new loplugin:unique2optional

I used this plugin to find places where we could inline a small child
object into a parent object, saving allocation overhead.

Moving it directly into store/ because it is not intended
to be run under normal circumstances, needs hand-holding.

Change-Id: I7245eef3dba187988bb9d4a39fd80624f46355d4
Reviewed-on: https://gerrit.libreoffice.org/c/core/+/148455
Tested-by: Jenkins
Reviewed-by: Noel Grandin <noel.grandin@collabora.co.uk>

1 files changed, 264 insertions, 0 deletions

diff --git a/compilerplugins/clang/store/unique2optional.cxx b/compilerplugins/clang/store/unique2optional.cxx
new file mode 100644
index 000000000000..cc1dc66f193c
--- /dev/null
+++ b/compilerplugins/clang/store/unique2optional.cxx
@@ -0,0 +1,264 @@
+/* -*- 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 <string>
+#include <iostream>
+
+#include "check.hxx"
+#include "plugin.hxx"
+#include "config_clang.h"
+#include "clang/AST/CXXInheritance.h"
+
+/**
+
+Look for places where we are using std::unique_ptr to hold a small object,
+where we should rather be using std::optional.
+
+*/
+
+namespace
+{
+class Unique2Optional : public loplugin::FilteringPlugin<Unique2Optional>
+{
+public:
+    explicit Unique2Optional(loplugin::InstantiationData const& data)
+        : FilteringPlugin(data)
+    {
+    }
+
+    virtual bool preRun() override { return true; }
+
+    virtual void run() override
+    {
+        if (preRun())
+            TraverseDecl(compiler.getASTContext().getTranslationUnitDecl());
+    }
+
+    bool VisitFieldDecl(const FieldDecl*);
+    bool VisitVarDecl(const VarDecl*);
+
+private:
+    bool doDecl(const DeclaratorDecl*);
+    bool isSmall(QualType type);
+};
+
+bool Unique2Optional::VisitFieldDecl(const FieldDecl* fieldDecl) { return doDecl(fieldDecl); }
+bool Unique2Optional::VisitVarDecl(const VarDecl*)
+{
+    return true; //doDecl(varDecl);
+}
+
+bool Unique2Optional::doDecl(const DeclaratorDecl* fieldDecl)
+{
+    if (ignoreLocation(fieldDecl))
+        return true;
+
+    SourceLocation spellingLocation
+        = compiler.getSourceManager().getSpellingLoc(fieldDecl->getBeginLoc());
+    StringRef fileName = getFilenameOfLocation(spellingLocation);
+
+    // pimpl pattern
+    if (loplugin::isSamePathname(fileName, SRCDIR "/include/unotools/closeveto.hxx"))
+        return true;
+    if (loplugin::isSamePathname(fileName, SRCDIR "/include/svl/svdde.hxx"))
+        return true;
+    if (loplugin::isSamePathname(fileName, SRCDIR "/include/vcl/toolkit/morebtn.hxx"))
+        return true;
+    if (loplugin::isSamePathname(fileName, SRCDIR "/include/vcl/toolkit/morebtn.hxx"))
+        return true;
+    if (loplugin::isSamePathname(fileName, SRCDIR "/include/xmloff/xmlexp.hxx"))
+        return true;
+    if (loplugin::isSamePathname(fileName, SRCDIR "/include/xmloff/txtparae.hxx"))
+        return true;
+    if (loplugin::isSamePathname(fileName, SRCDIR "/include/xmloff/controlpropertyhdl.hxx"))
+        return true;
+    if (loplugin::isSamePathname(fileName, SRCDIR "/cui/source/inc/cuitabarea.hxx"))
+        return true;
+
+    // std::type_info is not movable or copyable
+    if (loplugin::isSamePathname(fileName,
+                                 SRCDIR "/bridges/source/cpp_uno/gcc3_linux_x86-64/rtti.cxx"))
+        return true;
+
+    // TODO not sure what is going on here, get a compile error
+    if (loplugin::isSamePathname(fileName, SRCDIR "/vcl/inc/unx/printerjob.hxx"))
+        return true;
+
+    // Seems in bad taste to modify these
+    if (loplugin::isSamePathname(fileName, SRCDIR "/cui/source/tabpages/macroass.cxx"))
+        return true;
+    if (loplugin::isSamePathname(fileName, SRCDIR "/cui/source/inc/cuitabline.hxx"))
+        return true;
+    if (loplugin::isSamePathname(fileName, SRCDIR "/cui/source/inc/page.hxx"))
+        return true;
