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Diffstat (limited to 'compilerplugins/clang/redundantcast.cxx')
| -rw-r--r-- | compilerplugins/clang/redundantcast.cxx | 969 |
1 files changed, 969 insertions, 0 deletions
diff --git a/compilerplugins/clang/redundantcast.cxx b/compilerplugins/clang/redundantcast.cxx new file mode 100644 index 000000000..87c4d1445 --- /dev/null +++ b/compilerplugins/clang/redundantcast.cxx @@ -0,0 +1,969 @@ +/* -*- 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/. + */ + +// Warn about certain redundant casts: +// +// * A reinterpret_cast<T*>(...) whose result is then implicitly cast to a void +// pointer +// +// * A static_cast<T*>(e) where e is of void pointer type and whose result is +// then implicitly cast to a void pointer +// +// * Various const_casts that are either not needed (like casting away constness +// in a delete expression) or are implicitly cast back afterwards +// +// C-style casts are ignored because it makes this plugin simpler, and they +// should eventually be eliminated via loplugin:cstylecast and/or +// -Wold-style-cast. That implies that this plugin is only relevant for C++ +// code. + +#include "clang/Sema/Sema.h" + +#include "check.hxx" +#include "compat.hxx" +#include "plugin.hxx" +#include <iostream> + +namespace { + +bool isVoidPointer(QualType type) { + return type->isPointerType() + && type->getAs<clang::PointerType>()->getPointeeType()->isVoidType(); +} + +bool isRedundantConstCast(CXXConstCastExpr const * expr) { + auto const sub = compat::getSubExprAsWritten(expr); + return + (expr->getType().getCanonicalType() + == sub->getType().getCanonicalType()) + && (expr->getValueKind() != VK_XValue + || sub->getValueKind() == VK_XValue); +} + +bool canConstCastFromTo(Expr const * from, Expr const * to) { + auto const k1 = from->getValueKind(); + auto const k2 = to->getValueKind(); + return (k2 == VK_LValue && k1 == VK_LValue) + || (k2 == VK_XValue + && (k1 != compat::VK_PRValue || from->getType()->isRecordType())); +} + +char const * printExprValueKind(ExprValueKind k) { + switch (k) { + case compat::VK_PRValue: + return "prvalue"; + case VK_LValue: + return "lvalue"; + case VK_XValue: + return "xvalue"; + }; + llvm_unreachable("unknown ExprValueKind"); +} + +enum class AlgebraicType { None, Integer, FloatingPoint }; + +AlgebraicType algebraicType(clang::Type const & type) { + if (type.isIntegralOrEnumerationType()) { + return AlgebraicType::Integer; + } else if (type.isRealFloatingType()) { + return AlgebraicType::FloatingPoint; + } else { + return AlgebraicType::None; + } +} + +// Do not look through FunctionToPointerDecay, but through e.g. NullToPointer: +Expr const * stopAtFunctionPointerDecay(ExplicitCastExpr const * expr) { + auto const e1 = expr->getSubExpr(); + if (auto const e2 = dyn_cast<ImplicitCastExpr>(e1)) { + if (e2->getCastKind() != CK_FunctionToPointerDecay) { + return e2->getSubExpr(); + } + } + return e1; +} + +class RedundantCast: + public loplugin::FilteringRewritePlugin<RedundantCast> +{ +public: + explicit RedundantCast(loplugin::InstantiationData const & data): + FilteringRewritePlugin(data) + {} + + virtual void run() override { + if (compiler.getLangOpts().CPlusPlus) { + TraverseDecl(compiler.getASTContext().getTranslationUnitDecl()); + } + } + + bool TraverseInitListExpr(InitListExpr * expr, DataRecursionQueue * queue = nullptr) { + return WalkUpFromInitListExpr(expr) + && TraverseSynOrSemInitListExpr( + expr->isSemanticForm() ? expr : expr->getSemanticForm(), queue); + } + + bool TraverseReturnStmt(ReturnStmt * stmt) { + auto const saved = returnExpr_; + returnExpr_ = stmt->getRetValue(); + auto const ret = FilteringRewritePlugin::TraverseReturnStmt(stmt); + returnExpr_ = saved; + return ret; + } + + bool VisitImplicitCastExpr(ImplicitCastExpr const * expr); + + bool VisitCXXStaticCastExpr(CXXStaticCastExpr