New loplugin:stringliteralvar

See the comment at the top of compilerplugins/clang/stringliteralvar.cxx for
details.

(Turned some affected variables in included files into inline variables, to
avoid GCC warnings about unused variables.)

Change-Id: Ie77219e6adfdaaceaa8b4e590b08971f2f04c83a
Reviewed-on: https://gerrit.libreoffice.org/c/core/+/108239
Tested-by: Jenkins
Reviewed-by: Stephan Bergmann <sbergman@redhat.com>

2 files changed, 284 insertions, 0 deletions

diff --git a/compilerplugins/clang/stringliteralvar.cxx b/compilerplugins/clang/stringliteralvar.cxx
new file mode 100644
index 000000000000..348193421a61
--- /dev/null
+++ b/compilerplugins/clang/stringliteralvar.cxx
@@ -0,0 +1,203 @@
+/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4; fill-column: 100 -*- */
+/*
+ * This file is part of the LibreOffice project.
+ *
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/.
+ */
+
+// Find constant character array variables that are passed into O[U]String constructors and should
+// thus be turned into O[U]StringLiteral variables.
+//
+// Such a variable may have been used in multiple places, not all of which would be compatible with
+// changing the variable's type to O[U]StringLiteral.  However, this plugin is aggressive and
+// ignores all but the first use of such a variable.  In all cases of incompatible uses so far, it
+// was possible to change to surrounding code (for the better) to make the changes work.
+//
+// The plugin also flags O[U]StringLiteral variables of automatic storage duration, and uses of such
+// variables with sizeof---two likely errors that can occur once a variable has been changed from a
+// character array to O[U]StringLiteral.
+//
+//TODO:  In theory, we should not only look for variables, but also for non-static data members.  In
+// practice, those should be rare, though, as they should arguably have been static data members to
+// begin with.
+
+#include <cassert>
+
+#include "check.hxx"
+#include "plugin.hxx"
+
+namespace
+{
+bool isAutomaticVariable(VarDecl const* decl)
+{
+    switch (cast<VarDecl>(decl)->getStorageDuration())
+    {
+        case SD_Automatic:
+            return true;
+        case SD_Thread:
+        case SD_Static:
+            return false;
+        case SD_FullExpression:
+        case SD_Dynamic:
+            assert(false);
+        default:
+            llvm_unreachable("unknown StorageDuration");
+    }
+}
+
+class StringLiteralVar final : public loplugin::FilteringPlugin<StringLiteralVar>
+{
+public:
+    explicit StringLiteralVar(loplugin::InstantiationData const& data)
+        : FilteringPlugin(data)
+    {
+    }
+
+    bool TraverseInitListExpr(InitListExpr* expr, DataRecursionQueue* queue = nullptr)
+    {
+        return WalkUpFromInitListExpr(expr)
+               && TraverseSynOrSemInitListExpr(
+                      expr->isSemanticForm() ? expr : expr->getSemanticForm(), queue);
+    }
+
+    bool VisitCXXConstructExpr(CXXConstructExpr const* expr)
+    {
+        if (ignoreLocation(expr))
+        {
+            return true;
+        }
+        loplugin::TypeCheck const tc(expr->getType());
+        if (!(tc.Class("OString").Namespace("rtl").GlobalNamespace()
+              || tc.Class("OUString").Namespace("rtl").GlobalNamespace()))
+        {
+            return true;
+        }
+        switch (expr->getConstructor()->getNumParams())
+        {
+            case 1:
+            {
+                auto const e = dyn_cast<DeclRefExpr>(expr->getArg(0)->IgnoreParenImpCasts());
+                if (e == nullptr)
+                {
+                    return true;
+                }
+                auto const tc = loplugin::TypeCheck(e->getType());
+                if (!(tc.Class("OStringLiteral").Namespace("rtl").GlobalNamespace()
+                      || tc.Class("OUStringLiteral").Namespace("rtl").GlobalNamespace()))
+                {
+                    return true;
+                }
+                auto const d = e->getDecl();
+                if (!isAutomaticVariable(cast<VarDecl>(d)))
+                {
+                    return true;
+                }
+                if (!reportedAutomatic_.insert(d).second)
+                {
+                    return true;
+                }
+                report(DiagnosticsEngine::Warning,
+                       "variable %0 of type %1 with automatic storage duration most likely needs "
+                       "to be static",
+                       d->getLocation())
+                    << d << d->getType() << d->getSourceRange();
+                report(DiagnosticsEngine::Note, "first converted to %0 here", expr->getLocation())
+                    << expr->getType() << expr->getSourceRange();
+            }
+            break;
+            case 2:
+            {
+                auto const e1 = dyn_cast<DeclRefExpr>(expr->getArg(0)->IgnoreParenImpCasts());
+                if (e1 == nullptr)
+                {
+                    return true;
+                }
+                auto const t = e1->getType();
+                if (!(t.isConstQualified() && t->isConstantArrayType()))
+                {
+                    return true;
+                }
+                auto const e2 = expr->getArg(1);
+                if (!(isa<CXXDefaultArgExpr>(e2)
+                      && loplugin::TypeCheck(e2->getType())
+                             .Struct("Dummy")
+                             .Namespace("libreoffice_internal")
+                             .Namespace("rtl")
+                             .GlobalNamespace()))
+                {
+                    return true;
+                }
+                auto const d = e1->getDecl();
