2015-12-30 18:24:40 +08:00
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//===--- UnnecessaryCopyInitialization.cpp - clang-tidy--------------------===//
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//
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// The LLVM Compiler Infrastructure
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//
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// This file is distributed under the University of Illinois Open Source
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// License. See LICENSE.TXT for details.
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//
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//===----------------------------------------------------------------------===//
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#include "UnnecessaryCopyInitialization.h"
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2016-03-06 05:17:58 +08:00
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#include "../utils/DeclRefExprUtils.h"
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#include "../utils/FixItHintUtils.h"
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#include "../utils/Matchers.h"
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#include "../utils/OptionsUtils.h"
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2015-12-30 18:24:40 +08:00
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namespace clang {
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namespace tidy {
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namespace performance {
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namespace {
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void recordFixes(const VarDecl &Var, ASTContext &Context,
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DiagnosticBuilder &Diagnostic) {
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Diagnostic << utils::fixit::changeVarDeclToReference(Var, Context);
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if (!Var.getType().isLocalConstQualified())
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Diagnostic << utils::fixit::changeVarDeclToConst(Var);
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}
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} // namespace
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2015-12-30 18:24:40 +08:00
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using namespace ::clang::ast_matchers;
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using utils::decl_ref_expr::isOnlyUsedAsConst;
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UnnecessaryCopyInitialization::UnnecessaryCopyInitialization(
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StringRef Name, ClangTidyContext *Context)
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: ClangTidyCheck(Name, Context),
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AllowedTypes(
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utils::options::parseStringList(Options.get("AllowedTypes", ""))) {}
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void UnnecessaryCopyInitialization::registerMatchers(MatchFinder *Finder) {
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auto ConstReference = referenceType(pointee(qualType(isConstQualified())));
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auto ConstOrConstReference =
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allOf(anyOf(ConstReference, isConstQualified()),
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unless(allOf(pointerType(), unless(pointerType(pointee(
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qualType(isConstQualified())))))));
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// Match method call expressions where the `this` argument is only used as
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// const, this will be checked in `check()` part. This returned const
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// reference is highly likely to outlive the local const reference of the
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// variable being declared. The assumption is that the const reference being
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// returned either points to a global static variable or to a member of the
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// called object.
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auto ConstRefReturningMethodCall =
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cxxMemberCallExpr(callee(cxxMethodDecl(returns(ConstReference))),
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on(declRefExpr(to(varDecl().bind("objectArg")))));
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auto ConstRefReturningFunctionCall =
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callExpr(callee(functionDecl(returns(ConstReference))),
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unless(callee(cxxMethodDecl())));
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auto localVarCopiedFrom = [this](const internal::Matcher<Expr> &CopyCtorArg) {
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return compoundStmt(
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forEachDescendant(
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declStmt(
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has(varDecl(hasLocalStorage(),
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hasType(qualType(
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allOf(hasCanonicalType(
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matchers::isExpensiveToCopy()),
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unless(hasDeclaration(namedDecl(
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matchers::matchesAnyListedName(
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AllowedTypes))))))),
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unless(isImplicit()),
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hasInitializer(
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cxxConstructExpr(
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hasDeclaration(cxxConstructorDecl(
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isCopyConstructor())),
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hasArgument(0, CopyCtorArg))
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.bind("ctorCall")))
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.bind("newVarDecl")))
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.bind("declStmt")))
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.bind("blockStmt");
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};
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Finder->addMatcher(localVarCopiedFrom(anyOf(ConstRefReturningFunctionCall,
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ConstRefReturningMethodCall)),
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this);
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Finder->addMatcher(localVarCopiedFrom(declRefExpr(
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to(varDecl(hasLocalStorage()).bind("oldVarDecl")))),
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this);
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}
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void UnnecessaryCopyInitialization::check(
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const MatchFinder::MatchResult &Result) {
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const auto *NewVar = Result.Nodes.getNodeAs<VarDecl>("newVarDecl");
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const auto *OldVar = Result.Nodes.getNodeAs<VarDecl>("oldVarDecl");
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const auto *ObjectArg = Result.Nodes.getNodeAs<VarDecl>("objectArg");
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const auto *BlockStmt = Result.Nodes.getNodeAs<Stmt>("blockStmt");
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const auto *CtorCall = Result.Nodes.getNodeAs<CXXConstructExpr>("ctorCall");
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// Do not propose fixes if the DeclStmt has multiple VarDecls or in macros
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// since we cannot place them correctly.
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bool IssueFix =
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Result.Nodes.getNodeAs<DeclStmt>("declStmt")->isSingleDecl() &&
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!NewVar->getLocation().isMacroID();
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// A constructor that looks like T(const T& t, bool arg = false) counts as a
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// copy only when it is called with default arguments for the arguments after
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// the first.
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for (unsigned int i = 1; i < CtorCall->getNumArgs(); ++i)
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if (!CtorCall->getArg(i)->isDefaultArgument())
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return;
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if (OldVar == nullptr) {
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handleCopyFromMethodReturn(*NewVar, *BlockStmt, IssueFix, ObjectArg,
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*Result.Context);
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} else {
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handleCopyFromLocalVar(*NewVar, *OldVar, *BlockStmt, IssueFix,
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*Result.Context);
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}
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}
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void UnnecessaryCopyInitialization::handleCopyFromMethodReturn(
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const VarDecl &Var, const Stmt &BlockStmt, bool IssueFix,
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const VarDecl *ObjectArg, ASTContext &Context) {
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bool IsConstQualified = Var.getType().isConstQualified();
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if (!IsConstQualified && !isOnlyUsedAsConst(Var, BlockStmt, Context))
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return;
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if (ObjectArg != nullptr &&
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!isOnlyUsedAsConst(*ObjectArg, BlockStmt, Context))
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return;
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auto Diagnostic =
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diag(Var.getLocation(),
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IsConstQualified ? "the const qualified variable %0 is "
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"copy-constructed from a const reference; "
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"consider making it a const reference"
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: "the variable %0 is copy-constructed from a "
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"const reference but is only used as const "
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"reference; consider making it a const reference")
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<< &Var;
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if (IssueFix)
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recordFixes(Var, Context, Diagnostic);
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}
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void UnnecessaryCopyInitialization::handleCopyFromLocalVar(
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const VarDecl &NewVar, const VarDecl &OldVar, const Stmt &BlockStmt,
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bool IssueFix, ASTContext &Context) {
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if (!isOnlyUsedAsConst(NewVar, BlockStmt, Context) ||
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!isOnlyUsedAsConst(OldVar, BlockStmt, Context))
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return;
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auto Diagnostic = diag(NewVar.getLocation(),
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"local copy %0 of the variable %1 is never modified; "
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"consider avoiding the copy")
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<< &NewVar << &OldVar;
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if (IssueFix)
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recordFixes(NewVar, Context, Diagnostic);
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}
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2018-10-12 21:05:21 +08:00
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void UnnecessaryCopyInitialization::storeOptions(
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ClangTidyOptions::OptionMap &Opts) {
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Options.store(Opts, "AllowedTypes",
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utils::options::serializeStringList(AllowedTypes));
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}
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2015-12-30 18:24:40 +08:00
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} // namespace performance
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} // namespace tidy
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} // namespace clang
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