IncorrectRoundingsCheck.cpp
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//===--- IncorrectRoundingsCheck.cpp - clang-tidy ------------------------------===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
#include "IncorrectRoundingsCheck.h"
#include "clang/AST/DeclBase.h"
#include "clang/AST/Type.h"
#include "clang/ASTMatchers/ASTMatchFinder.h"
#include "clang/ASTMatchers/ASTMatchers.h"
#include "clang/Lex/Lexer.h"
using namespace clang::ast_matchers;
namespace clang {
namespace tidy {
namespace bugprone {
namespace {
AST_MATCHER(FloatingLiteral, floatHalf) {
const auto &literal = Node.getValue();
if ((&Node.getSemantics()) == &llvm::APFloat::IEEEsingle())
return literal.convertToFloat() == 0.5f;
if ((&Node.getSemantics()) == &llvm::APFloat::IEEEdouble())
return literal.convertToDouble() == 0.5;
return false;
}
} // namespace
void IncorrectRoundingsCheck::registerMatchers(MatchFinder *MatchFinder) {
// Match a floating literal with value 0.5.
auto FloatHalf = floatLiteral(floatHalf());
// Match a floating point expression.
auto FloatType = expr(hasType(realFloatingPointType()));
// Match a floating literal of 0.5 or a floating literal of 0.5 implicitly.
// cast to floating type.
auto FloatOrCastHalf =
anyOf(FloatHalf,
implicitCastExpr(FloatType, has(ignoringParenImpCasts(FloatHalf))));
// Match if either the LHS or RHS is a floating literal of 0.5 or a floating
// literal of 0.5 and the other is of type double or vice versa.
auto OneSideHalf = anyOf(allOf(hasLHS(FloatOrCastHalf), hasRHS(FloatType)),
allOf(hasRHS(FloatOrCastHalf), hasLHS(FloatType)));
// Find expressions of cast to int of the sum of a floating point expression
// and 0.5.
MatchFinder->addMatcher(
implicitCastExpr(
hasImplicitDestinationType(isInteger()),
ignoringParenCasts(binaryOperator(hasOperatorName("+"), OneSideHalf)))
.bind("CastExpr"),
this);
}
void IncorrectRoundingsCheck::check(const MatchFinder::MatchResult &Result) {
const auto *CastExpr = Result.Nodes.getNodeAs<ImplicitCastExpr>("CastExpr");
diag(CastExpr->getBeginLoc(),
"casting (double + 0.5) to integer leads to incorrect rounding; "
"consider using lround (#include <cmath>) instead");
}
} // namespace bugprone
} // namespace tidy
} // namespace clang