const * expr); + + bool VisitCXXReinterpretCastExpr(CXXReinterpretCastExpr const * expr); + + bool VisitCXXConstCastExpr(CXXConstCastExpr const * expr); + + bool VisitCXXFunctionalCastExpr(CXXFunctionalCastExpr const * expr); + + bool VisitCXXDynamicCastExpr(CXXDynamicCastExpr const * expr); + + bool VisitCallExpr(CallExpr const * expr); + + bool VisitCXXDeleteExpr(CXXDeleteExpr const * expr); + + bool VisitCStyleCastExpr(CStyleCastExpr const * expr); + + bool VisitBinaryOperator(BinaryOperator const * expr) { + auto const op = expr->getOpcode(); + if (op == BO_Sub || expr->isRelationalOp() || expr->isEqualityOp()) { + return visitBinOp(expr); + } + if (op == BO_Assign) { + if (ignoreLocation(expr)) { + return true; + } + visitAssign(expr->getLHS()->getType(), expr->getRHS()); + return true; + } + return true; + } + + bool VisitVarDecl(VarDecl const * varDecl); + +private: + bool visitBinOp(BinaryOperator const * expr); + void visitAssign(QualType lhs, Expr const * rhs); + bool isOverloadedFunction(FunctionDecl const * decl); + + bool isInIgnoredMacroBody(Expr const * expr) { + auto const loc = expr->getBeginLoc(); + return compiler.getSourceManager().isMacroBodyExpansion(loc) + && ignoreLocation(compiler.getSourceManager().getSpellingLoc(loc)); + } + + Expr const * returnExpr_ = nullptr; +}; + +bool RedundantCast::VisitImplicitCastExpr(const ImplicitCastExpr * expr) { + if (ignoreLocation(expr)) { + return true; + } + switch (expr->getCastKind()) { + case CK_NoOp: + if (expr->getType()->isPointerType() + || expr->getType()->isObjectType()) + { + auto e = dyn_cast<CXXConstCastExpr>( + expr->getSubExpr()->IgnoreParenImpCasts()); + if (e != nullptr && !isRedundantConstCast(e)) { + auto t1 = e->getSubExpr()->getType().getCanonicalType(); + auto t3 = expr->getType().getCanonicalType(); + bool ObjCLifetimeConversion; + if (t1.getTypePtr() == t3.getTypePtr() + || (compiler.getSema().IsQualificationConversion( + t1, t3, false, ObjCLifetimeConversion) + && (e->getType().getCanonicalType().getTypePtr() + != t3.getTypePtr()))) + { + report( + DiagnosticsEngine::Warning, + ("redundant const_cast from %0 to %1, result is" + " implicitly cast to %2"), + e->getExprLoc()) + << e->getSubExprAsWritten()->getType() << e->getType() + << expr->getType() << expr->getSourceRange(); + } + } + } + break; + case CK_BitCast: + if (isVoidPointer(expr->getType()) + && expr->getSubExpr()->getType()->isPointerType()) + { + Expr const * e = expr->getSubExpr()->IgnoreParenImpCasts(); + while (isa<CXXConstCastExpr>(e)) { + auto cc = dyn_cast<CXXConstCastExpr>(e); + if (expr->getType()->getAs<clang::PointerType>() + ->getPointeeType().isAtLeastAsQualifiedAs( + cc->getSubExpr()->getType() + ->getAs<clang::PointerType>()->getPointeeType())) + { + report( + DiagnosticsEngine::Warning, + ("redundant const_cast from %0 to %1, result is" + " ultimately implicitly cast to %2"), + cc->getExprLoc()) + << cc->getSubExprAsWritten()->getType() << cc->getType() + << expr->getType() << expr->getSourceRange(); + } + e = cc->getSubExpr()->IgnoreParenImpCasts(); + } + if (isa<CXXReinterpretCastExpr>(e)) { + report( + DiagnosticsEngine::Warning, + ("redundant reinterpret_cast, result is implicitly cast to" + " void pointer"), + e->getExprLoc()) + << e->getSourceRange(); + } else if (isa<CXXStaticCastExpr>(e) + && isVoidPointer( + dyn_cast<CXXStaticCastExpr>(e)->getSubExpr() + ->IgnoreParenImpCasts()->getType()) + && !compiler.getSourceManager().isMacroBodyExpansion( + e->getBeginLoc())) + { + report( + DiagnosticsEngine::Warning, + ("redundant static_cast from void pointer, result is" + " implicitly cast to void pointer"), + e->getExprLoc()) + << e->getSourceRange(); + } + } + break; + case CK_DerivedToBase: + case CK_UncheckedDerivedToBase: + if (expr->getType()->isPointerType()) { + Expr const * e = expr->getSubExpr()->IgnoreParenImpCasts(); + while (isa<CXXConstCastExpr>(e)) { + auto cc = dyn_cast<CXXConstCastExpr>(e); + if (expr->getType()->getAs<clang::PointerType>() + ->getPointeeType().isAtLeastAsQualifiedAs( + cc->getSubExpr()->getType() + ->getAs<clang::PointerType>()->getPointeeType())) + { + report( + DiagnosticsEngine::Warning, + ("redundant const_cast from %0 to %1, result is" + " ultimately implicitly cast to %2"), + cc->getExprLoc()) + << cc->getSubExprAsWritten()->getType() << cc->getType() + << expr->getType() << expr->getSourceRange(); + } + e = cc->getSubExpr()->IgnoreParenImpCasts(); + } + } else if (expr->getType()->isReferenceType()) { + Expr const * e = expr->getSubExpr()->IgnoreParenImpCasts(); + while (isa<CXXConstCastExpr>(e)) { + auto cc = dyn_cast<CXXConstCastExpr>(e); + if (expr->getType()->getAs<ReferenceType>()->getPointeeType() + .isAtLeastAsQualifiedAs( + cc->getSubExpr()->getType() + ->getAs<ReferenceType>()->getPointeeType())) + { + report( + DiagnosticsEngine::Warning, + ("redundant const_cast from %0 to %1, result is" + " ultimately implicitly cast to %2"), + cc->getExprLoc()) + << cc->getSubExprAsWritten()->getType() << cc->getType() + << expr->getType() << expr->getSourceRange(); + } + e = cc->getSubExpr()->IgnoreParenImpCasts(); + } + } + break; + case CK_FloatingToIntegral: + case CK_IntegralToFloating: + if (auto e = dyn_cast<ExplicitCastExpr>(expr->getSubExpr()->IgnoreParenImpCasts())) { + if ((isa<CXXStaticCastExpr>(e) || isa<CXXFunctionalCastExpr>(e)) + && (algebraicType(*e->getSubExprAsWritten()->getType()) + == algebraicType(*expr->getType()))) + { + report( + DiagnosticsEngine::Warning, + ("suspicious %select{static_cast|functional cast}0 from %1 to %2, result is" + " implicitly cast to %3"), + e->getExprLoc()) + << isa<CXXFunctionalCastExpr>(e) << e->getSubExprAsWritten()->getType() + << e->getTypeAsWritten() << expr->getType() << expr->getSourceRange(); + } + } + break; + default: + break; + } + return true; +} + +bool RedundantCast::VisitCStyleCastExpr(CStyleCastExpr const * expr) { + if (ignoreLocation(expr)) { + return true; + } + if (isInUnoIncludeFile(compiler.getSourceManager().getSpellingLoc(expr->getBeginLoc()))) { + return true; + } + auto t1 = compat::getSubExprAsWritten(expr)->getType(); + auto t2 = expr->getTypeAsWritten(); + if (auto templateType = dyn_cast<SubstTemplateTypeParmType>(t1)) { + t1 = templateType->desugar(); + } + if (t1 != t2) { + return true; + } + if (!t1->isBuiltinType() && !loplugin::TypeCheck(t1).Enum() && !loplugin::TypeCheck(t1).Typedef()) { + return true; + } + if (!loplugin::isOkToRemoveArithmeticCast(compiler.getASTContext(), t1, t2, expr->getSubExpr())) + { + return true; + } + // Ignore FD_ISSET expanding to "...(SOCKET)(fd)..." in some Microsoft + // winsock2.h (TODO: improve heuristic of determining that the whole + // expr is part of a single macro body expansion): + auto l1 = expr->getBeginLoc(); + while (compiler.getSourceManager().isMacroArgExpansion(l1)) { + l1 = compiler.getSourceManager().getImmediateMacroCallerLoc(l1); + } + auto l2 = expr->getExprLoc(); + while (compiler.getSourceManager().isMacroArgExpansion(l2)) { + l2 = compiler.getSourceManager().getImmediateMacroCallerLoc(l2); + } + auto l3 = expr->getEndLoc(); + while (compiler.getSourceManager().isMacroArgExpansion(l3)) { + l3 = compiler.getSourceManager().getImmediateMacroCallerLoc(l3); + } + if (compiler.getSourceManager().isMacroBodyExpansion(l1) + && compiler.getSourceManager().isMacroBodyExpansion(l2) + && compiler.getSourceManager().isMacroBodyExpansion(l3) + && ignoreLocation(compiler.getSourceManager().getSpellingLoc(l2))) + { + return true; + } + report( + DiagnosticsEngine::Warning, + "redundant cstyle cast from %0 to %1", expr->getExprLoc()) + << t1 << t2 << expr->getSourceRange(); + return true; +} + +bool RedundantCast::VisitVarDecl(VarDecl