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-rw-r--r--compilerplugins/clang/reducevarscope.cxx551
1 files changed, 551 insertions, 0 deletions
diff --git a/compilerplugins/clang/reducevarscope.cxx b/compilerplugins/clang/reducevarscope.cxx
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+++ b/compilerplugins/clang/reducevarscope.cxx
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+/* -*- 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 <map>
+#include <set>
+#include <vector>
+#include <unordered_map>
+#include <unordered_set>
+
+#include "plugin.hxx"
+#include "check.hxx"
+#include "config_clang.h"
+#include "clang/AST/CXXInheritance.h"
+#include "clang/AST/StmtVisitor.h"
+
+// Original idea from mike kaganski.
+// Look for variables that can have their scoped reduced, which makes the code easier to read.
+
+// TODO when dealing with vars that are referenced in multiple child blocks, the check is very primitive
+// and could be greatly improved.
+
+namespace
+{
+class ReduceVarScope : public loplugin::FilteringPlugin<ReduceVarScope>
+{
+public:
+ explicit ReduceVarScope(loplugin::InstantiationData const& data)
+ : FilteringPlugin(data)
+ {
+ }
+
+ bool preRun() override
+ {
+ if (!compiler.getLangOpts().CPlusPlus)
+ return false;
+ // ignore some files with problematic macros
+ std::string fn(handler.getMainFileName());
+ loplugin::normalizeDotDotInFilePath(fn);
+ // some declarations look better all together
+ if (fn == SRCDIR "/package/source/manifest/ManifestExport.cxx")
+ return false;
+ // storing pointer to OUString internal data
+ if (fn == SRCDIR "/connectivity/source/drivers/odbc/ODatabaseMetaDataResultSet.cxx"
+ || fn == SRCDIR "/sc/source/filter/excel/xestyle.cxx"
+ || fn == SRCDIR "/sw/source/filter/html/htmlflywriter.cxx"
+ || fn == SRCDIR "/unoxml/source/dom/element.cxx"
+ || fn == SRCDIR "/unoxml/source/dom/document.cxx"
+ || fn == SRCDIR "/sd/source/filter/eppt/pptx-animations.cxx")
+ return false;
+ if (fn == SRCDIR "/sal/qa/rtl/strings/nonconstarray.cxx")
+ return false;
+ return true;
+ }
+
+ virtual void run() override
+ {
+ if (!preRun())
+ return;
+
+ TraverseDecl(compiler.getASTContext().getTranslationUnitDecl());
+ postRun();
+ }
+
+ virtual void postRun() override
+ {
+ for (auto const& pair : maVarDeclMap)
+ {
+ auto varDecl = pair.first;
+ auto const& depthInfo = pair.second;
+ if (depthInfo.maDeclBlockPath.size() == depthInfo.maCommonBlockPath.size())
+ continue;
+ if (maVarDeclToIgnoreSet.find(varDecl) != maVarDeclToIgnoreSet.end())
+ continue;
+ auto it = maVarUseSourceRangeMap.find(varDecl);
+ if (it == maVarUseSourceRangeMap.end())
+ continue;
+ report(DiagnosticsEngine::Warning, "can reduce scope of var", varDecl->getLocation())
+ << varDecl->getSourceRange();
+ for (SourceRange const& useRange : it->second)
+ report(DiagnosticsEngine::Note, "used here", useRange.getBegin()) << useRange;
+ }
+ }
+
+ bool VisitUnaryOperator(UnaryOperator const* expr)
+ {
+ // if we take the address of it
+ UnaryOperator::Opcode op = expr->getOpcode();
+ if (op == UO_AddrOf)
+ recordIgnore(expr->getSubExpr());
+ return true;
+ }
