| //===--- BranchCloneCheck.cpp - clang-tidy --------------------------------===// |
| // |
| // The LLVM Compiler Infrastructure |
| // |
| // This file is distributed under the University of Illinois Open Source |
| // License. See LICENSE.TXT for details. |
| // |
| //===----------------------------------------------------------------------===// |
| |
| #include "BranchCloneCheck.h" |
| #include "clang/AST/ASTContext.h" |
| #include "clang/ASTMatchers/ASTMatchFinder.h" |
| #include "clang/Analysis/CloneDetection.h" |
| #include "clang/Lex/Lexer.h" |
| #include "llvm/Support/Casting.h" |
| |
| using namespace clang; |
| using namespace clang::ast_matchers; |
| |
| /// Returns true when the statements are Type I clones of each other. |
| static bool areStatementsIdentical(const Stmt *LHS, const Stmt *RHS, |
| const ASTContext &Context) { |
| llvm::FoldingSetNodeID DataLHS, DataRHS; |
| LHS->Profile(DataLHS, Context, false); |
| RHS->Profile(DataRHS, Context, false); |
| return (DataLHS == DataRHS); |
| } |
| |
| namespace { |
| /// A branch in a switch may consist of several statements; while a branch in |
| /// an if/else if/else chain is one statement (which may be a CompoundStmt). |
| using SwitchBranch = llvm::SmallVector<const Stmt *, 2>; |
| } // anonymous namespace |
| |
| /// Determines if the bodies of two branches in a switch statements are Type I |
| /// clones of each other. This function only examines the body of the branch |
| /// and ignores the `case X:` or `default:` at the start of the branch. |
| static bool areSwitchBranchesIdentical(const SwitchBranch LHS, |
| const SwitchBranch RHS, |
| const ASTContext &Context) { |
| if (LHS.size() != RHS.size()) |
| return false; |
| |
| for (size_t I = 0, Size = LHS.size(); I < Size; I++) { |
| // NOTE: We strip goto labels and annotations in addition to stripping |
| // the `case X:` or `default:` labels, but it is very unlikely that this |
| // would casue false positives in real-world code. |
| if (!areStatementsIdentical(LHS[I]->stripLabelLikeStatements(), |
| RHS[I]->stripLabelLikeStatements(), Context)) { |
| return false; |
| } |
| } |
| |
| return true; |
| } |
| |
| namespace clang { |
| namespace tidy { |
| namespace bugprone { |
| |
| void BranchCloneCheck::registerMatchers(MatchFinder *Finder) { |
| Finder->addMatcher( |
| ifStmt(unless(allOf(isConstexpr(), isInTemplateInstantiation())), |
| stmt().bind("if"), |
| hasParent(stmt(unless(ifStmt(hasElse(equalsBoundNode("if")))))), |
| hasElse(stmt().bind("else"))), |
| this); |
| Finder->addMatcher(switchStmt().bind("switch"), this); |
| Finder->addMatcher(conditionalOperator().bind("condOp"), this); |
| } |
| |
| void BranchCloneCheck::check(const MatchFinder::MatchResult &Result) { |
| const ASTContext &Context = *Result.Context; |
| |
| if (const auto *IS = Result.Nodes.getNodeAs<IfStmt>("if")) { |
| const Stmt *Then = IS->getThen(); |
| assert(Then && "An IfStmt must have a `then` branch!"); |
| |
| const Stmt *Else = Result.Nodes.getNodeAs<Stmt>("else"); |
| assert(Else && "We only look for `if` statements with an `else` branch!"); |
| |
| if (!isa<IfStmt>(Else)) { |
| // Just a simple if with no `else if` branch. |
| if (areStatementsIdentical(Then->IgnoreContainers(), |
| Else->IgnoreContainers(), Context)) { |
| diag(IS->getBeginLoc(), "if with identical then and else branches"); |
| diag(IS->getElseLoc(), "else branch starts here", DiagnosticIDs::Note); |
| } |
| return; |
| } |
| |
| // This is the complicated case when we start an if/else if/else chain. |
| // To find all the duplicates, we collect all the branches into a vector. |
| llvm::SmallVector<const Stmt *, 4> Branches; |
| const IfStmt *Cur = IS; |
| while (true) { |
| // Store the `then` branch. |
| Branches.push_back(Cur->getThen()); |
| |
| Else = Cur->getElse(); |
| // The chain ends if there is no `else` branch. |
| if (!Else) |
| break; |
| |
| // Check if there is another `else if`... |
| Cur = dyn_cast<IfStmt>(Else); |
| if (!Cur) { |
| // ...this is just a plain `else` branch at the end of the chain. |
| Branches.push_back(Else); |
| break; |
| } |
| } |
| |
| size_t N = Branches.size(); |
| llvm::BitVector KnownAsClone(N); |