const * varDecl) { + if (ignoreLocation(varDecl)) { + return true; + } + if (!varDecl->getInit()) + return true; + visitAssign(varDecl->getType(), varDecl->getInit()); + return true; +} + +void RedundantCast::visitAssign(QualType t1, Expr const * rhs) +{ + auto staticCastExpr = dyn_cast<CXXStaticCastExpr>(rhs->IgnoreImplicit()); + if (!staticCastExpr) + return; + + auto const t2 = staticCastExpr->getSubExpr()->IgnoreImplicit()->getType(); + + // if there is more than one copy of the LHS, this cast is resolving ambiguity + bool foundOne = false; + if (t1->isRecordType()) + { + foundOne = loplugin::derivedFromCount(t2, t1) == 1; + } + else + { + auto pointee1 = t1->getPointeeCXXRecordDecl(); + auto pointee2 = t2->getPointeeCXXRecordDecl(); + if (pointee1 && pointee2) + foundOne = loplugin::derivedFromCount(pointee2, pointee1) == 1; + } + + if (foundOne) + { + report( + DiagnosticsEngine::Warning, "redundant static_cast from %0 to %1", + staticCastExpr->getExprLoc()) + << t2 << t1 << staticCastExpr->getSourceRange(); + } +} + +bool RedundantCast::VisitCXXStaticCastExpr(CXXStaticCastExpr const * expr) { + if (ignoreLocation(expr)) { + return true; + } + auto const t2 = expr->getTypeAsWritten(); + bool const fnptr = t2->isFunctionPointerType() || t2->isMemberFunctionPointerType(); + auto const sub = fnptr ? stopAtFunctionPointerDecay(expr) : compat::getSubExprAsWritten(expr); + auto const t1 = sub->getType(); + auto const nonClassObjectType = t2->isObjectType() + && !(t2->isRecordType() || t2->isArrayType()); + if (nonClassObjectType && t2.hasLocalQualifiers()) { + report( + DiagnosticsEngine::Warning, + ("in static_cast from %0 %1 to %2 %3, remove redundant top-level" + " %select{const qualifier|volatile qualifier|const volatile" + " qualifiers}4"), + expr->getExprLoc()) + << t1 << printExprValueKind(sub->getValueKind()) + << t2 << printExprValueKind(expr->getValueKind()) + << ((t2.isLocalConstQualified() ? 1 : 0) + + (t2.isLocalVolatileQualified() ? 2 : 0) - 1) + << expr->getSourceRange(); + return true; + } + if (auto const impl = dyn_cast<ImplicitCastExpr>(expr->getSubExpr())) { + if (impl->getCastKind() == CK_ArrayToPointerDecay && impl->getType() == t2) + //TODO: instead of exact QualType match, allow some variation? + { + auto const fn = handler.getMainFileName(); + if (!(loplugin::isSamePathname( + fn, SRCDIR "/sal/qa/rtl/strings/test_ostring_concat.cxx") + || loplugin::isSamePathname( + fn, SRCDIR "/sal/qa/rtl/strings/test_ostring_stringliterals.cxx") + || loplugin::isSamePathname( + fn, SRCDIR "/sal/qa/rtl/strings/test_oustring_concat.cxx") + || loplugin::isSamePathname( + fn, SRCDIR "/sal/qa/rtl/strings/test_oustring_stringliterals.cxx") + || isInIgnoredMacroBody(expr))) + { + report( + DiagnosticsEngine::Warning, "redundant static_cast from %0 to %1", + expr->getExprLoc()) + << expr->getSubExprAsWritten()->getType() << t2 << expr->getSourceRange(); + } + return true; + } + } + auto const t3 = expr->getType(); + auto const c1 = t1.getCanonicalType(); + auto const c3 = t3.getCanonicalType(); + if (nonClassObjectType || !canConstCastFromTo(sub, expr) + ? c1.getTypePtr() != c3.getTypePtr() : c1 != c3) + { + bool ObjCLifetimeConversion; + if (nonClassObjectType + || (c1.getTypePtr() != c3.getTypePtr() + && !compiler.getSema().IsQualificationConversion( + c1, c3, false, ObjCLifetimeConversion))) + { + return true; + } + report( + DiagnosticsEngine::Warning, + "static_cast from %0 %1 to %2 %3 should be written as const_cast", + expr->getExprLoc()) + << t1 << printExprValueKind(sub->getValueKind()) + << t2 << printExprValueKind(expr->getValueKind()) + << expr->getSourceRange(); + return true; + } + if (!loplugin::isOkToRemoveArithmeticCast(compiler.getASTContext(), t1, t2, expr->getSubExpr())) + { + return true; + } + // Don't warn if the types are 'void *' and at least