compilerplugins/clang/sequentialassign.cxx

   1 /* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*- */
   2 /*
   3  * This file is part of the LibreOffice project.
   4  *
   5  * This Source Code Form is subject to the terms of the Mozilla Public
   6  * License, v. 2.0. If a copy of the MPL was not distributed with this
   7  * file, You can obtain one at http://mozilla.org/MPL/2.0/.
   8  */
   9
  10 #include <cassert>
  11 #include <string>
  12 #include <iostream>
  13 #include <unordered_map>
  14 #include <unordered_set>
  15
  16 #include "plugin.hxx"
  17 #include "check.hxx"
  18 #include "clang/AST/CXXInheritance.h"
  19 #include "clang/AST/StmtVisitor.h"
  20
  21 /**
  22     This is a kind of simplified dead-store analysis.
  23
  24     We are looking for patterns like:
  25       Foo x = a;
  26       x = b;
  27     which can be simplified to
  28         x = b
  29
  30     or
  31         Foo x = a;
  32         x = f(x)
  33     which can be simplified to
  34         Foo x = f(a)
  35
  36    TODO Improve this plugin to make it safer. We should really be checking the following
  37    conditions inside the RHS of the second statement:
  38      If the variable is having it's address taken, or a non-const method called on it,
  39      on passed by non-const-ref.
  40 */
  41
  42 namespace
  43 {
  44 //static bool startswith(const std::string& rStr, const char* pSubStr) {
  45 //    return rStr.compare(0, strlen(pSubStr), pSubStr) == 0;
  46 //}
  47 class SequentialAssign : public loplugin::FilteringPlugin<SequentialAssign>
  48 {
  49 public:
  50     explicit SequentialAssign(loplugin::InstantiationData const& data)
  51         : FilteringPlugin(data)
  52     {
  53     }
  54
  55     virtual void run() override
  56     {
  57         std::string fn(handler.getMainFileName());
  58         loplugin::normalizeDotDotInFilePath(fn);
  59         // places where the existing code style just looks better
  60         // TODO lots of these would be unnecessary if I taught the plugin
  61         // to ignore vars which are assigned to repeatedly
  62         if (fn == SRCDIR "/vcl/source/helper/commandinfoprovider.cxx"
  63             || fn == SRCDIR "/basegfx/source/polygon/b2dpolygonclipper.cxx"
  64             || fn == SRCDIR "/i18nlangtag/source/isolang/insys.cxx"
  65             || fn == SRCDIR "/vcl/unx/generic/fontmanager/fontconfig.cxx"
  66             || fn == SRCDIR "/svtools/source/filter/exportdialog.cxx"
  67             || fn == SRCDIR "/svtools/source/control/ruler.cxx"
  68             || fn == SRCDIR "/basic/qa/cppunit/test_scanner.cxx"
  69             || fn == SRCDIR "/basic/source/uno/namecont.cxx"
  70             || fn == SRCDIR "/test/source/sheet/xnamedrange.cxx"
  71             || fn == SRCDIR "/i18npool/qa/cppunit/test_breakiterator.cxx"
  72             || fn == SRCDIR "/i18npool/source/localedata/LocaleNode.cxx"
  73             || fn == SRCDIR "/i18npool/source/transliteration/transliteration_Ignore.cxx"
  74             || fn == SRCDIR "/i18npool/qa/cppunit/test_textsearch.cxx"
  75             || fn == SRCDIR "/framework/source/jobs/jobdata.cxx"
  76             || fn == SRCDIR "/framework/source/services/pathsettings.cxx"
  77             || fn == SRCDIR "/xmloff/source/chart/SchXMLTools.cxx"
  78             || fn == SRCDIR "/svx/source/tbxctrls/Palette.cxx"
  79             || fn == SRCDIR "/svx/source/sdr/contact/objectcontactofpageview.cxx"
  80             || fn == SRCDIR "/svx/source/form/fmservs.cxx"
  81             || fn == SRCDIR "/svx/source/svdraw/svdograf.cxx"
  82             || fn == SRCDIR "/svx/source/accessibility/AccessibleShape.cxx"
  83             || fn == SRCDIR "/svx/source/fmcomp/fmgridcl.cxx"
  84             || fn == SRCDIR "/chart2/source/tools/CharacterProperties.cxx"
  85             || fn == SRCDIR "/svx/source/dialog/dialcontrol.cxx"
  86             || fn == SRCDIR "/connectivity/source/commontools/TTableHelper.cxx"