+
+ bool VisitDeclRefExpr(const DeclRefExpr*);
+ bool VisitVarDecl(const VarDecl*);
+ bool VisitLambdaExpr(const LambdaExpr*);
+
+ bool PreTraverseFunctionDecl(FunctionDecl*);
+ bool PostTraverseFunctionDecl(FunctionDecl*, bool);
+ bool TraverseFunctionDecl(FunctionDecl*);
+
+ bool PreTraverseCompoundStmt(CompoundStmt*);
+ bool PostTraverseCompoundStmt(CompoundStmt*, bool);
+ bool TraverseCompoundStmt(CompoundStmt*);
+
+ bool PreTraverseWhileStmt(WhileStmt*);
+ bool PostTraverseWhileStmt(WhileStmt*, bool);
+ bool TraverseWhileStmt(WhileStmt*);
+
+ bool PreTraverseDoStmt(DoStmt*);
+ bool PostTraverseDoStmt(DoStmt*, bool);
+ bool TraverseDoStmt(DoStmt*);
+
+ bool PreTraverseCXXForRangeStmt(CXXForRangeStmt*);
+ bool PostTraverseCXXForRangeStmt(CXXForRangeStmt*, bool);
+ bool TraverseCXXForRangeStmt(CXXForRangeStmt*);
+
+ bool PreTraverseForStmt(ForStmt*);
+ bool PostTraverseForStmt(ForStmt*, bool);
+ bool TraverseForStmt(ForStmt*);
+
+ bool PreTraverseSwitchStmt(SwitchStmt*);
+ bool PostTraverseSwitchStmt(SwitchStmt*, bool);
+ bool TraverseSwitchStmt(SwitchStmt*);
+
+private:
+ struct DepthInfo
+ {
+ unsigned int mnFirstDepth = 0;
+ unsigned int mnFirstLoopDepth = 0;
+ std::vector<unsigned int> maDeclBlockPath = {};
+ std::vector<unsigned int> maCommonBlockPath = {};
+ };
+ std::unordered_map<VarDecl const*, DepthInfo> maVarDeclMap; // varDecl->depth
+ std::unordered_set<VarDecl const*> maVarDeclToIgnoreSet;
+ std::map<VarDecl const*, std::vector<SourceRange>> maVarUseSourceRangeMap;
+ std::vector<unsigned int> maCurrentBlockPath;
+ unsigned int mnCurrentDepth = 0;
+ unsigned int mnCurrentLoopDepth = 0;
+ static unsigned int gnBlockId;
+
+ bool isTypeOK(QualType qt);
+ bool isInitConstant(const VarDecl* varDecl);
+
+ void recordIgnore(Expr const* expr)
+ {
+ for (;;)
+ {
+ expr = expr->IgnoreParenImpCasts();
+ if (auto const e = dyn_cast<MemberExpr>(expr))
+ {
+ if (isa<FieldDecl>(e->getMemberDecl()))
+ {
+ expr = e->getBase();
+ continue;
+ }
+ }
+ if (auto const e = dyn_cast<ArraySubscriptExpr>(expr))
+ {
+ expr = e->getBase();
+ continue;
+ }
+ if (auto const e = dyn_cast<BinaryOperator>(expr))
+ {
+ if (e->getOpcode() == BO_PtrMemD)
+ {
+ expr = e->getLHS();
+ continue;
+ }
+ }
+ break;
+ }
+ auto const dre = dyn_cast<DeclRefExpr>(expr);
+ if (dre == nullptr)
+ return;
+ auto const var = dyn_cast<VarDecl>(dre->getDecl());
+ if (var == nullptr)
+ return;
+ maVarDeclToIgnoreSet.insert(var);
+ }
+};
+
+unsigned int ReduceVarScope::gnBlockId = 0;
+
+bool ReduceVarScope::PreTraverseFunctionDecl(FunctionDecl* functionDecl)
+{
+ // Ignore functions that contains #ifdef-ery, can be quite tricky
+ // to make useful changes when this plugin fires in such functions
+ if (containsPreprocessingConditionalInclusion(functionDecl->getSourceRange()))
+ return false;
+ return true;
+}
+
+bool ReduceVarScope::PostTraverseFunctionDecl(FunctionDecl*, bool) { return true; }
+
+bool ReduceVarScope::TraverseFunctionDecl(FunctionDecl* functionDecl)
+{
+ bool ret = true;
+ if (PreTraverseFunctionDecl(functionDecl))
+ {
+ ret = FilteringPlugin::TraverseFunctionDecl(functionDecl);
