                    pass = PassThrough::NonEmptyConstantString;
+                    simplify = false;
+                } else {
+                    unsigned n;
+                    bool nonArray;
+                    ContentKind cont;
+                    bool emb;
+                    bool trm;
+                    if (!isStringConstant(
+                            arg->IgnoreParenImpCasts(), &n, &nonArray, &cont,
+                            &emb, &trm))
+                    {
+                        return true;
+                    }
+                    if (cont != ContentKind::Ascii) {
+                        report(
+                            DiagnosticsEngine::Warning,
+                            ("construction of %0 with string constant argument"
+                             " containing non-ASCII characters"),
+                            expr->getExprLoc())
+                            << classdecl << expr->getSourceRange();
+                    }
+                    if (emb) {
+                        report(
+                            DiagnosticsEngine::Warning,
+                            ("construction of %0 with string constant argument"
+                             " containing embedded NULLs"),
+                            expr->getExprLoc())
+                            << classdecl << expr->getSourceRange();
+                    }
+                    kind = ChangeKind::Char;
+                    pass = n == 0
+                        ? PassThrough::EmptyConstantString
+                        : PassThrough::NonEmptyConstantString;
+                    simplify = false;
+                }
+                break;
+            }
+        case 4:
+            {
+                unsigned n;
+                bool nonArray;
+                ContentKind cont;
+                bool emb;
+                bool trm;
+                std::vector<char32_t> utf8Cont;
+                if (!isStringConstant(
+                        expr->getArg(0)->IgnoreParenImpCasts(), &n, &nonArray,
+                        &cont, &emb, &trm, &utf8Cont))
+                {
+                    return true;
+                }
+                APSInt res;
+                if (!compat::EvaluateAsInt(expr->getArg(1),
+                        res, compiler.getASTContext()))
+                {
+                    return true;
+                }
+                if (res != n) {
+                    report(
+                        DiagnosticsEngine::Warning,
+                        ("suspicious 'rtl::OUString' constructor with literal"
+                         " of length %0 and non-matching length argument %1"),
+                        expr->getExprLoc())
+                        << n << compat::toString(res, 10) << expr->getSourceRange();
+                    return true;
+                }
+                APSInt enc;
+                if (!compat::EvaluateAsInt(expr->getArg(2),
+                        enc, compiler.getASTContext()))
+                {
+                    return true;
+                }
+                auto const encIsAscii = enc == 11; // RTL_TEXTENCODING_ASCII_US
+                auto const encIsUtf8 = enc == 76; // RTL_TEXTENCODING_UTF8
+                if (!compat::EvaluateAsInt(expr->getArg(3),
+                        res, compiler.getASTContext())
+                    || res != 0x333) // OSTRING_TO_OUSTRING_CVTFLAGS
+                {
+                    return true;
+                }
+                if (!encIsAscii && cont == ContentKind::Ascii) {
+                    report(
+                        DiagnosticsEngine::Warning,
+                        ("suspicious 'rtl::OUString' constructor with text"
+                         " encoding %0 but plain ASCII content; use"
+                         " 'RTL_TEXTENCODING_ASCII_US' instead"),
+                        expr->getArg(2)->getExprLoc())
+                        << compat::toString(enc, 10) << expr->getSourceRange();
+                    return true;
+                }
+                if (encIsUtf8) {
+                    if (cont == ContentKind::Arbitrary) {
+                        report(
+                            DiagnosticsEngine::Warning,
+                            ("suspicious 'rtl::OUString' constructor with text"
+                             " encoding 'RTL_TEXTENCODING_UTF8' but non-UTF-8"
+                             " content"),
+                            expr->getArg(0)->getExprLoc())
+                            << expr->getSourceRange();
+                    } else {
+                        assert(cont == ContentKind::Utf8);
+                        //TODO: keep original content as much as possible
+                        std::ostringstream s;
+                        for (auto const c: utf8Cont) {
+                            if (c == '\\') {
+                                s << "\\\\";
+                            } else if (c == '"') {
+                                s << "\\\"";
+                            } else if (c == '\a') {
+                                s << "\\a";
+                            } else if (c == '\b') {
+                                s << "\\b";
+                            } else if (c == '\f') {
+                                s << "\\f";
+                            } else if (c == '\n') {
+                                s << "\\n";
+                            } else if (c == '\r') {
+                                s << "\\r";
+                            } else if (c == '\t') {
+                                s << "\\r";
+                            } else if (c == '\v') {
+                                s << "\\v";
+                            } else if (c <= 0x1F || c == 0x7F) {
+                                s << "\\x" << std::oct << std::setw(3)
+                                  << std::setfill('0')
+                                  << static_cast<std::uint_least32_t>(c);
+                            } else if (c < 0x7F) {
+                                s << char(c);
+                            } else if (c <= 0xFFFF) {
+                                s << "\\u" << std::hex << std::uppercase
+                                  << std::setw(4) << std::setfill('0')
+                                  << static_cast<std::uint_least32_t>(c);
+                            } else {
+                                assert(c <= 0x10FFFF);
+                                s << "\\U" << std::hex << std::uppercase
+                                  << std::setw(8) << std::setfill('0')
+                                  << static_cast<std::uint_least32_t>(c);
+                            }
+                        }
+                        report(
+                            DiagnosticsEngine::Warning,
+                            ("simplify construction of %0 with UTF-8 content as"
+                             " OUString(u\"%1\")"),
+                            expr->getExprLoc())
+                            << classdecl << s.str() << expr->getSourceRange();
+
+                    }
+                    return true;
+                }
+                if (cont != ContentKind::Ascii || emb) {
+                    // cf. remaining uses of RTL_CONSTASCII_USTRINGPARAM
+                    return true;
+                }
+                kind = ChangeKind::Char;
+                pass = n == 0
+                    ? PassThrough::EmptyConstantString