+    if (loplugin::isSamePathname(fileName, SRCDIR "/sd/source/ui/sidebar/SlideBackground.hxx"))
+        return true;
+    if (loplugin::isSamePathname(fileName, SRCDIR "/hwpfilter/source/nodes.h"))
+        return true;
+    if (loplugin::isSamePathname(fileName, SRCDIR "/hwpfilter/source/hwpfile.h"))
+        return true;
+    if (loplugin::isSamePathname(fileName, SRCDIR "/sw/source/uibase/inc/bookmark.hxx"))
+        return true;
+    if (loplugin::isSamePathname(fileName, SRCDIR "/sw/inc/viewsh.hxx"))
+        return true;
+    if (loplugin::isSamePathname(fileName, SRCDIR "/sw/source/uibase/sidebar/PageFormatPanel.hxx"))
+        return true;
+    if (loplugin::isSamePathname(fileName, SRCDIR "/sw/source/uibase/sidebar/PageStylesPanel.hxx"))
+        return true;
+    if (loplugin::isSamePathname(fileName, SRCDIR "/sc/inc/dpsave.hxx"))
+        return true;
+    if (loplugin::isSamePathname(fileName, SRCDIR "/sc/source/ui/inc/dpgroupdlg.hxx"))
+        return true;
+    if (loplugin::isSamePathname(fileName, SRCDIR "/sc/source/ui/inc/pvfundlg.hxx"))
+        return true;
+    if (loplugin::isSamePathname(fileName, SRCDIR "/sc/inc/document.hxx"))
+        return true;
+    if (loplugin::isSamePathname(fileName, SRCDIR "/sc/inc/scmod.hxx"))
+        return true;
+    if (loplugin::isSamePathname(fileName, SRCDIR "/include/svx/gallery1.hxx"))
+        return true;
+    if (loplugin::isSamePathname(fileName, SRCDIR "/svx/inc/textchainflow.hxx"))
+        return true;
+    if (loplugin::isSamePathname(fileName, SRCDIR "/include/svx/graphctl.hxx"))
+        return true;
+    if (loplugin::isSamePathname(fileName, SRCDIR "/include/svx/float3d.hxx"))
+        return true;
+    if (loplugin::isSamePathname(fileName, SRCDIR "/dbaccess/source/ui/dlg/generalpage.hxx"))
+        return true;
+    if (loplugin::isSamePathname(fileName,
+                                 SRCDIR "/extensions/source/propctrlr/cellbindinghandler.hxx"))
+        return true;
+    if (loplugin::isSamePathname(fileName, SRCDIR "/sc/inc/chartlis.hxx"))
+        return true;
+
+    // header ordering issues make this hard to change
+    if (loplugin::isSamePathname(fileName, SRCDIR "/lotuswordpro/source/filter/lwpdlvlist.hxx"))
+        return true;
+
+    // the classes being allocate are ref-counted
+    if (loplugin::isSamePathname(fileName, SRCDIR "/sc/source/filter/inc/xeextlst.hxx"))
+        return true;
+    if (loplugin::isSamePathname(fileName, SRCDIR "/sc/source/filter/inc/xestyle.hxx"))
+        return true;
+    if (loplugin::isSamePathname(fileName, SRCDIR "/sc/source/ui/inc/tpcalc.hxx"))
+        return true;
+
+    // not sure
+    if (fileName.contains("QtInstance.hxx")) // "/vcl/inc/qt5/QtInstance.hxx"))
+        return true;
+
+    // class is defined inside the module, typically some kind of child/pimpl/listener thing
+    if (loplugin::isSamePathname(fileName, SRCDIR "/include/sfx2/viewfrm.hxx"))
+        return true;
+    if (loplugin::isSamePathname(fileName, SRCDIR "/include/svx/linectrl.hxx"))
+        return true;
+    if (loplugin::isSamePathname(fileName, SRCDIR "/include/svx/sidebar/LinePropertyPanelBase.hxx"))
+        return true;
+    if (loplugin::isSamePathname(fileName, SRCDIR "/vcl/source/fontsubset/ttcr.hxx"))
+        return true;
+    if (loplugin::isSamePathname(fileName,
+                                 SRCDIR "/extensions/source/propctrlr/defaultforminspection.hxx"))
+        return true;
+    if (loplugin::isSamePathname(fileName,
+                                 SRCDIR "/extensions/source/propctrlr/propertyhandler.hxx"))
+        return true;
+    if (loplugin::isSamePathname(fileName, SRCDIR "/sc/inc/spellcheckcontext.hxx"))
+        return true;
+    if (loplugin::isSamePathname(fileName, SRCDIR "/sw/source/core/inc/layouter.hxx"))
+        return true;
+    if (loplugin::isSamePathname(fileName, SRCDIR "/sw/source/uibase/inc/numberingtypelistbox.hxx"))