+ PostTraverseFunctionDecl(functionDecl, ret);
+ }
+ return ret;
+}
+
+bool ReduceVarScope::PreTraverseCompoundStmt(CompoundStmt*)
+{
+ assert(mnCurrentDepth != std::numeric_limits<unsigned int>::max());
+ ++mnCurrentDepth;
+ ++gnBlockId;
+ maCurrentBlockPath.push_back(gnBlockId);
+ return true;
+}
+
+bool ReduceVarScope::PostTraverseCompoundStmt(CompoundStmt*, bool)
+{
+ assert(mnCurrentDepth != 0);
+ --mnCurrentDepth;
+ maCurrentBlockPath.pop_back();
+ return true;
+}
+
+bool ReduceVarScope::TraverseCompoundStmt(CompoundStmt* decl)
+{
+ bool ret = true;
+ if (PreTraverseCompoundStmt(decl))
+ {
+ ret = FilteringPlugin::TraverseCompoundStmt(decl);
+ PostTraverseCompoundStmt(decl, ret);
+ }
+ return ret;
+}
+
+bool ReduceVarScope::PreTraverseWhileStmt(WhileStmt*)
+{
+ assert(mnCurrentLoopDepth != std::numeric_limits<unsigned int>::max());
+ ++mnCurrentLoopDepth;
+ return true;
+}
+
+bool ReduceVarScope::PostTraverseWhileStmt(WhileStmt*, bool)
+{
+ assert(mnCurrentLoopDepth != 0);
+ --mnCurrentLoopDepth;
+ return true;
+}
+
+bool ReduceVarScope::TraverseWhileStmt(WhileStmt* decl)
+{
+ bool ret = true;
+ if (PreTraverseWhileStmt(decl))
+ {
+ ret = FilteringPlugin::TraverseWhileStmt(decl);
+ PostTraverseWhileStmt(decl, ret);
+ }
+ return ret;
+}
+
+bool ReduceVarScope::PreTraverseDoStmt(DoStmt*)
+{
+ assert(mnCurrentLoopDepth != std::numeric_limits<unsigned int>::max());
+ ++mnCurrentLoopDepth;
+ return true;
+}
+
+bool ReduceVarScope::PostTraverseDoStmt(DoStmt*, bool)
+{
+ assert(mnCurrentLoopDepth != 0);
+ --mnCurrentLoopDepth;
+ return true;
+}
+
+bool ReduceVarScope::TraverseDoStmt(DoStmt* decl)
+{
+ bool ret = true;
+ if (PreTraverseDoStmt(decl))
+ {
+ ret = FilteringPlugin::TraverseDoStmt(decl);
+ PostTraverseDoStmt(decl, ret);
+ }
+ return ret;
+}
+
+bool ReduceVarScope::PreTraverseSwitchStmt(SwitchStmt*)
+{
+ assert(mnCurrentLoopDepth != std::numeric_limits<unsigned int>::max());
+ ++mnCurrentLoopDepth;
+ return true;
+}
+
+bool ReduceVarScope::PostTraverseSwitchStmt(SwitchStmt*, bool)
+{
+ assert(mnCurrentLoopDepth != 0);
+ --mnCurrentLoopDepth;
+ return true;
+}
+
+// Consider a switch to be a loop, because weird things happen inside it
+bool ReduceVarScope::TraverseSwitchStmt(SwitchStmt* decl)
+{
+ bool ret = true;
+ if (PreTraverseSwitchStmt(decl))
+ {
+ ret = FilteringPlugin::TraverseSwitchStmt(decl);
+ PostTraverseSwitchStmt(decl, ret);
+ }
+ return ret;
+}
+
+bool ReduceVarScope::PreTraverseCXXForRangeStmt(CXXForRangeStmt*)
+{
+ assert(mnCurrentLoopDepth != std::numeric_limits<unsigned int>::max());
+ ++mnCurrentLoopDepth;
+ return true;
+}
+
+bool ReduceVarScope::PostTraverseCXXForRangeStmt(CXXForRangeStmt*, bool)
+{
+ assert(mnCurrentLoopDepth != 0);
+ --mnCurrentLoopDepth;
+ return true;
+}
+
+bool ReduceVarScope::TraverseCXXForRangeStmt(CXXForRangeStmt* decl)
+{
+ bool ret = true;
+ if (PreTraverseCXXForRangeStmt(decl))
+ {
+ ret = FilteringPlugin::TraverseCXXForRangeStmt(decl);
+ PostTraverseCXXForRangeStmt(decl, ret);
+ }
+ return ret;
+}
+
+bool ReduceVarScope::PreTraverseForStmt(ForStmt* forStmt)
+{
+ assert(mnCurrentLoopDepth != std::numeric_limits<unsigned int>::max());
