new loplugin staticvar

looks for variables that can be declared const and static i.e. they can
be stored in the read-only linker segment and shared between different
processes

Change-Id: I577fb2070604003e56fb44f8a02c9684070311cf
Reviewed-on: https://gerrit.libreoffice.org/61817
Tested-by: Jenkins
Reviewed-by: Noel Grandin <noel.grandin@collabora.co.uk>

2 files changed, 284 insertions, 0 deletions

diff --git a/compilerplugins/clang/staticvar.cxx b/compilerplugins/clang/staticvar.cxx
new file mode 100644
index 000000000000..a9db2f4dda04
--- /dev/null
+++ b/compilerplugins/clang/staticvar.cxx
@@ -0,0 +1,204 @@
+/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*- */
+/*
+ * This file is part of the LibreOffice project.
+ *
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/.
+ */
+
+#include <cassert>
+#include <string>
+#include <iostream>
+#include <unordered_map>
+#include <unordered_set>
+
+#include "plugin.hxx"
+#include "check.hxx"
+#include "clang/AST/CXXInheritance.h"
+#include "clang/AST/StmtVisitor.h"
+
+// Look for variables that either
+// (a) could be statically initialised, without runtime code, and warn
+// (b) variables that are statically declared, but require runtime initialisation, and warn
+//
+// e.g.
+//     static const OUString[] XXX { "xxx" };
+// requires runtime initialisation, so should rather be declared as OUStringLiteral
+// and
+//     static int[] XXX { 1,2 };
+// can be declared const since it does not require runtime initialisation.
+
+namespace
+{
+class StaticVar : public loplugin::FilteringPlugin<StaticVar>
+{
+public:
+    explicit StaticVar(loplugin::InstantiationData const& data)
+        : FilteringPlugin(data)
+    {
+    }
+
+    virtual void run() override
+    {
+        std::string fn(handler.getMainFileName());
+        loplugin::normalizeDotDotInFilePath(fn);
+
+        if (
+            // uses icu::UnicodeString
+            fn == SRCDIR "/l10ntools/source/xmlparse.cxx"
+            // contains mutable state
+            || fn == SRCDIR "/sal/osl/unx/signal.cxx"
+            || fn == SRCDIR "/sal/qa/rtl/digest/rtl_digest.cxx"
+            || fn == SRCDIR "/sal/qa/rtl/strings/test_oustring_endswith.cxx"
+            || fn == SRCDIR "/sal/qa/rtl/strings/test_oustring_convert.cxx"
+            || fn == SRCDIR "/svl/qa/unit/items/test_itempool.cxx"
+            // contains mutable state
+            || fn == SRCDIR "/vcl/unx/generic/dtrans/X11_selection.cxx"
+            || fn == SRCDIR "/sax/qa/cppunit/xmlimport.cxx"
+            || fn == SRCDIR "/pyuno/source/module/pyuno.cxx"
+            || fn == SRCDIR "/pyuno/source/module/pyuno_module.cxx"
+            || fn == SRCDIR "/pyuno/source/module/pyuno_struct.cxx"
+            // TODO for this one we need a static OUString
+            || fn == SRCDIR "/xmloff/source/core/xmltoken.cxx"
+            // mutable
+            || fn == SRCDIR "/basic/source/runtime/stdobj.cxx"
+            // TODO this needs more extensive cleanup
+            || fn == SRCDIR "/connectivity/source/drivers/postgresql/pq_statics.cxx"
+            // mutable
+            || fn == SRCDIR "/hwpfilter/source/hwpreader.cxx"
+            // mutable
+            || fn == SRCDIR "/sw/source/filter/basflt/fltini.cxx"
+            // mutable
+            || fn == SRCDIR "/sw/source/uibase/docvw/srcedtw.cxx"
+            // mutable
+            || fn == SRCDIR "/forms/source/misc/limitedformats.cxx"
+            // aHTMLOptionTab is ordered by useful grouping, so let it sort at runtime
+            || fn == SRCDIR "/svtools/source/svhtml/htmlkywd.cxx"
+            // TODO sorting some of these tables will be a lot of work...
+            || fn == SRCDIR "/sw/source/filter/ww8/ww8par6.cxx")
+            return;
+        TraverseDecl(compiler.getASTContext().getTranslationUnitDecl());
+    }
+
+    bool VisitVarDecl(VarDecl const*);
+};
+
+static bool containsNonLiteral(Expr const* expr)
+{
+    expr = expr->IgnoreImplicit();
+    if (auto initList = dyn_cast<InitListExpr>(expr))
+    {
+        for (unsigned i = 0; i < initList->getNumInits(); ++i)
+            if (containsNonLiteral(initList->getInit(i)))
+                return true;
+    }
+    else if (auto constructExpr = dyn_cast<CXXConstructExpr>(expr))
+    {
+        for (Expr const* arg : constructExpr->arguments())
+            if (containsNonLiteral(arg))
+                return true;
+    }
+    else if (isa<MemberExpr>(expr))
+        return true;
+    else if (auto declRefExpr = dyn_cast<DeclRefExpr>(expr))
+    {
+        auto varDecl = dyn_cast_or_null<VarDecl>(declRefExpr->getDecl());
+        return varDecl && varDecl->isLocalVarDeclOrParm();
+    }
+    else if (isa<CXXMemberCallExpr>(expr))
+        return true;
+    else if (auto castExpr = dyn_cast<CXXFunctionalCastExpr>(expr))