  87             || fn == SRCDIR "/svx/source/dialog/_bmpmask.cxx"
  88             || fn == SRCDIR "/media/noel/disk2/libo4/cui/source/dialogs/SignSignatureLineDialog.cxx"
  89             || fn == SRCDIR "/filter/source/msfilter/msdffimp.cxx"
  90             || fn == SRCDIR "/filter/source/flash/swffilter.cxx"
  91             || fn == SRCDIR "/cui/source/dialogs/SignSignatureLineDialog.cxx"
  92             || fn == SRCDIR "/cui/source/dialogs/screenshotannotationdlg.cxx"
  93             || fn == SRCDIR "/cui/source/options/optupdt.cxx"
  94             || fn == SRCDIR "/dbaccess/source/ui/querydesign/querycontroller.cxx"
  95             || fn == SRCDIR "/dbaccess/source/ui/dlg/DbAdminImpl.cxx"
  96             || fn == SRCDIR "/dbaccess/source/ui/querydesign/JoinController.cxx"
  97             || fn == SRCDIR "/dbaccess/source/ui/misc/TokenWriter.cxx"
  98             || fn == SRCDIR "/dbaccess/source/ui/misc/TokenWriter.cxx"
  99             || fn == SRCDIR "/dbaccess/source/ui/misc/dbsubcomponentcontroller.cxx"
 100             || fn == SRCDIR "/dbaccess/source/core/api/querycomposer.cxx"
 101             || fn == SRCDIR "/desktop/source/lib/init.cxx"
 102             || fn == SRCDIR "/lotuswordpro/source/filter/lwpfribmark.cxx"
 103             || fn == SRCDIR "/tools/qa/cppunit/test_color.cxx"
 104             || fn == SRCDIR "/sc/qa/unit/ucalc.cxx"
 105             || fn == SRCDIR "/sc/source/ui/view/printfun.cxx"
 106             || fn == SRCDIR "/sc/source/ui/view/preview.cxx"
 107             || fn == SRCDIR "/sw/source/core/doc/tblafmt.cxx"
 108             || fn == SRCDIR "/sw/source/core/draw/dflyobj.cxx"
 109             || fn == SRCDIR "/sw/source/core/doc/DocumentDrawModelManager.cxx"
 110             || fn == SRCDIR "/sw/source/core/edit/edfcol.cxx"
 111             || fn == SRCDIR "/sw/source/filter/ww8/ww8toolbar.cxx"
 112             || fn == SRCDIR "/sw/source/ui/fldui/fldvar.cxx"
 113             || fn == SRCDIR "/sw/source/filter/ww8/ww8atr.cxx"
 114             || fn == SRCDIR "/sd/source/ui/accessibility/AccessiblePageShape.cxx"
 115             || fn == SRCDIR "/xmlsecurity/source/xmlsec/nss/nssinitializer.cxx"
 116             || fn == SRCDIR "/sd/source/ui/slidesorter/cache/SlsRequestFactory.cxx"
 117             || fn == SRCDIR "/sd/source/ui/framework/configuration/ResourceId.cxx"
 118             || fn == SRCDIR "/sd/source/filter/html/htmlex.cxx"
 119             || fn == SRCDIR "/starmath/source/cfgitem.cxx"
 120             || fn == SRCDIR "/ucb/source/ucp/ftp/ftpurl.cxx"
 121             || fn == SRCDIR "/starmath/source/node.cxx"
 122             || fn == SRCDIR "/ucb/source/ucp/cmis/certvalidation_handler.cxx"
 123             || fn == SRCDIR "/reportdesign/source/ui/inspection/GeometryHandler.cxx"
 124             || fn == SRCDIR "/reportdesign/source/core/api/ReportDefinition.cxx"
 125             || fn == SRCDIR "/test/source/table/tablerow.cxx"
 126             || fn == SRCDIR "/basegfx/test/B2DHomMatrixTest.cxx"
 127             || fn == SRCDIR "/comphelper/qa/unit/base64_test.cxx"
 128             || fn == SRCDIR "/testtools/source/bridgetest/bridgetest.cxx"
 129             || fn == SRCDIR "/comphelper/qa/string/test_string.cxx"
 130             || fn == SRCDIR "/cppu/qa/test_unotype.cxx"
 131             || fn == SRCDIR "/cppu/qa/cppumaker/test_cppumaker.cxx"
 132             || fn == SRCDIR "/o3tl/qa/test-lru_map.cxx" || fn == SRCDIR "/svl/qa/unit/svl.cxx"
 133             || fn == SRCDIR "/chart2/qa/extras/PivotChartTest.cxx"
 134             || fn == SRCDIR "/chart2/qa/extras/chart2export.cxx"
 135             || fn == SRCDIR "/writerfilter/qa/cppunittests/misc/misc.cxx"
 136             || fn == SRCDIR "/sw/qa/extras/ww8export/ww8export.cxx"
 137             || fn == SRCDIR "/sw/qa/extras/uiwriter/uiwriter.cxx")
 138             return;
 139         // inside ifdef