+        return true;
+    if (loplugin::isSamePathname(fileName, SRCDIR "/lotuswordpro/inc/xfilter/xfdrawstyle.hxx"))
+        return true;
+    if (loplugin::isSamePathname(fileName, SRCDIR "/sc/source/ui/inc/scuiimoptdlg.hxx"))
+        return true;
+
+    // One of the constructors initialises the field by receiving an unique_ptr
+    if (loplugin::isSamePathname(fileName,
+                                 SRCDIR "/lotuswordpro/source/filter/lwpbreaksoverride.hxx"))
+        return true;
+    if (loplugin::isSamePathname(fileName,
+                                 SRCDIR "/lotuswordpro/source/filter/lwpcharborderoverride.hxx"))
+        return true;
+    if (loplugin::isSamePathname(fileName,
+                                 SRCDIR "/lotuswordpro/source/filter/lwpparaborderoverride.hxx"))
+        return true;
+
+    if (!loplugin::TypeCheck(fieldDecl->getType()).ClassOrStruct("unique_ptr").StdNamespace())
+        return true;
+
+    auto templateDecl = dyn_cast_or_null<ClassTemplateSpecializationDecl>(
+        fieldDecl->getType()->getAsRecordDecl());
+    if (!templateDecl)
+        return true;
+    if (templateDecl->getTemplateArgs().size() == 0)
+        return true;
+    auto firstTemplateParamType = templateDecl->getTemplateArgs()[0].getAsType();
+    if (!isSmall(firstTemplateParamType))
+        return true;
+    auto paramRecordDecl = firstTemplateParamType->getAsCXXRecordDecl();
+    if (paramRecordDecl)
+    {
+        // if the pointed-to type has a virtual destructor, then we dont know for sure
+        // what size type will be stored there
+        if (!paramRecordDecl->isEffectivelyFinal())
+            if (CXXDestructorDecl* dd = paramRecordDecl->getDestructor())
+                if (dd->isVirtual())
+                    return true;
+        // If it doesn't have a move constructor, then it would be hard to assign into it
+        // TODO this condition could be relaxed in some situations
+        if (!paramRecordDecl->hasMoveConstructor())
+            return true;
+        // the weld stuff needs to be heap allocated
+        if (loplugin::DeclCheck(paramRecordDecl).Class("CustomWeld").Namespace("weld"))
+            return true;
+        // ref-counted classes should be heap allocated
+        if (loplugin::DeclCheck(paramRecordDecl).Class("SvxContourItem"))
+            return true;
+        if (loplugin::DeclCheck(paramRecordDecl).Class("SvxAdjustItem"))
+            return true;
+        if (loplugin::DeclCheck(paramRecordDecl).Class("SwFormatNoBalancedColumns"))
+            return true;
+        if (loplugin::DeclCheck(paramRecordDecl).Class("SwFormatFollowTextFlow"))
+            return true;
+    }
+    // ignore pimpl pattern
+    if (fieldDecl->getName().contains("pImpl"))
+        return true;
+    if (fieldDecl->getName().contains("impl_"))
+        return true;
+    if (fieldDecl->getName().contains("mxImpl"))
+        return true;
+    if (fieldDecl->getName().contains("m_aImpl"))
+        return true;
+    report(DiagnosticsEngine::Warning, "can use std::optional here, heap-stored type is very small",
+           fieldDecl->getLocation())
+        << fieldDecl->getSourceRange();
+    if (paramRecordDecl)
+        report(DiagnosticsEngine::Note, "class being allocated is here",
+               paramRecordDecl->getLocation())
+            << paramRecordDecl->getSourceRange();
+    return true;
+}
+
+bool Unique2Optional::isSmall(QualType type)
+{
+    if (type->isIncompleteType())
+        return false;
+    clang::Type const* t2 = type.getTypePtrOrNull();
+    if (!t2)
+        return false;
+    // 8 bytes == 1 pointer on 64-bit CPU
+    return compiler.getASTContext().getTypeSizeInChars(t2).getQuantity() <= 16;
+}
+
+loplugin::Plugin::Registration<Unique2Optional> unique2optional("unique2optional");
+}
+
+/* vim:set shiftwidth=4 softtabstop=4 expandtab: */