compiler check for rtl::OUStringConcat instances

Something like auto str = "string" + OUString::number( 10 ); will
not be OUString but actually rtl::OUStringConcat (which gets implicitly
converted to OUString, but not with auto). Since those refer to temporaries
from the expression, they should not outlive the expression.

Change-Id: Ib4cde4b38befb3d49927d0cf01c52ebb2d36df89
Reviewed-on: https://gerrit.libreoffice.org/78830
Tested-by: Jenkins
Reviewed-by: Luboš Luňák <l.lunak@collabora.com>

compilerplugins/clang/stringconcatliterals.cxx

@@ -0,0 +1,162 @@
+/* -*- 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/.
+ */
+
+#ifndef LO_CLANG_SHARED_PLUGINS
+
+#include "plugin.hxx"
+#include "check.hxx"
+
+namespace {
+
+Expr const * stripCtor(Expr const * expr) {
+    auto e1 = expr;
+    if (auto const e = dyn_cast<CXXFunctionalCastExpr>(e1)) {
+        e1 = e->getSubExpr()->IgnoreParenImpCasts();
+    }
+    if (auto const e = dyn_cast<CXXBindTemporaryExpr>(e1)) {
+        e1 = e->getSubExpr()->IgnoreParenImpCasts();
+    }
+    auto const e2 = dyn_cast<CXXConstructExpr>(e1);
+    if (e2 == nullptr) {
+        return expr;
+    }
+    auto qt = loplugin::DeclCheck(e2->getConstructor());
+    if (qt.MemberFunction().Struct("OStringLiteral").Namespace("rtl").GlobalNamespace()) {
+        if (e2->getNumArgs() == 1) {
+            return e2->getArg(0)->IgnoreParenImpCasts();
+        }
+        return expr;
+    }
+    if (!((qt.MemberFunction().Class("OString").Namespace("rtl")
+           .GlobalNamespace())
+          || (qt.MemberFunction().Class("OUString").Namespace("rtl")
+              .GlobalNamespace())
+          || qt.MemberFunction().Struct("OUStringLiteral").Namespace("rtl").GlobalNamespace()))
+    {
+        return expr;
+    }
+    if (e2->getNumArgs() != 2) {
+        return expr;
+    }
+    return e2->getArg(0)->IgnoreParenImpCasts();
+}
+
+class StringConcatLiterals:
+    public loplugin::FilteringPlugin<StringConcatLiterals>
+{
+public:
+    explicit StringConcatLiterals(loplugin::InstantiationData const & data):
+        FilteringPlugin(data) {}
+
+    void run() override
+    { TraverseDecl(compiler.getASTContext().getTranslationUnitDecl()); }
+
+    bool VisitCallExpr(CallExpr const * expr);
+
+private:
+    bool isStringLiteral(Expr const * expr);
+};
+
+bool StringConcatLiterals::VisitCallExpr(CallExpr const * expr) {
+    if (ignoreLocation(expr)) {
+        return true;
+    }
+    FunctionDecl const * fdecl = expr->getDirectCallee();
+    if (fdecl == nullptr) {
+        return true;
+    }
+    OverloadedOperatorKind oo = fdecl->getOverloadedOperator();
+    if ((oo != OverloadedOperatorKind::OO_Plus
+         && oo != OverloadedOperatorKind::OO_LessLess)
+        || fdecl->getNumParams() != 2 || expr->getNumArgs() != 2
+        || !isStringLiteral(expr->getArg(1)->IgnoreParenImpCasts()))
+    {
+        return true;
+    }
+    SourceLocation leftLoc;
+    auto const leftExpr = expr->getArg(0)->IgnoreParenImpCasts();
+    if (isStringLiteral(leftExpr)) {
+        leftLoc = compat::getBeginLoc(leftExpr);
+    } else {
+        CallExpr const * left = dyn_cast<CallExpr>(leftExpr);
+        if (left == nullptr) {
+            return true;
+        }
+        FunctionDecl const * ldecl = left->getDirectCallee();
+        if (ldecl == nullptr) {
+            return true;
+        }
+        OverloadedOperatorKind loo = ldecl->getOverloadedOperator();
+        if ((loo != OverloadedOperatorKind::OO_Plus
+             && loo != OverloadedOperatorKind::OO_LessLess)
+            || ldecl->getNumParams() != 2 || left->getNumArgs() != 2
+            || !isStringLiteral(left->getArg(1)->IgnoreParenImpCasts()))
+        {
+            return true;
+        }
+        leftLoc = compat::getBeginLoc(left->getArg(1));
+    }
+
+    // We add an extra " " in the TOOLS_WARN_EXCEPTION macro, which triggers this plugin
+    if (loplugin::isSamePathname(
+            compiler.getSourceManager().getFilename(
+                compiler.getSourceManager().getSpellingLoc(
+                    compiler.getSourceManager().getImmediateMacroCallerLoc(
+                        compiler.getSourceManager().getImmediateMacroCallerLoc(
+                            compat::getBeginLoc(expr))))),
+            SRCDIR "/include/tools/diagnose_ex.h"))
+        return true;
+
+    StringRef name {
+        getFileNameOfSpellingLoc(
+            compiler.getSourceManager().getSpellingLoc(compat::getBeginLoc(expr))) };
+    if (loplugin::isSamePathname(
+            name, SRCDIR "/sal/qa/rtl/oustringbuffer/test_oustringbuffer_assign.cxx")
+        || loplugin::isSamePathname(
+            name, SRCDIR "/sal/qa/rtl/strings/test_ostring_concat.cxx")
+        || loplugin::isSamePathname(
+            name, SRCDIR "/sal/qa/rtl/strings/test_oustring_concat.cxx"))
+    {
+        return true;
+    }
+    CXXOperatorCallExpr const * op = dyn_cast<CXXOperatorCallExpr>(expr);
+    report(
+        DiagnosticsEngine::Warning,
+        "replace '%0' between string literals with juxtaposition",
+        op == nullptr ? expr->getExprLoc() : op->getOperatorLoc())
+        << (oo == OverloadedOperatorKind::OO_Plus ? "+" : "<<")
+        << SourceRange(leftLoc, compat::getEndLoc(expr->getArg(1)));
+    return true;
+}
+
+bool StringConcatLiterals::isStringLiteral(Expr const * expr) {
+    expr = stripCtor(expr);
+    if (!isa<clang::StringLiteral>(expr)) {
+        return false;
+    }
+    // OSL_THIS_FUNC may be defined as "" in include/osl/diagnose.h, so don't
+    // warn about expressions like 'SAL_INFO(..., OSL_THIS_FUNC << ":")' or
+    // 'OUString(OSL_THIS_FUNC) + ":"':
+    auto loc = compat::getBeginLoc(expr);
+    while (compiler.getSourceManager().isMacroArgExpansion(loc)) {
+        loc = compiler.getSourceManager().getImmediateMacroCallerLoc(loc);
+    }
+    return !compiler.getSourceManager().isMacroBodyExpansion(loc)
+        || (Lexer::getImmediateMacroName(
+                loc, compiler.getSourceManager(), compiler.getLangOpts())
+            != "OSL_THIS_FUNC");
+}
+
+loplugin::Plugin::Registration<StringConcatLiterals> stringconcatliterals("stringconcatliterals");
+
+} // namespace
+
+#endif // LO_CLANG_SHARED_PLUGINS
+
+/* vim:set shiftwidth=4 softtabstop=4 expandtab: */