one involves a typedef + // (and if both involve typedefs, they're different) (this covers cases like + // 'oslModule', or 'CURL *', or casts between 'LPVOID' and 'HANDLE' in + // Windows-only code): + if (loplugin::TypeCheck(t1).Pointer().NonConstVolatile().Void()) { + if (auto const td1 = t1->getAs<TypedefType>()) { + auto const td2 = t2->getAs<TypedefType>(); + if (td2 == nullptr || td2 != td1) { + return true; + } + } else if (auto const td2 = t2->getAs<TypedefType>()) { + auto const td1 = t1->getAs<TypedefType>(); + if (td1 == nullptr || td1 != td2) { + return true; + } + } else { + auto const pt1 = t1->getAs<clang::PointerType>()->getPointeeType(); + auto const pt2 = t2->getAs<clang::PointerType>()->getPointeeType(); + if (auto const ptd1 = pt1->getAs<TypedefType>()) { + auto const ptd2 = pt2->getAs<TypedefType>(); + if (ptd2 == nullptr || ptd2 != ptd1) { + return true; + } + } else if (auto const ptd2 = pt2->getAs<TypedefType>()) { + auto const ptd1 = pt1->getAs<TypedefType>(); + if (ptd1 == nullptr || ptd1 != ptd2) { + return true; + } + } + } + } + auto const k1 = sub->getValueKind(); + auto const k3 = expr->getValueKind(); + if ((k3 == VK_XValue && k1 != VK_XValue) + || (k3 == VK_LValue && k1 == VK_XValue)) + { + return true; + } + // For <http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2021/p2266r1.html> "P2266R1: Simpler + // implicit move" (as implemented with <https://github.com/llvm/llvm-project/commit/ + // bf20631782183cd19e0bb7219e908c2bbb01a75f> "[clang] Implement P2266 Simpler implicit move" + // towards Clang 13), don't warn about a static_cast in a return statement like + // + // return static_cast<int &>(x); + // + // that needs an lvalue but where in a return statement like + // + // return x; + // + // the expression would now be an xvalue: + if (k3 == VK_LValue && k1 == VK_LValue && returnExpr_ != nullptr + && expr == returnExpr_->IgnoreParens()) + { + return true; + } + // Don't warn if a static_cast on a pointer to function or member function is used to + // disambiguate an overloaded function: + if (fnptr) { + auto e = sub->IgnoreParenImpCasts(); + if (auto const e1 = dyn_cast<UnaryOperator>(e)) { + if (e1->getOpcode() == UO_AddrOf) { + e = e1->getSubExpr()->IgnoreParenImpCasts(); + } + } + if (auto const e1 = dyn_cast<DeclRefExpr>(e)) { + if (auto const fdecl = dyn_cast<FunctionDecl>(e1->getDecl())) { + if (isOverloadedFunction(fdecl)) { + return true; + } + } + } + } + // Suppress warnings from static_cast<bool> in C++ definition of assert in + // <https://sourceware.org/git/?p=glibc.git;a=commit; + // h=b5889d25e9bf944a89fdd7bcabf3b6c6f6bb6f7c> "assert: Support types + // without operator== (int) [BZ #21972]": + if (t1->isBooleanType() && t2->isBooleanType()) { + auto loc = expr->getBeginLoc(); + if (compiler.getSourceManager().isMacroBodyExpansion(loc) + && (Lexer::getImmediateMacroName( + loc, compiler.getSourceManager(), compiler.getLangOpts()) + == "assert")) + { + return true; + } + } + report( + DiagnosticsEngine::Warning, + ("static_cast from %0 %1 to %2 %3 is redundant%select{| or should be" + " written as an explicit construction of a temporary}4"), + expr->getExprLoc()) + << t1 << printExprValueKind(k1) << t2 << printExprValueKind(k3) + << (k3 == compat::VK_PRValue && (k1 != compat::VK_PRValue || t1->isRecordType())) + << expr->getSourceRange(); + return true; +} + +bool RedundantCast::VisitCXXReinterpretCastExpr( + CXXReinterpretCastExpr const * expr) +{ + if (ignoreLocation(expr)) { + return true; + } + if (expr->getTypeAsWritten() == expr->getSubExprAsWritten()->getType()) + //TODO: instead of exact QualType match, allow some variation? + { + report( + DiagnosticsEngine::Warning, "redundant reinterpret_cast from %0 to %1", + expr->getExprLoc()) + << expr->getSubExprAsWritten()->getType() << expr->getTypeAsWritten() + << expr->getSourceRange(); + return