+        return containsNonLiteral(castExpr->getSubExpr());
+    else if (auto unaryOp = dyn_cast<UnaryOperator>(expr))
+        return containsNonLiteral(unaryOp->getSubExpr());
+
+    return false;
+}
+
+bool StaticVar::VisitVarDecl(VarDecl const* varDecl)
+{
+    if (ignoreLocation(varDecl))
+        return true;
+    if (!varDecl->hasInit())
+        return true;
+    auto initList = dyn_cast_or_null<InitListExpr>(varDecl->getInit());
+    if (!initList)
+        return true;
+    if (varDecl->isExceptionVariable() || isa<ParmVarDecl>(varDecl))
+        return true;
+    if (!varDecl->getType()->isArrayType())
+        return true;
+    auto elementType = varDecl->getType()->getBaseElementTypeUnsafe();
+    if (!elementType->isRecordType())
+        return true;
+    auto elementRecordDecl
+        = dyn_cast_or_null<CXXRecordDecl>(elementType->getAs<RecordType>()->getDecl());
+    if (!elementRecordDecl)
+        return true;
+    if (containsNonLiteral(initList))
+        return true;
+
+    if (elementRecordDecl->hasTrivialDestructor())
+    {
+        if (varDecl->isLocalVarDecl())
+        {
+            if (varDecl->getStorageDuration() == SD_Static && varDecl->getType().isConstQualified())
+                return true;
+        }
+        else
+        {
+            if (varDecl->getType().isConstQualified())
+                return true;
+        }
+
+        // TODO cannot figure out how to make the loplugin::TypeCheck stuff match this
+        //    std::string typeName = varDecl->getType().getAsString();
+        //    if (typeName == "std::va_list" || typeName == "va_list")
+        //        return true;
+
+        auto const tcElement = loplugin::TypeCheck(elementRecordDecl);
+        if (tcElement.Struct("ContextID_Index_Pair").GlobalNamespace())
+            return true;
+        if (tcElement.Class("SfxSlot").GlobalNamespace())
+            return true;
+
+        if (varDecl->isLocalVarDecl())
+            report(DiagnosticsEngine::Warning, "var should be static const, or whitelisted",
+                   varDecl->getLocation())
+                << varDecl->getSourceRange();
+        else
+            report(DiagnosticsEngine::Warning, "var should be const, or whitelisted",
+                   varDecl->getLocation())
+                << varDecl->getSourceRange();
+    }
+    else
+    {
+        if (varDecl->isLocalVarDecl())
+        {
+            if (varDecl->getStorageDuration() != SD_Static
+                || !varDecl->getType().isConstQualified())
+                return true;
+        }
+        else
+        {
+            if (!varDecl->getType().isConstQualified())
+                return true;
+        }
+
+        if (varDecl->isLocalVarDecl())
+            report(DiagnosticsEngine::Warning, "static const var requires runtime initialization?",
+                   varDecl->getLocation())
+                << varDecl->getSourceRange();
+        else
+            report(DiagnosticsEngine::Warning, "static var requires runtime initialization?",
+                   varDecl->getLocation())
+                << varDecl->getSourceRange();
+    }
+    return true;
+}
+
+loplugin::Plugin::Registration<StaticVar> X("staticvar", false);
+}
+
+/* vim:set shiftwidth=4 softtabstop=4 expandtab: */
diff --git a/compilerplugins/clang/test/staticvar.cxx b/compilerplugins/clang/test/staticvar.cxx
new file mode 100644
index 000000000000..9963e99db687
--- /dev/null
+++ b/compilerplugins/clang/test/staticvar.cxx
@@ -0,0 +1,80 @@
+/* -*- 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 <config_clang.h>
+#include <sal/config.h>
+#include <rtl/ustring.hxx>
+
+struct S1
+{
+    int x, y;
+};
+
+S1 const& f1(int a)
+{
+    static S1 s1[]{
+        // expected-error@-1 {{var should be static const, or whitelisted [loplugin:staticvar]}}
+        { 1, 1 }
+    };
+    // no warning expected
+    const S1 s2[]{ { a, 1 } };
+    (void)s2;
+    return s1[0];
+}
+
+struct S2
+{
+    OUString x;
+};
+
+#if CLANG_VERSION >= 50000 // probably something to do with how OUString initialisers work
+S2 const& f2()
+{
+    static S2 const s1[]{
+        // expected-error@-1 {{static const var requires runtime initialization? [loplugin:staticvar]}}
+        { "xxx" }
+    };
+    return s1[0];
+}
+#endif
+
+// no warning expected
+S2 const& f3()
+{
+    static S2 s1[]{ { "xxx" } };
+    return s1[0];
+}
+
+// no warning expected
+struct S4
+{
+    OUStringLiteral const cName;
+    bool const bCanBeVisible;
+};
+S4 const& f4()
+{
+    static const S4 s1[] = {
+        { OUStringLiteral("/DocColor"), false },
+    };
+    return s1[0];
+}
+
+struct S5
+{
+    bool const bCanBeVisible;
+};
+void f5(bool b)
+{
+    const S5 s1[] = {
+        { b },
+    };
+    (void)s1;
+}
+
+/* vim:set shiftwidth=4 softtabstop=4 expandtab cinoptions=b1,g0,N-s cinkeys+=0=break: */