| |
| for (size_t I = 0; I + 1 < N; I++) { |
| // We have already seen Branches[i] as a clone of an earlier branch. |
| if (KnownAsClone[I]) |
| continue; |
| |
| int NumCopies = 1; |
| |
| for (size_t J = I + 1; J < N; J++) { |
| if (KnownAsClone[J] || |
| !areStatementsIdentical(Branches[I]->IgnoreContainers(), |
| Branches[J]->IgnoreContainers(), Context)) |
| continue; |
| |
| NumCopies++; |
| KnownAsClone[J] = true; |
| |
| if (NumCopies == 2) { |
| // We report the first occurrence only when we find the second one. |
| diag(Branches[I]->getBeginLoc(), |
| "repeated branch in conditional chain"); |
| SourceLocation End = |
| Lexer::getLocForEndOfToken(Branches[I]->getEndLoc(), 0, |
| *Result.SourceManager, getLangOpts()); |
| if (End.isValid()) { |
| diag(End, "end of the original", DiagnosticIDs::Note); |
| } |
| } |
| |
| diag(Branches[J]->getBeginLoc(), "clone %0 starts here", |
| DiagnosticIDs::Note) |
| << (NumCopies - 1); |
| } |
| } |
| return; |
| } |
| |
| if (const auto *CO = Result.Nodes.getNodeAs<ConditionalOperator>("condOp")) { |
| // We do not try to detect chains of ?: operators. |
| if (areStatementsIdentical(CO->getTrueExpr(), CO->getFalseExpr(), Context)) |
| diag(CO->getQuestionLoc(), |
| "conditional operator with identical true and false expressions"); |
| |
| return; |
| } |
| |
| if (const auto *SS = Result.Nodes.getNodeAs<SwitchStmt>("switch")) { |
| const CompoundStmt *Body = dyn_cast_or_null<CompoundStmt>(SS->getBody()); |
| |
| // Code like |
| // switch (x) case 0: case 1: foobar(); |
| // is legal and calls foobar() if and only if x is either 0 or 1; |
| // but we do not try to distinguish branches in such code. |
| if (!Body) |
| return; |
| |
| // We will first collect the branches of the switch statements. For the |
| // sake of simplicity we say that branches are delimited by the SwitchCase |
| // (`case:` or `default:`) children of Body; that is, we ignore `case:` or |
| // `default:` labels embedded inside other statements and we do not follow |
| // the effects of `break` and other manipulation of the control-flow. |
| llvm::SmallVector<SwitchBranch, 4> Branches; |
| for (const Stmt *S : Body->body()) { |
| // If this is a `case` or `default`, we start a new, empty branch. |
| if (isa<SwitchCase>(S)) |
| Branches.emplace_back(); |
| |
| // There may be code before the first branch (which can be dead code |
| // and can be code reached either through goto or through case labels |
| // that are embedded inside e.g. inner compound statements); we do not |
| // store those statements in branches. |
| if (!Branches.empty()) |
| Branches.back().push_back(S); |
| } |
| |
| auto End = Branches.end(); |
| auto BeginCurrent = Branches.begin(); |
| while (BeginCurrent < End) { |
| auto EndCurrent = BeginCurrent + 1; |
| while (EndCurrent < End && |
| areSwitchBranchesIdentical(*BeginCurrent, *EndCurrent, Context)) { |
| ++EndCurrent; |
| } |
| // At this point the iterator range {BeginCurrent, EndCurrent} contains a |
| // complete family of consecutive identical branches. |
| if (EndCurrent > BeginCurrent + 1) { |
| diag(BeginCurrent->front()->getBeginLoc(), |
| "switch has %0 consecutive identical branches") |
| << static_cast<int>(std::distance(BeginCurrent, EndCurrent)); |
| |
| SourceLocation EndLoc = (EndCurrent - 1)->back()->getEndLoc(); |
| // If the case statement is generated from a macro, it's SourceLocation |
| // may be invalid, resulting in an assertion failure down the line. |
| // While not optimal, try the begin location in this case, it's still |
| // better then nothing. |
| if (EndLoc.isInvalid()) |
| EndLoc = (EndCurrent - 1)->back()->getBeginLoc(); |
| |
| if (EndLoc.isMacroID()) |
| EndLoc = Context.getSourceManager().getExpansionLoc(EndLoc); |
| EndLoc = Lexer::getLocForEndOfToken(EndLoc, 0, *Result.SourceManager, |
| getLangOpts()); |
| |
| if (EndLoc.isValid()) { |
| diag(EndLoc, "last of these clones ends here", DiagnosticIDs::Note); |
| } |
| } |
| BeginCurrent = EndCurrent; |
| } |
| return; |
| } |
| |
| llvm_unreachable("No if statement and no switch statement."); |
| } |
| |
| } // namespace bugprone |
| } // namespace tidy |
| } // namespace clang |