true; + } + if (auto const sub = dyn_cast<ImplicitCastExpr>(expr->getSubExpr())) { + if (sub->getCastKind() == CK_ArrayToPointerDecay && sub->getType() == expr->getType()) + //TODO: instead of exact QualType match, allow some variation? + { + if (loplugin::TypeCheck(sub->getType()).Pointer().Const().Char()) { + if (auto const lit = dyn_cast<clang::StringLiteral>(expr->getSubExprAsWritten())) { + if (lit->getKind() == clang::StringLiteral::UTF8) { + // Don't warn about + // + // redundant_cast<char const *>(u8"...") + // + // in pre-C++2a code: + return true; + } + } + } + report( + DiagnosticsEngine::Warning, "redundant reinterpret_cast from %0 to %1", + expr->getExprLoc()) + << expr->getSubExprAsWritten()->getType() << expr->getTypeAsWritten() + << expr->getSourceRange(); + return true; + } + } + if (expr->getSubExpr()->getType()->isVoidPointerType()) { + auto t = expr->getType()->getAs<clang::PointerType>(); + if (t == nullptr || !t->getPointeeType()->isObjectType()) { + return true; + } + if (rewriter != nullptr) { + auto loc = expr->getBeginLoc(); + while (compiler.getSourceManager().isMacroArgExpansion(loc)) { + loc = compiler.getSourceManager().getImmediateMacroCallerLoc( + loc); + } + if (compiler.getSourceManager().isMacroBodyExpansion(loc)) { + auto loc2 = expr->getEndLoc(); + while (compiler.getSourceManager().isMacroArgExpansion(loc2)) { + loc2 = compiler.getSourceManager() + .getImmediateMacroCallerLoc(loc2); + } + if (compiler.getSourceManager().isMacroBodyExpansion(loc2)) { + //TODO: check loc, loc2 are in same macro body expansion + loc = compiler.getSourceManager().getSpellingLoc(loc); + } + } + auto s = compiler.getSourceManager().getCharacterData(loc); + auto n = Lexer::MeasureTokenLength( + loc, compiler.getSourceManager(), compiler.getLangOpts()); + std::string tok(s, n); + if (tok == "reinterpret_cast" && replaceText(loc, n, "static_cast")) + { + return true; + } + } + report( + DiagnosticsEngine::Warning, + "reinterpret_cast from %0 to %1 can be simplified to static_cast", + expr->getExprLoc()) + << expr->getSubExprAsWritten()->getType() << expr->getType() + << expr->getSourceRange(); + } else if (expr->getType()->isVoidPointerType()) { + auto t = expr->getSubExpr()->getType()->getAs<clang::PointerType>(); + if (t == nullptr || !t->getPointeeType()->isObjectType()) { + return true; + } + report( + DiagnosticsEngine::Warning, + ("reinterpret_cast from %0 to %1 can be simplified to static_cast" + " or an implicit conversion"), + expr->getExprLoc()) + << expr->getSubExprAsWritten()->getType() << expr->getType() + << expr->getSourceRange(); + } else if (expr->getType()->isFundamentalType()) { + if (auto const sub = dyn_cast<CXXConstCastExpr>( + expr->getSubExpr()->IgnoreParens())) + { + report( + DiagnosticsEngine::Warning, + ("redundant const_cast from %0 to %1 within reinterpret_cast to" + " fundamental type %2"), + expr->getExprLoc()) + << sub->getSubExprAsWritten()->getType() + << sub->getTypeAsWritten() << expr->getTypeAsWritten() + << expr->getSourceRange(); + return true; + } + } + return true; +} + +bool RedundantCast::VisitCXXConstCastExpr(CXXConstCastExpr const * expr) { + if (ignoreLocation(expr)) { + return true; + } + auto const sub = compat::getSubExprAsWritten(expr); + if (isRedundantConstCast(expr)) { + report( + DiagnosticsEngine::Warning, + "redundant const_cast from %0 %1 to %2 %3", expr->getExprLoc()) + << sub->getType() << printExprValueKind(sub->getValueKind()) + << expr->getTypeAsWritten() + << printExprValueKind(expr->getValueKind()) + << expr->getSourceRange(); + return true; + } + if (auto const dce = dyn_cast<CXXStaticCastExpr>( + sub->IgnoreParenImpCasts())) + { + auto const sub2 = compat::getSubExprAsWritten(dce); + auto t1 = sub2->getType().getCanonicalType(); + auto isNullptr = t1->isNullPtrType(); + auto t2 = dce->getType().getCanonicalType(); + auto t3 = expr->getType().getCanonicalType(); + auto redundant = false; + for (;;) { + if ((t2.isConstQualified() + && (isNullptr || !t1.isConstQualified()) + && !t3.isConstQualified()) + || (t2.isVolatileQualified() + && (isNullptr || !t1.isVolatileQualified()) + && !t3.isVolatileQualified())) + { + redundant = true; + break; + } + if (!isNullptr) { + auto const p1 = t1->getAs<clang::PointerType>(); + if (p1 == nullptr) { + break; + } + t1 = p1->getPointeeType(); + isNullptr = t1->isNullPtrType(); + } + auto const p2 = t2->getAs<clang::PointerType>(); + if (p2 == nullptr) { + break; + } + t2 = p2->getPointeeType(); + auto const p3 = t3->getAs<clang::PointerType>(); + if (p3 == nullptr) { + break; + } + t3 = p3->getPointeeType(); + } + if (redundant) { + report( + DiagnosticsEngine::Warning, + ("redundant static_cast/const_cast combination from %0 via %1" + " to %2"), + expr->getExprLoc()) + << sub2->getType() << dce->getTypeAsWritten() + << expr->getTypeAsWritten() << expr->getSourceRange(); + } + } + return true; +} + +bool RedundantCast::VisitCXXFunctionalCastExpr(CXXFunctionalCastExpr const * expr) { + if (ignoreLocation(expr)) { + return true; + } + // Restrict this to "real" casts (compared to uses of braced-init-list, like + // + // Foo{bar, baz} + // + // or + // + // std::initializer_list<Foo>{bar, baz} + // + // ), and only to cases where the sub-expression already is a prvalue of + // non-class type (and thus the cast is unlikely to be meant to create a + // temporary): + auto const t1 = expr->getTypeAsWritten(); + bool const fnptr = t1->isFunctionPointerType() || t1->isMemberFunctionPointerType(); + auto const sub = fnptr ? stopAtFunctionPointerDecay(expr) : compat::getSubExprAsWritten(expr); + if ((sub->getValueKind() != compat::VK_PRValue && !fnptr) || expr->getType()->isRecordType() + || isa<InitListExpr>(sub) || isa<CXXStdInitializerListExpr>(sub)) + { + return true; + } + + // See "There might even be good reasons(?) not to warn inside explicit + // casts" block in compilerplugins/clang/test/cppunitassertequals.cxx: + auto const eloc = expr->getExprLoc(); + if (compiler.getSourceManager().isMacroArgExpansion(eloc)) { + auto const name = Lexer::getImmediateMacroName( + eloc, compiler.getSourceManager(), compiler.getLangOpts()); + if (name == "CPPUNIT_ASSERT" || name == "CPPUNIT_ASSERT_MESSAGE") { + return true; + } + } + + // Don't warn if a functional cast on a pointer to function or member function is used to + // disambiguate an overloaded function: + if (fnptr) { + auto e = sub->IgnoreParenImpCasts(); + if (auto const e1 = dyn_cast<UnaryOperator>(e)) { + if (e1->getOpcode() == UO_AddrOf) { + e = e1->getSubExpr()->IgnoreParenImpCasts(); + } + } + if (auto const e1 = dyn_cast<DeclRefExpr>(e)) { + if (auto const fdecl = dyn_cast<FunctionDecl>(e1->getDecl())) { + if (isOverloadedFunction(fdecl)) { + return true; + } + } + } + } + + // See the commit message of d0e7d020fa405ab94f19916ec96fbd4611da0031 + // "socket.c -> socket.cxx" for the reason to have + // + // bool(FD_ISSET(...)) + // + // in sal/osl/unx/socket.cxx: + //TODO: Better check that sub is exactly an expansion of FD_ISSET: + if (sub->getEndLoc().isMacroID()) { + for (auto loc = sub->getBeginLoc(); + loc.isMacroID() + && (compiler.getSourceManager() + .isAtStartOfImmediateMacroExpansion(loc)); + loc = compiler.getSourceManager().getImmediateMacroCallerLoc(loc)) + { + if (Lexer::getImmediateMacroName( + loc, compiler.getSourceManager(), compiler.getLangOpts()) + == "FD_ISSET") + { + return true; + } + } + } + + auto const t2 = sub->getType(); + if (t1.getCanonicalType() != t2.getCanonicalType()) + return true; + if (!loplugin::isOkToRemoveArithmeticCast(compiler.getASTContext(), t1, t2, expr->getSubExpr())) + return true; + report( + DiagnosticsEngine::Warning, + "redundant