+                    : PassThrough::NonEmptyConstantString;
+                simplify = true;
+                break;
+            }
+        default:
+            return true;
+        }
+        if (!calls_.empty()) {
+            Expr const * call = calls_.top();
+            CallExpr::const_arg_iterator argsBeg;
+            CallExpr::const_arg_iterator argsEnd;
+            if (isa<CallExpr>(call)) {
+                argsBeg = cast<CallExpr>(call)->arg_begin();
+                argsEnd = cast<CallExpr>(call)->arg_end();
+            } else if (isa<CXXConstructExpr>(call)) {
+                argsBeg = cast<CXXConstructExpr>(call)->arg_begin();
+                argsEnd = cast<CXXConstructExpr>(call)->arg_end();
+            } else {
+                assert(false);
+            }
+            for (auto i(argsBeg); i != argsEnd; ++i) {
+                Expr const * e = (*i)->IgnoreParenImpCasts();
+                if (isa<MaterializeTemporaryExpr>(e)) {
+                    e = cast<MaterializeTemporaryExpr>(e)->getSubExpr()
+                        ->IgnoreParenImpCasts();
+                }
+                if (isa<CXXFunctionalCastExpr>(e)) {
+                    e = cast<CXXFunctionalCastExpr>(e)->getSubExpr()
+                        ->IgnoreParenImpCasts();
+                }
+                if (isa<CXXBindTemporaryExpr>(e)) {
+                    e = cast<CXXBindTemporaryExpr>(e)->getSubExpr()
+                        ->IgnoreParenImpCasts();
+                }
+                if (e == expr) {
+                    if (isa<CallExpr>(call)) {
+                        FunctionDecl const * fdecl
+                            = cast<CallExpr>(call)->getDirectCallee();
+                        if (fdecl == nullptr) {
+                            break;
+                        }
+                        loplugin::DeclCheck dc(fdecl);
+                        if (pass == PassThrough::EmptyConstantString) {
+                            if ((dc.Function("equals").Class("OUString")
+                                 .Namespace("rtl").GlobalNamespace())
+                                || (dc.Operator(OO_EqualEqual).Namespace("rtl")
+                                    .GlobalNamespace()))
+                            {
+                                report(
+                                    DiagnosticsEngine::Warning,
+                                    ("rewrite call of '%0' with construction of"
+                                     " %1 with empty string constant argument"
+                                     " as call of 'rtl::OUString::isEmpty'"),
+                                    getMemberLocation(call))
+                                    << fdecl->getQualifiedNameAsString()
+                                    << classdecl << call->getSourceRange();
+                                return true;
+                            }
+                            if (dc.Operator(OO_ExclaimEqual).Namespace("rtl")
+                                    .GlobalNamespace())
+                            {
+                                report(
+                                    DiagnosticsEngine::Warning,
+                                    ("rewrite call of '%0' with construction of"
+                                     " %1 with empty string constant argument"
+                                     " as call of '!rtl::OUString::isEmpty'"),
+                                    getMemberLocation(call))
+                                    << fdecl->getQualifiedNameAsString()
+                                    << classdecl << call->getSourceRange();
+                                return true;
+                            }
+                            if ((dc.Operator(OO_Plus).Namespace("rtl")
+                                    .GlobalNamespace())
+                                || (dc.Operator(OO_Plus).Class("OUString")
+                                    .Namespace("rtl").GlobalNamespace()))
+                            {
+                                report(
+                                    DiagnosticsEngine::Warning,
+                                    ("call of '%0' with suspicious construction"
+                                     " of %1 with empty string constant"
+                                     " argument"),
+                                    getMemberLocation(call))
+                                    << fdecl->getQualifiedNameAsString()
+                                    << classdecl << call->getSourceRange();
+                                return true;
+                            }
+                            if (dc.Operator(OO_Equal).Class("OUString")
+                                .Namespace("rtl").GlobalNamespace())
+                            {
+                                report(
+                                    DiagnosticsEngine::Warning,
+                                    ("rewrite call of '%0' with construction of"
+                                     " %1 with empty string constant argument"
+                                     " as call of 'rtl::OUString::clear'"),
+                                    getMemberLocation(call))
+                                    << fdecl->getQualifiedNameAsString()
+                                    << classdecl << call->getSourceRange();
+                                return true;
+                            }
+                        } else {
+                            assert(pass == PassThrough::NonEmptyConstantString);
+                            if (dc.Function("equals").Class("OUString")
+                                .Namespace("rtl").GlobalNamespace())
+                            {
+                                report(
+                                    DiagnosticsEngine::Warning,
+                                    ("rewrite call of '%0' with construction of"
+                                     " %1 with %2 as 'operator =='"),
+                                    getMemberLocation(call))
+                                    << fdecl->getQualifiedNameAsString()
+                                    << classdecl << describeChangeKind(kind)
+                                    << call->getSourceRange();
+                                return true;
+                            }
+                            if ((dc.Operator(OO_Plus).Namespace("rtl")
+                                    .GlobalNamespace())
+                                || (dc.Operator(OO_Plus).Class("OUString")
+                                    .Namespace("rtl").GlobalNamespace())
+                                || (dc.Operator(OO_EqualEqual).Namespace("rtl")
+                                    .GlobalNamespace())
+                                || (dc.Operator(OO_ExclaimEqual)
+                                    .Namespace("rtl").GlobalNamespace()))
+                            {
+                                if (dc.Operator(OO_Plus).Namespace("rtl")
+                                    .GlobalNamespace())
+                                {
+                                    auto file = getFilenameOfLocation(
+                                            compiler.getSourceManager()
+                                            .getSpellingLoc(
+                                                expr->getBeginLoc()));
+                                    if (loplugin::isSamePathname(
+                                            file,