 140         if (fn == SRCDIR "/vcl/source/filter/png/pngread.cxx"
 141             || fn == SRCDIR "/vcl/source/window/syschild.cxx"
 142             || fn == SRCDIR "/sal/osl/unx/security.cxx"
 143             || fn == SRCDIR "/vcl/source/filter/png/pngwrite.cxx"
 144             || fn == SRCDIR "/svtools/source/control/inettbc.cxx"
 145             || fn == SRCDIR "/canvas/source/cairo/cairo_textlayout.cxx"
 146             || fn == SRCDIR "/sal/qa/osl/file/osl_File.cxx")
 147             return;
 148         // taking address of variable
 149         if (fn == SRCDIR "/vcl/unx/generic/dtrans/X11_selection.cxx")
 150             return;
 151         // other
 152         if (fn == SRCDIR "/sc/source/core/tool/scmatrix.cxx"
 153             || fn == SRCDIR "/sal/qa/rtl/oustringbuffer/test_oustringbuffer_assign.cxx")
 154             return;
 155
 156         TraverseDecl(compiler.getASTContext().getTranslationUnitDecl());
 157     }
 158
 159     bool VisitCompoundStmt(CompoundStmt const*);
 160
 161 private:
 162     const VarDecl* findSimpleAssign(Stmt const*);
 163     bool isSimpleRHS(Expr const*);
 164     Expr const* ignore(Expr const*);
 165     void checkForSecondAssign(Stmt const* stmt, VarDecl const* varDecl);
 166 };
 167
 168 bool SequentialAssign::VisitCompoundStmt(CompoundStmt const* compoundStmt)
 169 {
 170     if (ignoreLocation(compoundStmt))
 171         return true;
 172
 173     auto it = compoundStmt->body_begin();
 174     while (true)
 175     {
 176         if (it == compoundStmt->body_end())
 177             break;
 178         auto firstStmt = *it;
 179         const VarDecl* foundVars = findSimpleAssign(firstStmt);
 180         // reference types have slightly weird behaviour
 181         if (!foundVars || foundVars->getType()->isReferenceType())
 182         {
 183             ++it;
 184             continue;
 185         }
 186         ++it;
 187         if (it == compoundStmt->body_end())
 188             break;
 189         checkForSecondAssign(*it, foundVars);
 190     }
 191
 192     return true;
 193 }
 194
 195 void SequentialAssign::checkForSecondAssign(Stmt const* stmt, VarDecl const* varDecl)
 196 {
 197     if (auto exprCleanup = dyn_cast<ExprWithCleanups>(stmt))
 198         stmt = exprCleanup->getSubExpr();
 199
 200     if (auto operatorCall = dyn_cast<CXXOperatorCallExpr>(stmt))
 201     {
 202         if (operatorCall->getOperator() == OO_Equal)
 203         {
 204             if (auto declRefExprLHS = dyn_cast<DeclRefExpr>(ignore(operatorCall->getArg(0))))
 205                 if (declRefExprLHS->getDecl() == varDecl)
 206                 {
 207                     report(DiagnosticsEngine::Warning,
 208                            "simplify by merging with the preceding assignment",
 209                            compat::getBeginLoc(stmt))
 210                         << stmt->getSourceRange();
 211                 }
 212         }
 213         return;
 214     }
 215
 216     if (auto binaryOp = dyn_cast<BinaryOperator>(stmt))
 217     {
 218         if (binaryOp->getOpcode() == BO_Assign)
 219         {
 220             if (auto declRefExpr = dyn_cast<DeclRefExpr>(ignore(binaryOp->getLHS())))
 221                 if (declRefExpr->getDecl() == varDecl)
 222                 {
 223                     report(DiagnosticsEngine::Warning,
 224                            "simplify by merging with the preceding assignment",
 225                            compat::getBeginLoc(stmt))
 226                         << stmt->getSourceRange();
 227                 }
 228         }
 229     }
 230 }
 231
 232 const VarDecl* SequentialAssign::findSimpleAssign(Stmt const* stmt)
 233 {
 234     if (auto declStmt = dyn_cast<DeclStmt>(stmt))
 235         if (declStmt->isSingleDecl())
 236             if (auto varDeclLHS = dyn_cast_or_null<VarDecl>(declStmt->getSingleDecl()))
 237             {
 238                 if (varDeclLHS->getStorageDuration() == SD_Static)
