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Diffstat (limited to 'compilerplugins/clang/unsignedcompare.cxx')
| -rw-r--r-- | compilerplugins/clang/unsignedcompare.cxx | 232 |
1 files changed, 232 insertions, 0 deletions
diff --git a/compilerplugins/clang/unsignedcompare.cxx b/compilerplugins/clang/unsignedcompare.cxx new file mode 100644 index 000000000..5b55edea2 --- /dev/null +++ b/compilerplugins/clang/unsignedcompare.cxx @@ -0,0 +1,232 @@ +/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4; fill-column: 100 -*- */ +/* + * 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/. + */ + +#ifndef LO_CLANG_SHARED_PLUGINS + +// Find explicit casts from signed to unsigned integer in comparison against unsigned integer, where +// the cast is presumably used to avoid warnings about signed vs. unsigned comparisons, and could +// thus be replaced with o3tl::make_unsigned for clarity. + +#include <cassert> + +#include "plugin.hxx" + +namespace +{ +// clang::Type::isSignedIntegerType returns true for more types than what C++ defines as signed +// integer types: +bool isSignedIntegerType(QualType type) +{ + if (auto const t = type->getAs<BuiltinType>()) + { + // Assumes that the only extended signed integer type supported by Clang is Int128: + switch (t->getKind()) + { + case BuiltinType::SChar: + case BuiltinType::Short: + case BuiltinType::Int: + case BuiltinType::Long: + case BuiltinType::LongLong: + case BuiltinType::Int128: + return true; + default: + break; + } + } + return false; +} + +// clang::Type::isUnsignedIntegerType returns true for more types than what C++ defines as signed +// integer types: +bool isUnsignedIntegerType(QualType type) +{ + if (auto const t = type->getAs<BuiltinType>()) + { + // Assumes that the only extended unsigned integer type supported by Clang is UInt128: + switch (t->getKind()) + { + case BuiltinType::UChar: + case BuiltinType::UShort: + case BuiltinType::UInt: + case BuiltinType::ULong: + case BuiltinType::ULongLong: + case BuiltinType::UInt128: + return true; + default: + break; + } + } + return false; +} + +int getRank(QualType type) +{ + auto const t = type->getAs<BuiltinType>(); + assert(t != nullptr); + // Assumes that the only extended signed/unsigned integer types supported by Clang are Int128 + // and UInt128: + switch (t->getKind()) + { + case BuiltinType::SChar: + case BuiltinType::UChar: + return 0; + case BuiltinType::Short: + case BuiltinType::UShort: + return 1; + case BuiltinType::Int: + case BuiltinType::UInt: + return 2; + case BuiltinType::Long: + case BuiltinType::ULong: + return 3; + case BuiltinType::LongLong: + case BuiltinType::ULongLong: + return 4; + case BuiltinType::Int128: + case BuiltinType::UInt128: + return 5; + default: + llvm_unreachable("bad integer type"); + } +} + +int orderTypes(QualType type1, QualType type2) +{ + auto const r1 = getRank(type1); + auto const r2 = getRank(type2); + return r1 < r2 ? -1 : r1 == r2 ? 0 : 1; +} + +class UnsignedCompare : public loplugin::FilteringPlugin<UnsignedCompare> +{ +public: + explicit UnsignedCompare(loplugin::InstantiationData const& data) + : FilteringPlugin(data) + { + } + + bool VisitBinaryOperator(BinaryOperator const* expr) + { + if (ignoreLocation(expr)) + { + return true; + } + // o3tl::make_unsigned requires its argument to be non-negative, but this plugin doesn't + // check that when it reports its finding, so will produce false positives when the cast is + // actually meant to e.g. clamp from a large signed type to a small unsigned type. The + // assumption is that this will only be likely the case for BO_EQ (==) and BO_NE (!=) + // comparisons, so filter these out here (not sure what case BO_Cmp (<=>) will turn out to + // be, so lets keep it here at least for now): + switch (expr->getOpcode()) + { + case BO_Cmp: + case BO_LT: + case BO_GT: + case BO_LE: + case BO_GE: + break; + default: + return true; + } + auto const castL = isCastToUnsigned(expr->getLHS()); + auto const castR = isCastToUnsigned(expr->getRHS()); + //TODO(?): Also report somewhat suspicious cases where both sides are cast to unsigned: + if ((castL == nullptr) == (castR == nullptr)) + { + return true; + } + auto const cast = castL != nullptr ? castL : castR; + auto const other = castL != nullptr ? expr->getRHS() : expr->getLHS(); + auto const otherT = other->IgnoreImpCasts()->getType(); + if (!isUnsignedIntegerType(otherT)) + { + return true; + } + auto const castFromT = cast->getSubExprAsWritten()->getType(); + auto const castToT = cast->getTypeAsWritten(); + report(DiagnosticsEngine::Warning, + "explicit cast from %0 to %1 (of %select{smaller|equal|larger}2 rank) in comparison " + "against %3: if the cast value is known to be non-negative, use o3tl::make_unsigned " + "instead of the cast", + cast->getExprLoc()) + << castFromT << castToT << (orderTypes(castToT, castFromT) + 1) << otherT + << expr->getSourceRange(); + return true; + } + + bool preRun() override + { + return compiler.getLangOpts().CPlusPlus + && compiler.getPreprocessor() + .getIdentifierInfo("LIBO_INTERNAL_ONLY") + ->hasMacroDefinition(); + } + + void run() override + { + if (preRun()) + { + TraverseDecl(compiler.getASTContext().getTranslationUnitDecl()); + } + } + +private: + ExplicitCastExpr const* isCastToUnsigned(Expr const* expr) + { + auto const e = dyn_cast<ExplicitCastExpr>(expr->IgnoreParenImpCasts()); + if (e == nullptr) + { + return nullptr; + } + auto const t1 = e->getTypeAsWritten(); + if (!isUnsignedIntegerType(t1)) + { + return nullptr; + } + auto const e2 = e->getSubExprAsWritten(); + auto const t2 = e2->getType(); + if (!isSignedIntegerType(t2)) + { + return nullptr; + } + // Filter out e.g. `size_t(-1)`: + if (!e2->isValueDependent()) + { + if (auto const val = e2->getIntegerConstantExpr(compiler.getASTContext())) + { + if (val->isNegative()) + { + return nullptr; + } + } + } + auto loc = e->getBeginLoc(); + while (compiler.getSourceManager().isMacroArgExpansion(loc)) + { + loc = compiler.getSourceManager().getImmediateMacroCallerLoc(loc); + } + // This covers both "plain" code in such include files, as well as expansion of (object-like) macros like + // + // #define SAL_MAX_INT8 ((sal_Int8) 0x7F) + // + // defined in such include files: + if (isInUnoIncludeFile(compiler.getSourceManager().getSpellingLoc(loc))) + { //TODO: '#ifdef LIBO_INTERNAL_ONLY' within UNO include files + return nullptr; + } + return e; + } +}; + +loplugin::Plugin::Registration<UnsignedCompare> unsignedcompare("unsignedcompare"); +} + +#endif // LO_CLANG_SHARED_PLUGINS + +/* vim:set shiftwidth=4 softtabstop=4 expandtab cinoptions=b1,g0,N-s cinkeys+=0=break: */ |