+                                            (SRCDIR
+                                             "/sal/qa/rtl/strings/test_ostring_concat.cxx"))
+                                        || loplugin::isSamePathname(
+                                            file,
+                                            (SRCDIR
+                                             "/sal/qa/rtl/strings/test_oustring_concat.cxx")))
+                                    {
+                                        return true;
+                                    }
+                                }
+                                auto loc = expr->getArg(0)->getBeginLoc();
+                                while (compiler.getSourceManager()
+                                       .isMacroArgExpansion(loc))
+                                {
+                                    loc = compiler.getSourceManager()
+                                        .getImmediateMacroCallerLoc(loc);
+                                }
+                                if (kind == ChangeKind::SingleChar) {
+                                    report(
+                                        DiagnosticsEngine::Warning,
+                                        ("rewrite construction of %0 with %1 in"
+                                         " call of '%2' as construction of"
+                                         " 'OUStringChar'"),
+                                        getMemberLocation(expr))
+                                        << classdecl << describeChangeKind(kind)
+                                        << fdecl->getQualifiedNameAsString()
+                                        << expr->getSourceRange();
+                                } else {
+                                    report(
+                                        DiagnosticsEngine::Warning,
+                                        ("elide construction of %0 with %1 in"
+                                         " call of '%2'"),
+                                        getMemberLocation(expr))
+                                        << classdecl << describeChangeKind(kind)
+                                        << fdecl->getQualifiedNameAsString()
+                                        << expr->getSourceRange();
+                                }
+                                return true;
+                            }
+                        }
+                    } else if (isa<CXXConstructExpr>(call)) {
+                    } else {
+                        assert(false);
+                    }
+                }
+            }
+        }
+        if (simplify) {
+            report(
+                DiagnosticsEngine::Warning,
+                "simplify construction of %0 with %1", expr->getExprLoc())
+                << classdecl << describeChangeKind(kind)
+                << expr->getSourceRange();
+        }
+        return true;
+    }
+
+    auto consDecl = expr->getConstructor();
+    for (unsigned i = 0; i != consDecl->getNumParams(); ++i) {
+        auto t = consDecl->getParamDecl(i)->getType();
+        if (loplugin::TypeCheck(t).NotSubstTemplateTypeParmType()
+            .LvalueReference().Const().NotSubstTemplateTypeParmType()
+            .Class("OUString").Namespace("rtl").GlobalNamespace())
+        {
+            auto argExpr = expr->getArg(i);
+            if (argExpr && i <= consDecl->getNumParams())
+            {
+                if (!hasOverloads(consDecl, expr->getNumArgs()))
+                {
+                    handleOUStringCtor(expr, argExpr, consDecl, true);
+                }
+            }
+        }
+        if (loplugin::TypeCheck(t).NotSubstTemplateTypeParmType()
+            .LvalueReference().Const().NotSubstTemplateTypeParmType()
+            .Class("OString").Namespace("rtl").GlobalNamespace())
+        {
+            auto argExpr = expr->getArg(i);
+            if (argExpr && i <= consDecl->getNumParams())
+            {
+                if (!hasOverloads(consDecl, expr->getNumArgs()))
+                {
+                    handleOStringCtor(expr, argExpr, consDecl, true);
+                }
+            }
+        }
+    }
+
+    return true;
+}
+
+bool StringConstant::VisitReturnStmt(ReturnStmt const * stmt) {
+    if (ignoreLocation(stmt)) {
+        return true;
+    }
+    auto const e1 = stmt->getRetValue();
+    if (e1 == nullptr) {
+        return true;
+    }
+    auto const tc1 = loplugin::TypeCheck(e1->getType().getTypePtr());
+    if (!(tc1.Class("OString").Namespace("rtl").GlobalNamespace()
+          || tc1.Class("OUString").Namespace("rtl").GlobalNamespace()))
+    {
+        return true;
+    }
+    assert(!returnTypes_.empty());
+    auto const tc2 = loplugin::TypeCheck(returnTypes_.top().getTypePtr());
+    if (!(tc2.Class("OString").Namespace("rtl").GlobalNamespace()
+          || tc2.Class("OUString").Namespace("rtl").GlobalNamespace()))
+    {
+        return true;
+    }
+    auto const e2 = dyn_cast<CXXFunctionalCastExpr>(e1->IgnoreImplicit());
+    if (e2 == nullptr) {
+        return true;
+    }
+    auto const e3 = dyn_cast<CXXBindTemporaryExpr>(e2->getSubExpr());
+    if (e3 == nullptr) {
+        return true;
+    }
+    auto const e4 = dyn_cast<CXXConstructExpr>(e3->getSubExpr());
+    if (e4 == nullptr) {
+        return true;
+    }
+    if (e4->getNumArgs() != 2) {
+        return true;
+    }
+    auto const t = e4->getArg(0)->getType();
+    if (!(t.isConstQualified() && t->isConstantArrayType())) {
+        return true;
+    }
+    auto const e5 = e4->getArg(1);
+    if (!(isa<CXXDefaultArgExpr>(e5)
+          && (loplugin::TypeCheck(e5->getType()).Struct("Dummy").Namespace("libreoffice_internal")
+              .Namespace("rtl").GlobalNamespace())))
+    {
+        return true;
+    }
+    report(DiagnosticsEngine::Warning, "elide constructor call", e1->getBeginLoc())
+        << e1->getSourceRange();
+    return true;
+}
+
+std::string StringConstant::describeChangeKind(ChangeKind kind) {
+    switch (kind) {
+    case ChangeKind::Char:
+        return "string constant argument";
+    case ChangeKind::CharLen:
+        return "string constant and matching length arguments";
+    case ChangeKind::SingleChar:
+        return "sal_Unicode argument";
+    case ChangeKind::OUStringChar:
+        return "OUStringChar argument";
+    }
+    llvm_unreachable("unknown change kind");
+}
+
+bool StringConstant::isStringConstant(
+    Expr const * expr, unsigned * size, bool * nonArray, ContentKind * content,
+    bool * embeddedNuls, bool * terminatingNul,
+    std::vector<char32_t> * utf8Content)
+{
+    assert(expr != nullptr);
+    assert(size != nullptr);
+    assert(nonArray != nullptr);
+    assert(content != nullptr);
+    assert(embeddedNuls != nullptr);
+    assert(terminatingNul != nullptr);
+    QualType t = expr->getType();
+    // Look inside RTL_CONSTASCII_STRINGPARAM:
+    if (loplugin::TypeCheck(t).Pointer().Const().Char()) {
+        auto e2 = dyn_cast<UnaryOperator>(expr);
+        if (e2 != nullptr && e2->getOpcode() == UO_AddrOf) {
+            auto e3 = dyn_cast<ArraySubscriptExpr>(
+                e2->getSubExpr()->IgnoreParenImpCasts());
+            if (e3 == nullptr || !isZero(e3->getIdx()->IgnoreParenImpCasts())) {
+                return false;
+            }
+            expr = e3->getBase()->IgnoreParenImpCasts();
+            t = expr->getType();