+                if (!reportedArray_.insert(d).second)
+                {
+                    return true;
+                }
+                report(DiagnosticsEngine::Warning,
+                       "change type of variable %0 from constant character array (%1) to "
+                       "%select{OStringLiteral|OUStringLiteral}2%select{|, and make it static}3",
+                       d->getLocation())
+                    << d << d->getType()
+                    << (tc.Class("OString").Namespace("rtl").GlobalNamespace() ? 0 : 1)
+                    << isAutomaticVariable(cast<VarDecl>(d)) << d->getSourceRange();
+                report(DiagnosticsEngine::Note, "first passed into a %0 constructor here",
+                       expr->getLocation())
+                    << expr->getType().getUnqualifiedType() << expr->getSourceRange();
+            }
+            break;
+        }
+        return true;
+    }
+
+    bool VisitUnaryExprOrTypeTraitExpr(UnaryExprOrTypeTraitExpr const* expr)
+    {
+        if (ignoreLocation(expr))
+        {
+            return true;
+        }
+        if (expr->getKind() != UETT_SizeOf)
+        {
+            return true;
+        }
+        if (expr->isArgumentType())
+        {
+            return true;
+        }
+        auto const e = dyn_cast<DeclRefExpr>(expr->getArgumentExpr()->IgnoreParenImpCasts());
+        if (e == nullptr)
+        {
+            return true;
+        }
+        auto const tc = loplugin::TypeCheck(e->getType());
+        if (!(tc.Class("OStringLiteral").Namespace("rtl").GlobalNamespace()
+              || tc.Class("OUStringLiteral").Namespace("rtl").GlobalNamespace()))
+        {
+            return true;
+        }
+        auto const d = e->getDecl();
+        report(DiagnosticsEngine::Warning,
+               "variable %0 of type %1 suspiciously used in a sizeof expression", e->getLocation())
+            << d << d->getType() << expr->getSourceRange();
+        return true;
+    }
+
+    bool preRun() override { return compiler.getLangOpts().CPlusPlus; }
+
+private:
+    void run() override
+    {
+        if (preRun())
+        {
+            TraverseDecl(compiler.getASTContext().getTranslationUnitDecl());
+        }
+    }
+
+    std::set<Decl const*> reportedAutomatic_;
+    std::set<Decl const*> reportedArray_;
+};
+
+static loplugin::Plugin::Registration<StringLiteralVar> reg("stringliteralvar");
+}
+
+/* vim:set shiftwidth=4 softtabstop=4 expandtab cinoptions=b1,g0,N-s cinkeys+=0=break: */
diff --git a/compilerplugins/clang/test/stringliteralvar.cxx b/compilerplugins/clang/test/stringliteralvar.cxx
new file mode 100644
index 000000000000..25a85f90a5a3
--- /dev/null
+++ b/compilerplugins/clang/test/stringliteralvar.cxx
@@ -0,0 +1,81 @@
+/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4; fill-column: 100 -*- */
+/*
+ * This file is part of the LibreOffice project.
+ *
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/.
+ */
+
+#include <sal/config.h>
+
+#include <vector>
+
+#include <rtl/ustring.hxx>
+
+// expected-error@+1 {{change type of variable 'literal1' from constant character array ('const char [4]') to OStringLiteral [loplugin:stringliteralvar]}}
+char const literal1[] = "foo";
+OString f1()
+{
+    // expected-note@+1 {{first passed into a 'rtl::OString' constructor here [loplugin:stringliteralvar]}}
+    return literal1;
+}
+
+void f(OUString const&);
+void f2()
+{
+    // expected-error@+1 {{change type of variable 'literal' from constant character array ('const char [4]') to OUStringLiteral, and make it static [loplugin:stringliteralvar]}}
+    char const literal[] = "foo";
+    // expected-note@+1 {{first passed into a 'rtl::OUString' constructor here [loplugin:stringliteralvar]}}
+    f(literal);
+}
+
+struct S3
+{
+    // expected-error@+1 {{change type of variable 'literal' from constant character array ('const char16_t [4]') to OUStringLiteral [loplugin:stringliteralvar]}}
+    static constexpr char16_t literal[] = u"foo";
+};
+void f3()
+{
+    // expected-note@+1 {{first passed into a 'rtl::OUString' constructor here [loplugin:stringliteralvar]}}
+    f(S3::literal);
+}
+
+std::vector<OUString> f4()
+{
+    // expected-error@+1 {{change type of variable 'literal' from constant character array ('const char16_t [4]') to OUStringLiteral [loplugin:stringliteralvar]}}
+    static constexpr char16_t literal[] = u"foo";
+    // expected-note@+1 {{first passed into a 'rtl::OUString' constructor here [loplugin:stringliteralvar]}}
+    return { literal };
+}
+
+void f5()
+{
+    // expected-error@+1 {{variable 'literal' of type 'const rtl::OUStringLiteral<4>' with automatic storage duration most likely needs to be static [loplugin:stringliteralvar]}}
+    OUStringLiteral const literal = u"foo";
+    // expected-note@+1 {{first converted to 'rtl::OUString' here [loplugin:stringliteralvar]}}
+    f(literal);
+}
+
+void f6()
+{
+    // expected-error@+1 {{variable 'literal' of type 'const rtl::OUStringLiteral<4>' with automatic storage duration most likely needs to be static [loplugin:stringliteralvar]}}
+    constexpr OUStringLiteral literal = u"foo";
+    // expected-note@+1 {{first converted to 'rtl::OUString' here [loplugin:stringliteralvar]}}
+    f(literal);
+}
+
+void f7()
+{
+    static constexpr OUStringLiteral const literal = u"foo";
+    f(literal);
+}
+
+void f8()
+{
+    static constexpr OUStringLiteral const literal = u"foo";
+    // expected-error@+1 {{variable 'literal' of type 'const rtl::OUStringLiteral<4>' suspiciously used in a sizeof expression [loplugin:stringliteralvar]}}
+    (void)sizeof literal;
+}
+
+/* vim:set shiftwidth=4 softtabstop=4 expandtab cinoptions=b1,g0,N-s cinkeys+=0=break: */