+ ++mnCurrentLoopDepth;
+
+ auto declStmt = dyn_cast_or_null<DeclStmt>(forStmt->getInit());
+ if (declStmt)
+ {
+ if (declStmt->isSingleDecl())
+ {
+ if (auto varDecl = dyn_cast_or_null<VarDecl>(declStmt->getSingleDecl()))
+ maVarDeclToIgnoreSet.insert(varDecl);
+ }
+ else
+ {
+ for (auto const& decl : declStmt->getDeclGroup())
+ if (auto varDecl = dyn_cast_or_null<VarDecl>(decl))
+ maVarDeclToIgnoreSet.insert(varDecl);
+ }
+ }
+
+ return true;
+}
+
+bool ReduceVarScope::PostTraverseForStmt(ForStmt*, bool)
+{
+ assert(mnCurrentLoopDepth != 0);
+ --mnCurrentLoopDepth;
+ return true;
+}
+
+bool ReduceVarScope::TraverseForStmt(ForStmt* decl)
+{
+ bool ret = true;
+ if (PreTraverseForStmt(decl))
+ {
+ ret = FilteringPlugin::TraverseForStmt(decl);
+ PostTraverseForStmt(decl, ret);
+ }
+ return ret;
+}
+
+bool ReduceVarScope::VisitVarDecl(const VarDecl* varDecl)
+{
+ if (ignoreLocation(varDecl))
+ return true;
+ if (varDecl->isExceptionVariable() || isa<ParmVarDecl>(varDecl))
+ return true;
+ // ignore stuff in header files (which should really not be there, but anyhow)
+ if (!compiler.getSourceManager().isInMainFile(varDecl->getLocation()))
+ return true;
+ // Ignore macros like FD_ZERO
+ if (compiler.getSourceManager().isMacroBodyExpansion(varDecl->getBeginLoc()))
+ return true;
+ if (varDecl->hasGlobalStorage())
+ return true;
+ if (varDecl->isConstexpr())
+ return true;
+ if (varDecl->isInitCapture())
+ return true;
+ if (varDecl->isCXXForRangeDecl())
+ return true;
+ if (!isTypeOK(varDecl->getType()))
+ return true;
+
+ if (varDecl->hasInit() && !isInitConstant(varDecl))
+ return true;
+
+ maVarDeclMap[varDecl].mnFirstDepth = mnCurrentDepth;
+ maVarDeclMap[varDecl].mnFirstLoopDepth = mnCurrentLoopDepth;
+ maVarDeclMap[varDecl].maDeclBlockPath = maCurrentBlockPath;
+
+ return true;
+}
+
+bool ReduceVarScope::isInitConstant(const VarDecl* varDecl)
+{
+ // check for string or scalar literals
+ const Expr* initExpr = varDecl->getInit();
+ if (auto e = dyn_cast<ExprWithCleanups>(initExpr))
+ initExpr = e->getSubExpr();
+ if (isa<clang::StringLiteral>(initExpr))
+ return true;
+ if (auto constructExpr = dyn_cast<CXXConstructExpr>(initExpr))
+ {
+ if (constructExpr->getNumArgs() == 0)
+ {
+ return true; // i.e., empty string
+ }
+ else
+ {
+ auto stringLit2 = dyn_cast<clang::StringLiteral>(constructExpr->getArg(0));
+ if (stringLit2)
+ return true;
+ }
+ }
+
+ auto const init = varDecl->getInit();
+ if (init->isValueDependent())
+ return false;
+ return init->isConstantInitializer(compiler.getASTContext(), false /*ForRef*/);
+}
+
+bool ReduceVarScope::isTypeOK(QualType varType)
+{
+ // TODO improve this - requires more analysis because it's really easy to
+ // take a pointer to an array
+ if (varType->isArrayType())
+ return false;
+
+ if (varType.isCXX11PODType(compiler.getASTContext()))
+ return true;
+ if (!varType->isRecordType())
+ return false;
+ auto recordDecl = dyn_cast_or_null<CXXRecordDecl>(varType->getAs<RecordType>()->getDecl());
+ if (recordDecl && recordDecl->hasTrivialDestructor())
+ return true;
+ auto const tc = loplugin::TypeCheck(varType);