+        }
+    }
+    if (!t.isConstQualified()) {
+        return false;
+    }
+    DeclRefExpr const * dre = dyn_cast<DeclRefExpr>(expr);
+    if (dre != nullptr) {
+        VarDecl const * var = dyn_cast<VarDecl>(dre->getDecl());
+        if (var != nullptr) {
+            Expr const * init = var->getAnyInitializer();
+            if (init != nullptr) {
+                expr = init->IgnoreParenImpCasts();
+            }
+        }
+    }
+    bool isPtr;
+    if (loplugin::TypeCheck(t).Pointer().Const().Char()) {
+        isPtr = true;
+    } else if (t->isConstantArrayType()
+               && (loplugin::TypeCheck(
+                       t->getAsArrayTypeUnsafe()->getElementType())
+                   .Char()))
+    {
+        isPtr = false;
+    } else {
+        return false;
+    }
+    clang::StringLiteral const * lit = dyn_cast<clang::StringLiteral>(expr);
+    if (lit != nullptr) {
+        if (!(compat::isOrdinary(lit) || lit->isUTF8())) {
+            return false;
+        }
+        unsigned n = lit->getLength();
+        ContentKind cont = ContentKind::Ascii;
+        bool emb = false;
+        char32_t val = 0;
+        enum class Utf8State { Start, E0, EB, F0, F4, Trail1, Trail2, Trail3 };
+        Utf8State s = Utf8State::Start;
+        StringRef str = lit->getString();
+        for (unsigned i = 0; i != n; ++i) {
+            auto const c = static_cast<unsigned char>(str[i]);
+            if (c == '\0') {
+                emb = true;
+            }
+            switch (s) {
+            case Utf8State::Start:
+                if (c >= 0x80) {
+                    if (c >= 0xC2 && c <= 0xDF) {
+                        val = c & 0x1F;
+                        s = Utf8State::Trail1;
+                    } else if (c == 0xE0) {
+                        val = c & 0x0F;
+                        s = Utf8State::E0;
+                    } else if ((c >= 0xE1 && c <= 0xEA)
+                               || (c >= 0xEE && c <= 0xEF))
+                    {
+                        val = c & 0x0F;
+                        s = Utf8State::Trail2;
+                    } else if (c == 0xEB) {
+                        val = c & 0x0F;
+                        s = Utf8State::EB;
+                    } else if (c == 0xF0) {
+                        val = c & 0x03;
+                        s = Utf8State::F0;
+                    } else if (c >= 0xF1 && c <= 0xF3) {
+                        val = c & 0x03;
+                        s = Utf8State::Trail3;
+                    } else if (c == 0xF4) {
+                        val = c & 0x03;
+                        s = Utf8State::F4;
+                    } else {
+                        cont = ContentKind::Arbitrary;
+                    }
+                } else if (utf8Content != nullptr
+                           && cont != ContentKind::Arbitrary)
+                {
+                    utf8Content->push_back(c);
+                }
+                break;
+            case Utf8State::E0:
+                if (c >= 0xA0 && c <= 0xBF) {
+                    val = (val << 6) | (c & 0x3F);
+                    s = Utf8State::Trail1;
+                } else {
+                    cont = ContentKind::Arbitrary;
+                    s = Utf8State::Start;
+                }
+                break;
+            case Utf8State::EB:
+                if (c >= 0x80 && c <= 0x9F) {
+                    val = (val << 6) | (c & 0x3F);
+                    s = Utf8State::Trail1;
+                } else {
+                    cont = ContentKind::Arbitrary;
+                    s = Utf8State::Start;
+                }
+                break;
+            case Utf8State::F0:
+                if (c >= 0x90 && c <= 0xBF) {
+                    val = (val << 6) | (c & 0x3F);
+                    s = Utf8State::Trail2;
+                } else {
+                    cont = ContentKind::Arbitrary;
+                    s = Utf8State::Start;
+                }
+                break;
+            case Utf8State::F4:
+                if (c >= 0x80 && c <= 0x8F) {
+                    val = (val << 6) | (c & 0x3F);
+                    s = Utf8State::Trail2;
+                } else {
+                    cont = ContentKind::Arbitrary;
+                    s = Utf8State::Start;
+                }
+                break;
+            case Utf8State::Trail1:
+                if (c >= 0x80 && c <= 0xBF) {
+                    cont = ContentKind::Utf8;
+                    if (utf8Content != nullptr)
+                    {
+                        utf8Content->push_back((val << 6) | (c & 0x3F));
+                        val = 0;
+                    }
+                } else {
+                    cont = ContentKind::Arbitrary;
+                }
+                s = Utf8State::Start;
+                break;
+            case Utf8State::Trail2:
+                if (c >= 0x80 && c <= 0xBF) {
+                    val = (val << 6) | (c & 0x3F);
+                    s = Utf8State::Trail1;
+                } else {
+                    cont = ContentKind::Arbitrary;
+                    s = Utf8State::Start;
+                }
+                break;
+            case Utf8State::Trail3:
+                if (c >= 0x80 && c <= 0xBF) {
+                    val = (val << 6) | (c & 0x3F);
+                    s = Utf8State::Trail2;
+                } else {
+                    cont = ContentKind::Arbitrary;
+                    s = Utf8State::Start;
+                }
+                break;
+            }
+        }
+        *size = n;
+        *nonArray = isPtr;
+        *content = cont;
+        *embeddedNuls = emb;
+        *terminatingNul = true;
+        return true;
+    }
+    APValue v;
+    if (!expr->isCXX11ConstantExpr(compiler.getASTContext(), &v)) {
+        return false;
+    }
+    switch (v.getKind()) {
+    case APValue::LValue:
+        {
+            Expr const * e = v.getLValueBase().dyn_cast<Expr const *>();
+            if (e == nullptr) {
+                return false;
+            }
+            if (!v.getLValueOffset().isZero()) {
+                return false; //TODO
+            }
+            Expr const * e2 = e->IgnoreParenImpCasts();
+            if (e2 != e) {
+                return isStringConstant(
+                    e2, size, nonArray, content, embeddedNuls, terminatingNul);
+            }
+            //TODO: string literals are represented as recursive LValues???
+            llvm::APInt n
+                = compiler.getASTContext().getAsConstantArrayType(t)->getSize();
+            assert(n != 0);
+            --n;
+            assert(n.ule(std::numeric_limits<unsigned>::max()));
+            *size = static_cast<unsigned>(n.getLimitedValue());
+            *nonArray = isPtr || *nonArray;
+            *content = ContentKind::Ascii; //TODO
+            *embeddedNuls = false; //TODO
+            *terminatingNul = true;
+            return true;
+        }
+    case APValue::Array:
+        {
+            if (v.hasArrayFiller()) { //TODO: handle final NULL filler?
+                return false;
+            }
+            unsigned n = v.getArraySize();
+            assert(n != 0);
+            ContentKind cont = ContentKind::Ascii;
+            bool emb = false;
+            //TODO: check for ContentType::Utf8
+            for (unsigned i = 0; i != n - 1; ++i) {
+                APValue e(v.getArrayInitializedElt(i));
+                if (!e.isInt()) { //TODO: assert?