functional cast from %0 to %1", expr->getExprLoc()) + << t2 << t1 << expr->getSourceRange(); + return true; +} + +bool RedundantCast::VisitCXXDynamicCastExpr(CXXDynamicCastExpr const * expr) { + if (ignoreLocation(expr)) { + return true; + } + auto const sub = compat::getSubExprAsWritten(expr); + auto const t1 = expr->getTypeAsWritten(); + auto const t2 = sub->getType(); + QualType qt1 = t1.getCanonicalType(); + QualType qt2 = t2.getCanonicalType(); + if (qt1 == qt2) + { + report( + DiagnosticsEngine::Warning, + "redundant dynamic cast from %0 to %1", expr->getExprLoc()) + << t2 << t1 << expr->getSourceRange(); + return true; + } + if (qt1->isPointerType() && qt2->isPointerType()) + { + // casting from 'T*' to 'const T*' is redundant, so compare without the qualifiers + qt1 = qt1->getPointeeType().getUnqualifiedType(); + qt2 = qt2->getPointeeType().getUnqualifiedType(); + if (qt1 == qt2) + { + report( + DiagnosticsEngine::Warning, + "redundant dynamic cast from %0 to %1", expr->getExprLoc()) + << t2 << t1 << expr->getSourceRange(); + return true; + } + if (qt1->getAsCXXRecordDecl() && qt2->getAsCXXRecordDecl()->isDerivedFrom(qt1->getAsCXXRecordDecl())) + { + report( + DiagnosticsEngine::Warning, + "redundant dynamic upcast from %0 to %1", expr->getExprLoc()) + << t2 << t1 << expr->getSourceRange(); + return true; + } + } + return true; +} + +bool RedundantCast::VisitCallExpr(CallExpr const * expr) { + if (ignoreLocation(expr)) { + return true; + } + auto f = expr->getDirectCallee(); + if (f == nullptr || !f->isVariadic() + || expr->getNumArgs() <= f->getNumParams()) + { + return true; + } + for (auto i = f->getNumParams(); i != expr->getNumArgs(); ++i) { + auto a = expr->getArg(i); + if (a->getType()->isPointerType()) { + auto e = dyn_cast<CXXConstCastExpr>(a->IgnoreParenImpCasts()); + if (e != nullptr) { + report( + DiagnosticsEngine::Warning, + "redundant const_cast of variadic function argument", + e->getExprLoc()) + << expr->getSourceRange(); + } + } + } + return true; +} + +bool RedundantCast::VisitCXXDeleteExpr(CXXDeleteExpr const * expr) { + if (ignoreLocation(expr)) { + return true; + } + auto e = dyn_cast<CXXConstCastExpr>( + expr->getArgument()->IgnoreParenImpCasts()); + if (e != nullptr) { + report( + DiagnosticsEngine::Warning, + "redundant const_cast in delete expression", e->getExprLoc()) + << expr->getSourceRange(); + } + return true; +} + +bool RedundantCast::visitBinOp(BinaryOperator const * expr) { + if (ignoreLocation(expr)) { + return true; + } + if (expr->getLHS()->getType()->isPointerType() + && expr->getRHS()->getType()->isPointerType()) + { + auto e = dyn_cast<CXXConstCastExpr>( + expr->getLHS()->IgnoreParenImpCasts()); + if (e != nullptr) { + report( + DiagnosticsEngine::Warning, + "redundant const_cast on lhs of pointer %select{comparison|subtraction}0 expression", + e->getExprLoc()) + << (expr->getOpcode() == BO_Sub) << expr->getSourceRange(); + } + e = dyn_cast<CXXConstCastExpr>( + expr->getRHS()->IgnoreParenImpCasts()); + if (e != nullptr) { + report( + DiagnosticsEngine::Warning, + "redundant const_cast on rhs of pointer %select{comparison|subtraction}0 expression", + e->getExprLoc()) + << (expr->getOpcode() == BO_Sub) << expr->getSourceRange(); + } + } + return true; +} + +bool RedundantCast::isOverloadedFunction(FunctionDecl const * decl) { + auto const ctx = decl->getDeclContext(); + if (!ctx->isLookupContext()) { + return false; + } + auto const canon = decl->getCanonicalDecl(); + auto const res = ctx->lookup(decl->getDeclName()); + for (auto d = res.begin(); d != res.end(); ++d) { + if (auto const f = dyn_cast<FunctionDecl>(*d)) { + if (f->getCanonicalDecl() != canon) { + return true; + } + } + } + return false; +} + +loplugin::Plugin::Registration<RedundantCast> X("redundantcast", true); + +} + +/* vim:set shiftwidth=4 softtabstop=4 expandtab: */ |