+ // Safe types with destructors that don't do anything interesting
+ if (tc.Class("OString").Namespace("rtl").GlobalNamespace()
+ || tc.Class("OUString").Namespace("rtl").GlobalNamespace()
+ || tc.Class("OStringBuffer").Namespace("rtl").GlobalNamespace()
+ || tc.Class("OUStringBuffer").Namespace("rtl").GlobalNamespace()
+ || tc.Class("Color").GlobalNamespace() || tc.Class("Pair").GlobalNamespace()
+ || tc.Class("Point").GlobalNamespace() || tc.Class("Size").GlobalNamespace()
+ || tc.Class("Range").GlobalNamespace() || tc.Class("Selection").GlobalNamespace()
+ || tc.Class("Rectangle").Namespace("tools").GlobalNamespace())
+ return true;
+ return false;
+}
+
+bool ReduceVarScope::VisitDeclRefExpr(const DeclRefExpr* declRefExpr)
+{
+ if (ignoreLocation(declRefExpr))
+ return true;
+ const Decl* decl = declRefExpr->getDecl();
+ if (!isa<VarDecl>(decl) || isa<ParmVarDecl>(decl))
+ return true;
+ const VarDecl* varDecl = dyn_cast<VarDecl>(decl)->getCanonicalDecl();
+ // ignore stuff in header files (which should really not be there, but anyhow)
+ if (!compiler.getSourceManager().isInMainFile(varDecl->getLocation()))
+ return true;
+
+ auto varIt = maVarDeclMap.find(varDecl);
+ if (varIt == maVarDeclMap.end())
+ return true;
+
+ auto& depthInfo = varIt->second;
+
+ // merge block paths to get common ancestor path
+ if (depthInfo.maCommonBlockPath.empty())
+ depthInfo.maCommonBlockPath = maCurrentBlockPath;
+ else
+ {
+ auto len = std::min(depthInfo.maCommonBlockPath.size(), maCurrentBlockPath.size());
+ unsigned int i = 0;
+ while (i < len && depthInfo.maCommonBlockPath[i] == maCurrentBlockPath[i])
+ ++i;
+ depthInfo.maCommonBlockPath.resize(i);
+ if (depthInfo.maCommonBlockPath == depthInfo.maDeclBlockPath)
+ {
+ maVarDeclMap.erase(varIt);
+ maVarUseSourceRangeMap.erase(varDecl);
+ return true;
+ }
+ }
+
+ // seen in a loop below initial decl
+ if (mnCurrentLoopDepth > depthInfo.mnFirstLoopDepth)
+ {
+ // TODO, we could additionally check if we are reading or writing to the var inside a loop
+ // We only need to exclude vars that are written to, or passed taken-addr-of, or have non-const method called,
+ // or passed as arg to non-const-ref parameter.
+ maVarDeclMap.erase(varIt);
+ maVarUseSourceRangeMap.erase(varDecl);
+ return true;
+ }
+
+ auto it = maVarUseSourceRangeMap.find(varDecl);
+ if (it == maVarUseSourceRangeMap.end())
+ it = maVarUseSourceRangeMap.emplace(varDecl, std::vector<SourceRange>()).first;
+ it->second.push_back(declRefExpr->getSourceRange());
+
+ return true;
+}
+
+bool ReduceVarScope::VisitLambdaExpr(const LambdaExpr* lambdaExpr)
+{
+ if (ignoreLocation(lambdaExpr))
+ return true;
+ for (auto captureIt = lambdaExpr->capture_begin(); captureIt != lambdaExpr->capture_end();
+ ++captureIt)
+ {
+ const LambdaCapture& capture = *captureIt;
+ if (capture.capturesVariable())
+ {
+ auto varDecl = capture.getCapturedVar();
+ maVarDeclMap.erase(varDecl);
+ maVarUseSourceRangeMap.erase(varDecl);
+ }
+ }
+ return true;
+}
+
+loplugin::Plugin::Registration<ReduceVarScope> reducevarscope("reducevarscope", false);
+}
+
+/* vim:set shiftwidth=4 softtabstop=4 expandtab: */