+                    return false;
+                }
+                APSInt iv = e.getInt();
+                if (iv == 0) {
+                    emb = true;
+                } else if (iv.uge(0x80)) {
+                    cont = ContentKind::Arbitrary;
+                }
+            }
+            APValue e(v.getArrayInitializedElt(n - 1));
+            if (!e.isInt()) { //TODO: assert?
+                return false;
+            }
+            bool trm = e.getInt() == 0;
+            *size = trm ? n - 1 : n;
+            *nonArray = isPtr;
+            *content = cont;
+            *embeddedNuls = emb;
+            *terminatingNul = trm;
+            return true;
+        }
+    default:
+        assert(false); //TODO???
+        return false;
+    }
+}
+
+bool StringConstant::isZero(Expr const * expr) {
+    APSInt res;
+    return compat::EvaluateAsInt(expr, res, compiler.getASTContext()) && res == 0;
+}
+
+void StringConstant::reportChange(
+    Expr const * expr, ChangeKind kind, std::string const & original,
+    std::string const & replacement, PassThrough pass, bool nonArray,
+    char const * rewriteFrom, char const * rewriteTo)
+{
+    assert((rewriteFrom == nullptr) == (rewriteTo == nullptr));
+    if (pass != PassThrough::No && !calls_.empty()) {
+        Expr const * call = calls_.top();
+        CallExpr::const_arg_iterator argsBeg;
+        CallExpr::const_arg_iterator argsEnd;
+        if (isa<CallExpr>(call)) {
+            argsBeg = cast<CallExpr>(call)->arg_begin();
+            argsEnd = cast<CallExpr>(call)->arg_end();
+        } else if (isa<CXXConstructExpr>(call)) {
+            argsBeg = cast<CXXConstructExpr>(call)->arg_begin();
+            argsEnd = cast<CXXConstructExpr>(call)->arg_end();
+        } else {
+            assert(false);
+        }
+        for (auto i(argsBeg); i != argsEnd; ++i) {
+            Expr const * e = (*i)->IgnoreParenImpCasts();
+            if (isa<CXXBindTemporaryExpr>(e)) {
+                e = cast<CXXBindTemporaryExpr>(e)->getSubExpr()
+                    ->IgnoreParenImpCasts();
+            }
+            if (e == expr) {
+                if (isa<CallExpr>(call)) {
+                    FunctionDecl const * fdecl
+                        = cast<CallExpr>(call)->getDirectCallee();
+                    if (fdecl == nullptr) {
+                        break;
+                    }
+                    loplugin::DeclCheck dc(fdecl);
+                    if (pass == PassThrough::EmptyConstantString) {
+                        if ((dc.Function("equals").Class("OUString")
+                             .Namespace("rtl").GlobalNamespace())
+                            || (dc.Operator(OO_EqualEqual).Namespace("rtl")
+                                .GlobalNamespace()))
+                        {
+                            report(
+                                DiagnosticsEngine::Warning,
+                                ("rewrite call of '%0' with call of %1 with"
+                                 " empty string constant argument as call of"
+                                 " 'rtl::OUString::isEmpty'"),
+                                getMemberLocation(call))
+                                << fdecl->getQualifiedNameAsString() << original
+                                << call->getSourceRange();
+                            return;
+                        }
+                        if (dc.Operator(OO_ExclaimEqual).Namespace("rtl")
+                            .GlobalNamespace())
+                        {
+                            report(
+                                DiagnosticsEngine::Warning,
+                                ("rewrite call of '%0' with call of %1 with"
+                                 " empty string constant argument as call of"
+                                 " '!rtl::OUString::isEmpty'"),
+                                getMemberLocation(call))
+                                << fdecl->getQualifiedNameAsString() << original
+                                << call->getSourceRange();
+                            return;
+                        }
+                        if ((dc.Operator(OO_Plus).Namespace("rtl")
+                             .GlobalNamespace())
+                            || (dc.Operator(OO_Plus).Class("OUString")
+                                .Namespace("rtl").GlobalNamespace()))
+                        {
+                            report(
+                                DiagnosticsEngine::Warning,
+                                ("call of '%0' with suspicious call of %1 with"
+                                 " empty string constant argument"),
+                                getMemberLocation(call))
+                                << fdecl->getQualifiedNameAsString() << original
+                                << call->getSourceRange();
+                            return;
+                        }
+                        if (dc.Operator(OO_Equal).Class("OUString")
+                            .Namespace("rtl").GlobalNamespace())
+                        {
+                            report(
+                                DiagnosticsEngine::Warning,
+                                ("rewrite call of '%0' with call of %1 with"
+                                 " empty string constant argument as call of"
+                                 " rtl::OUString::call"),
+                                getMemberLocation(call))
+                                << fdecl->getQualifiedNameAsString() << original
+                                << call->getSourceRange();
+                            return;
+                        }
+                        report(
+                            DiagnosticsEngine::Warning,
+                            "TODO call inside %0", getMemberLocation(expr))
+                            << fdecl->getQualifiedNameAsString()
+                            << expr->getSourceRange();
+                        return;
+                    } else {
+                        assert(pass == PassThrough::NonEmptyConstantString);
+                        if ((dc.Function("equals").Class("OUString")
+                             .Namespace("rtl").GlobalNamespace())
+                            || (dc.Operator(OO_Equal).Class("OUString")
+                                .Namespace("rtl").GlobalNamespace())
+                            || (dc.Operator(OO_EqualEqual).Namespace("rtl")
+                                .GlobalNamespace())
+                            || (dc.Operator(OO_ExclaimEqual).Namespace("rtl")
+                                .GlobalNamespace()))
+                        {
+                            report(
+                                DiagnosticsEngine::Warning,
+                                "elide call of %0 with %1 in call of '%2'",
+                                getMemberLocation(expr))
+                                << original << describeChangeKind(kind)
+                                << fdecl->getQualifiedNameAsString()
+                                << expr->getSourceRange();
+                            return;
+                        }
+                        report(
+                            DiagnosticsEngine::Warning,
+                            ("rewrite call of %0 with %1 in call of '%2' as"
+                             " (implicit) construction of 'OUString'"),
+                            getMemberLocation(expr))
+                            << original << describeChangeKind(kind)
+                            << fdecl->getQualifiedNameAsString()
+                            << expr->getSourceRange();
+                        return;
+                    }
+                } else if (isa<CXXConstructExpr>(call)) {
+                    auto classdecl = cast<CXXConstructExpr>(call)
+                        ->getConstructor()->getParent();
+                    loplugin::DeclCheck dc(classdecl);
+                    if (dc.Class("OUString").Namespace("rtl").GlobalNamespace()
+                        || (dc.Class("OUStringBuffer").Namespace("rtl")
+                            .GlobalNamespace()))
+                    {
+                        //TODO: propagate further out?