 239                     return nullptr;
 240                 // if it's call-style init (e.g. OUString s("xxx")), we only treat
 241                 // it as simple if it only contains a variable in the call
 242                 // (e.g. OUString s(x))
 243                 if (varDeclLHS->getInitStyle() == VarDecl::InitializationStyle::CallInit)
 244                 {
 245                     auto cxxConstructExpr
 246                         = dyn_cast<CXXConstructExpr>(ignore(varDeclLHS->getInit()));
 247                     if (cxxConstructExpr)
 248                     {
 249                         if (cxxConstructExpr->getNumArgs() == 0)
 250                             return varDeclLHS;
 251                         if (cxxConstructExpr->getNumArgs() > 1)
 252                             return nullptr;
 253                         if (!isa<DeclRefExpr>(ignore(cxxConstructExpr->getArg(0))))
 254                             return nullptr;
 255                     }
 256                 }
 257                 if (auto init = varDeclLHS->getInit())
 258                     if (isSimpleRHS(init))
 259                         return varDeclLHS;
 260             }
 261     if (auto operatorCall = dyn_cast<CXXOperatorCallExpr>(stmt))
 262         if (operatorCall->getOperator() == OO_Equal)
 263             if (auto declRefExprLHS = dyn_cast<DeclRefExpr>(ignore(operatorCall->getArg(0))))
 264                 if (auto varDeclLHS = dyn_cast<VarDecl>(declRefExprLHS->getDecl()))
 265                     if (isSimpleRHS(operatorCall->getArg(1)))
 266                         return varDeclLHS;
 267     if (auto binaryOp = dyn_cast<BinaryOperator>(stmt))
 268         if (binaryOp->getOpcode() == BO_Assign)
 269             if (auto declRefExprLHS = dyn_cast<DeclRefExpr>(ignore(binaryOp->getLHS())))
 270                 if (auto varDeclLHS = dyn_cast<VarDecl>(declRefExprLHS->getDecl()))
 271                     if (isSimpleRHS(binaryOp->getRHS()))
 272                         return varDeclLHS;
 273     return nullptr;
 274 }
 275
 276 /**
 277   Does the first statement have a relatively simply RHS we can inline into the second statement?
 278 */
 279 bool SequentialAssign::isSimpleRHS(Expr const* expr)
 280 {
 281     expr = ignore(expr);
 282
 283     // code like
 284     //    Point aCurPos = rGlyphs
 285     // always has a CXXConstructExpr wrapping the RHS
 286     if (auto cxxConstructExpr = dyn_cast<CXXConstructExpr>(expr))
 287         if (cxxConstructExpr->getNumArgs() == 1)
 288             expr = ignore(cxxConstructExpr->getArg(0));
 289
 290     if (!expr->isValueDependent()
 291         && expr->isConstantInitializer(compiler.getASTContext(), false /*ForRef*/))
 292         return true;
 293     if (isa<CXXMemberCallExpr>(expr))
 294         return false;
 295     if (isa<CXXOperatorCallExpr>(expr))
 296         return false;
 297     if (isa<UserDefinedLiteral>(expr))
 298         return true;
 299     if (isa<CallExpr>(expr))
 300         return false;
 301     if (isa<CastExpr>(expr))
 302         return false;
 303     if (isa<ArraySubscriptExpr>(expr))
 304         return false;
 305     if (isa<BinaryOperator>(expr))
 306         return false;
 307     if (isa<ConditionalOperator>(expr))
 308         return false;
 309     if (isa<UnaryOperator>(expr))
 310         return false;
 311     if (isa<CXXNewExpr>(expr))
 312         return false;
 313     if (auto memberExpr = dyn_cast<MemberExpr>(expr))
 314         return isSimpleRHS(memberExpr->getBase());
 315
 316     return true;
 317 }
 318
 319 Expr const* SequentialAssign::ignore(Expr const* expr)
 320 {
 321     return expr->IgnoreImplicit()->IgnoreParens()->IgnoreImplicit();
 322 }
 323
 324 // Off by default because of safety concerns, see TODO at top
 325 loplugin::Plugin::Registration<SequentialAssign> X("sequentialassign", false);
 326 }
 327
 328 /* vim:set shiftwidth=4 softtabstop=4 expandtab: */