+                        if (pass == PassThrough::EmptyConstantString) {
+                            report(
+                                DiagnosticsEngine::Warning,
+                                ("rewrite construction of %0 with call of %1"
+                                 " with empty string constant argument as"
+                                 " default construction of %0"),
+                                getMemberLocation(call))
+                                << classdecl << original
+                                << call->getSourceRange();
+                        } else {
+                            assert(pass == PassThrough::NonEmptyConstantString);
+                            report(
+                                DiagnosticsEngine::Warning,
+                                ("elide call of %0 with %1 in construction of"
+                                 " %2"),
+                                getMemberLocation(expr))
+                                << original << describeChangeKind(kind)
+                                << classdecl << expr->getSourceRange();
+                        }
+                        return;
+                    }
+                } else {
+                    assert(false);
+                }
+            }
+        }
+    }
+    if (rewriter != nullptr && !nonArray && rewriteFrom != nullptr) {
+        SourceLocation loc = getMemberLocation(expr);
+        while (compiler.getSourceManager().isMacroArgExpansion(loc)) {
+            loc = compiler.getSourceManager().getImmediateMacroCallerLoc(loc);
+        }
+        if (compiler.getSourceManager().isMacroBodyExpansion(loc)) {
+            loc = compiler.getSourceManager().getSpellingLoc(loc);
+        }
+        unsigned n = Lexer::MeasureTokenLength(
+            loc, compiler.getSourceManager(), compiler.getLangOpts());
+        if ((std::string(compiler.getSourceManager().getCharacterData(loc), n)
+             == rewriteFrom)
+            && replaceText(loc, n, rewriteTo))
+        {
+            return;
+        }
+    }
+    report(
+        DiagnosticsEngine::Warning,
+        "rewrite call of '%0' with %1 as call of '%2'%3",
+        getMemberLocation(expr))
+        << original << describeChangeKind(kind) << replacement
+        << adviseNonArray(nonArray) << expr->getSourceRange();
+}
+
+void StringConstant::checkEmpty(
+    CallExpr const * expr, FunctionDecl const * callee, TreatEmpty treatEmpty,
+    unsigned size, std::string * replacement)
+{
+    assert(replacement != nullptr);
+    if (size == 0) {
+        switch (treatEmpty) {
+        case TreatEmpty::DefaultCtor:
+            *replacement = "rtl::OUString default constructor";
+            break;
+        case TreatEmpty::CheckEmpty:
+            *replacement = "rtl::OUString::isEmpty";
+            break;
+        case TreatEmpty::Error:
+            report(
+                DiagnosticsEngine::Warning,
+                "call of '%0' with suspicious empty string constant argument",
+                getMemberLocation(expr))
+                << callee->getQualifiedNameAsString() << expr->getSourceRange();
+            break;
+        }
+    }
+}
+
+void StringConstant::handleChar(
+    CallExpr const * expr, unsigned arg, FunctionDecl const * callee,
+    std::string const & replacement, TreatEmpty treatEmpty, bool literal,
+    char const * rewriteFrom, char const * rewriteTo)
+{
+    unsigned n;
+    bool nonArray;
+    ContentKind cont;
+    bool emb;
+    bool trm;
+    if (!isStringConstant(
+            expr->getArg(arg)->IgnoreParenImpCasts(), &n, &nonArray, &cont,
+            &emb, &trm))
+    {
+        return;
+    }
+    if (cont != ContentKind::Ascii) {
+        report(
+            DiagnosticsEngine::Warning,
+            ("call of '%0' with string constant argument containing non-ASCII"
+             " characters"),
+            getMemberLocation(expr))
+            << callee->getQualifiedNameAsString() << expr->getSourceRange();
+        return;
+    }
+    if (emb) {
+        report(
+            DiagnosticsEngine::Warning,
+            ("call of '%0' with string constant argument containing embedded"
+             " NULLs"),
+            getMemberLocation(expr))
+            << callee->getQualifiedNameAsString() << expr->getSourceRange();
+        return;
+    }
+    if (!trm) {
+        report(
+            DiagnosticsEngine::Warning,
+            ("call of '%0' with string constant argument lacking a terminating"
+             " NULL"),
+            getMemberLocation(expr))
+            << callee->getQualifiedNameAsString() << expr->getSourceRange();
+        return;
+    }
+    std::string repl(replacement);
+    checkEmpty(expr, callee, treatEmpty, n, &repl);
+    if (!repl.empty()) {
+        reportChange(
+            expr, ChangeKind::Char, callee->getQualifiedNameAsString(), repl,
+            (literal
+             ? (n == 0
+                ? PassThrough::EmptyConstantString
+                : PassThrough::NonEmptyConstantString)
+             : PassThrough::No),
+            nonArray, rewriteFrom, rewriteTo);
+    }
+}
+
+void StringConstant::handleCharLen(
+    CallExpr const * expr, unsigned arg1, unsigned arg2,
+    FunctionDecl const * callee, std::string const & replacement,
+    TreatEmpty treatEmpty)
+{
+    // Especially for f(RTL_CONSTASCII_STRINGPARAM("foo")), where
+    // RTL_CONSTASCII_STRINGPARAM expands to complicated expressions involving
+    // (&(X)[0] sub-expressions (and it might or might not be better to handle
+    // that at the level of non-expanded macros instead, but I have not found
+    // out how to do that yet anyway):
+    unsigned n;
+    bool nonArray;
+    ContentKind cont;
+    bool emb;
+    bool trm;
+    if (!(isStringConstant(
+              expr->getArg(arg1)->IgnoreParenImpCasts(), &n, &nonArray, &cont,
+              &emb, &trm)
+          && trm))
+    {
+        return;
+    }
+    APSInt res;
+    if (compat::EvaluateAsInt(expr->getArg(arg2), res, compiler.getASTContext())) {
+        if (res != n) {
+            return;
+        }
+    } else {
+        UnaryOperator const * op = dyn_cast<UnaryOperator>(
+            expr->getArg(arg1)->IgnoreParenImpCasts());
+        if (op == nullptr || op->getOpcode() != UO_AddrOf) {
+            return;
+        }
+        ArraySubscriptExpr const * subs = dyn_cast<ArraySubscriptExpr>(
+            op->getSubExpr()->IgnoreParenImpCasts());
+        if (subs == nullptr) {
+            return;
+        }
+        unsigned n2;
+        bool nonArray2;
+        ContentKind cont2;
+        bool emb2;
+        bool trm2;
+        if (!(isStringConstant(
+                  subs->getBase()->IgnoreParenImpCasts(), &n2, &nonArray2,
+                  &cont2, &emb2, &trm2)
+              && n2 == n && cont2 == cont && emb2 == emb && trm2 == trm
+                  //TODO: same strings
+              && compat::EvaluateAsInt(subs->getIdx(), res, compiler.getASTContext())
+              && res == 0))
+        {
+            return;
+        }
+    }
+    if (cont != ContentKind::Ascii) {
+        report(
+            DiagnosticsEngine::Warning,
+            ("call of '%0' with string constant argument containing non-ASCII"
+             " characters"),
+            getMemberLocation(expr))
+            << callee->getQualifiedNameAsString() << expr->getSourceRange();
+    }
+    if (emb) {
+        return;
+    }
+    std::string repl(replacement);
+    checkEmpty(expr, callee, treatEmpty, n, &repl);
+    reportChange(
+        expr, ChangeKind::CharLen, callee->getQualifiedNameAsString(), repl,
+        PassThrough::No, nonArray, nullptr, nullptr);
+}
+
+void StringConstant::handleOUStringCtor(
+    CallExpr const * expr, unsigned arg, FunctionDecl const * callee,
+    bool explicitFunctionalCastNotation)
+{
+    handleOUStringCtor(expr, expr->getArg(arg), callee, explicitFunctionalCastNotation);
+}
+
+void StringConstant::handleOStringCtor(
+    CallExpr const * expr, unsigned arg, FunctionDecl const * callee,
+    bool explicitFunctionalCastNotation)
+{
+    handleOStringCtor(expr, expr->getArg(arg), callee, explicitFunctionalCastNotation);
+}
+
+void StringConstant::handleOUStringCtor(
+    Expr const * expr, Expr const * argExpr, FunctionDecl const * callee,
+    bool explicitFunctionalCastNotation)
+{
+    handleStringCtor(expr, argExpr, callee, explicitFunctionalCastNotation, StringKind::Unicode);
+}
+
+void StringConstant::handleOStringCtor(
+    Expr const * expr, Expr const * argExpr, FunctionDecl const * callee,
+    bool explicitFunctionalCastNotation)
+{
+    handleStringCtor(expr, argExpr, callee, explicitFunctionalCastNotation, StringKind::Char);
+}
+
+void StringConstant::handleStringCtor(
+    Expr const * expr, Expr const * argExpr, FunctionDecl const * callee,
+    bool explicitFunctionalCastNotation, StringKind stringKind)
+{
+    auto e0 = argExpr->IgnoreParenImpCasts();
+    if (auto const e1 = dyn_cast<CXXMemberCallExpr>(e0)) {
+        if (auto const e2 = dyn_cast<CXXConversionDecl>(e1->getMethodDecl())) {
+            if (loplugin::TypeCheck(e2->getConversionType()).ClassOrStruct("basic_string_view")
+                .StdNamespace())
+            {
+                e0 = e1->getImplicitObjectArgument()->IgnoreParenImpCasts();
+            }
+        }
+    }
+    auto e1 = dyn_cast<CXXFunctionalCastExpr>(e0);
+    if (e1 == nullptr) {
+        if (explicitFunctionalCastNotation) {
+            return;
+        }
+    } else {
+        e0 = e1->getSubExpr()->IgnoreParenImpCasts();
+    }
+    auto e2 = dyn_cast<CXXBindTemporaryExpr>(e0);
+    if (e2 == nullptr) {
+        return;
+    }
+    auto e3 = dyn_cast<CXXConstructExpr>(
+        e2->getSubExpr()->IgnoreParenImpCasts());
+    if (e3 == nullptr) {
+        return;
+    }
+    if (!loplugin::DeclCheck(e3->getConstructor()).MemberFunction()
+        .Class(stringKind == StringKind::Unicode ? "OUString" : "OString").Namespace("rtl").GlobalNamespace())
+    {
+        return;
+    }
+    if (e3->getNumArgs() == 0) {
+        report(
+            DiagnosticsEngine::Warning,
+            ("in call of '%0', replace default-constructed 'OUString' with an"
+             " empty string literal"),
+            e3->getExprLoc())
+            << callee->getQualifiedNameAsString() << expr->getSourceRange();
+        return;
+    }
+    if (e3->getNumArgs() == 1
+        && e3->getConstructor()->getNumParams() == 1
+        && (loplugin::TypeCheck(
+                e3->getConstructor()->getParamDecl(0)->getType())
+            .Typedef(stringKind == StringKind::Unicode ? "sal_Unicode" : "char").GlobalNamespace()))
+    {
+        // It may not be easy to rewrite OUString(c), esp. given there is no
+        // OUString ctor taking an OUStringChar arg, so don't warn there:
+        if (!explicitFunctionalCastNotation) {
+            report(
+                DiagnosticsEngine::Warning,
+                ("in call of '%0', replace 'OUString' constructed from a"
+                 " 'sal_Unicode' with an 'OUStringChar'"),
+                e3->getExprLoc())
+                << callee->getQualifiedNameAsString() << expr->getSourceRange();
+        }
+        return;
+    }
+    if (e3->getNumArgs() != 2) {
+        return;
+    }
+    unsigned n;
+    bool nonArray;
+    ContentKind cont;
+    bool emb;
+    bool trm;
+    if (!isStringConstant(
+            e3->getArg(0)->IgnoreParenImpCasts(), &n, &nonArray, &cont, &emb,
+            &trm))
+    {
+        return;
+    }
+    //TODO: cont, emb, trm
+    if (rewriter != nullptr) {
+        auto loc1 = e3->getBeginLoc();
+        auto range = e3->getParenOrBraceRange();
+        if (loc1.isFileID() && range.getBegin().isFileID()
+            && range.getEnd().isFileID())
+        {
+            auto loc2 = range.getBegin();
+            for (bool first = true;; first = false) {
+                unsigned n = Lexer::MeasureTokenLength(
+                    loc2, compiler.getSourceManager(), compiler.getLangOpts());
+                if (!first) {
+                    StringRef s(
+                        compiler.getSourceManager().getCharacterData(loc2), n);
+                    while (s.startswith("\\\n")) {
+                        s = s.drop_front(2);
+                        while (!s.empty()
+                               && (s.front() == ' ' || s.front() == '\t'
+                                   || s.front() == '\n' || s.front() == '\v'
+                                   || s.front() == '\f'))
+                        {
+                            s = s.drop_front(1);
+                        }
+                    }
+                    if (!(s.empty() || s.startswith("/*") || s.startswith("//")
+                          || s == "\\"))
+                    {
+                        break;
+                    }
+                }
+                loc2 = loc2.getLocWithOffset(std::max<unsigned>(n, 1));
+            }
+            auto loc3 = range.getEnd();
+            for (;;) {
+                auto l = Lexer::GetBeginningOfToken(
+                    loc3.getLocWithOffset(-1), compiler.getSourceManager(),
+                    compiler.getLangOpts());
+                unsigned n = Lexer::MeasureTokenLength(
+                    l, compiler.getSourceManager(), compiler.getLangOpts());
+                StringRef s(compiler.getSourceManager().getCharacterData(l), n);
+                while (s.startswith("\\\n")) {
+                    s = s.drop_front(2);
+                    while (!s.empty()
+                           && (s.front() == ' ' || s.front() == '\t'
+                               || s.front() == '\n' || s.front() == '\v'
+                               || s.front() == '\f'))
+                    {
+                        s = s.drop_front(1);
+                    }
+                }
+                if (!(s.empty() || s.startswith("/*") || s.startswith("//")
+                      || s == "\\"))
+                {
+                    break;
+                }
+                loc3 = l;
+            }
+            if (removeText(CharSourceRange(SourceRange(loc1, loc2), false))) {
+                if (removeText(SourceRange(loc3, range.getEnd()))) {
+                    return;
+                }
+                report(DiagnosticsEngine::Fatal, "Corrupt rewrite", loc3)
+                    << expr->getSourceRange();
+                return;
+            }
+        }
+    }
+    report(
+        DiagnosticsEngine::Warning,
+        ("in call of '%0', replace 'OUString' constructed from a string literal"
+         " directly with the string literal"),
+        e3->getExprLoc())
+        << callee->getQualifiedNameAsString() << expr->getSourceRange();
+}
+
+void StringConstant::handleFunArgOstring(
+    CallExpr const * expr, unsigned arg, FunctionDecl const * callee)
+{
+    auto argExpr = expr->getArg(arg)->IgnoreParenImpCasts();
+    unsigned n;
+    bool nonArray;
+    ContentKind cont;
+    bool emb;
+    bool trm;
+    if (isStringConstant(argExpr, &n, &nonArray, &cont, &emb, &trm)) {
+        if (cont != ContentKind::Ascii || emb) {
+            return;
+        }
+        if (!trm) {
+            report(
+                DiagnosticsEngine::Warning,
+                ("call of '%0' with string constant argument lacking a"
+                 " terminating NULL"),
+                getMemberLocation(expr))
+                << callee->getQualifiedNameAsString() << expr->getSourceRange();
+            return;
+        }
+        std::string repl;
+        checkEmpty(expr, callee, TreatEmpty::Error, n, &repl);
+        if (nonArray) {
+            report(
+                DiagnosticsEngine::Warning,
+                ("in call of '%0' with non-array string constant argument,"
+                 " turn the non-array string constant into an array"),
+                getMemberLocation(expr))
+                << callee->getQualifiedNameAsString() << expr->getSourceRange();
+        }
+    } else if (auto cexpr = lookForCXXConstructExpr(argExpr)) {
+        auto classdecl = cexpr->getConstructor()->getParent();
+        if (loplugin::DeclCheck(classdecl).Class("OString").Namespace("rtl")
+            .GlobalNamespace())
+        {
+            switch (cexpr->getConstructor()->getNumParams()) {
+            case 0:
+                report(
+                    DiagnosticsEngine::Warning,
+                    ("in call of '%0', replace empty %1 constructor with empty"
+                     " string literal"),
+                    cexpr->getLocation())
+                    << callee->getQualifiedNameAsString() << classdecl
+                    << expr->getSourceRange();
+                break;
+            case 2:
+                if (isStringConstant(
+                        cexpr->getArg(0)->IgnoreParenImpCasts(), &n, &nonArray,
+                        &cont, &emb, &trm))
+                {
+                    APSInt res;
+                    if (compat::EvaluateAsInt(cexpr->getArg(1),
+                            res, compiler.getASTContext()))
+                    {
+                        if (res == n && !emb && trm) {
+                            report(
+                                DiagnosticsEngine::Warning,
+                                ("in call of '%0', elide explicit %1"
+                                 " constructor%2"),
+                                cexpr->getLocation())
+                                << callee->getQualifiedNameAsString()
+                                << classdecl << adviseNonArray(nonArray)
+                                << expr->getSourceRange();
+                        }
+                    } else {
+                        if (emb) {
+                            report(
+                                DiagnosticsEngine::Warning,
+                                ("call of %0 constructor with string constant"
+                                 " argument containing embedded NULLs"),
+                                cexpr->getLocation())
+                                << classdecl << cexpr->getSourceRange();
+                            return;
+                        }
+                        if (!trm) {
+                            report(
+                                DiagnosticsEngine::Warning,
+                                ("call of %0 constructor with string constant"
+                                 " argument lacking a terminating NULL"),
+                                cexpr->getLocation())
+                                << classdecl << cexpr->getSourceRange();
+                            return;
+                        }
+                        report(
+                            DiagnosticsEngine::Warning,
+                            "in call of '%0', elide explicit %1 constructor%2",
+                            cexpr->getLocation())
+                            << callee->getQualifiedNameAsString() << classdecl
+                            << adviseNonArray(nonArray)
+                            << expr->getSourceRange();
+                    }
+                }
+                break;
+            default:
+                break;
+            }
+        }
+    }
+}
+
+loplugin::Plugin::Registration< StringConstant > X("stringconstant", true);
+
+}
+
+/* vim:set shiftwidth=4 softtabstop=4 expandtab: */