clang-tools 20.0.0git
IncorrectRoundingsCheck.cpp
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1//===--- IncorrectRoundingsCheck.cpp - clang-tidy ------------------------------===//
2//
3// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4// See https://llvm.org/LICENSE.txt for license information.
5// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6//
7//===----------------------------------------------------------------------===//
8
10#include "clang/AST/DeclBase.h"
11#include "clang/AST/Type.h"
12#include "clang/ASTMatchers/ASTMatchFinder.h"
13#include "clang/ASTMatchers/ASTMatchers.h"
14#include "clang/Lex/Lexer.h"
15
16using namespace clang::ast_matchers;
17
18namespace clang::tidy::bugprone {
19
20static llvm::APFloat getHalf(const llvm::fltSemantics &Semantics) {
21 return llvm::APFloat(Semantics, 1U) / llvm::APFloat(Semantics, 2U);
22}
23
24namespace {
25AST_MATCHER(FloatingLiteral, floatHalf) {
26 return Node.getValue() == getHalf(Node.getSemantics());
27}
28} // namespace
29
30void IncorrectRoundingsCheck::registerMatchers(MatchFinder *MatchFinder) {
31 // Match a floating literal with value 0.5.
32 auto FloatHalf = floatLiteral(floatHalf());
33
34 // Match a floating point expression.
35 auto FloatType = expr(hasType(realFloatingPointType()));
36
37 // Find expressions of cast to int of the sum of a floating point expression
38 // and 0.5.
39 MatchFinder->addMatcher(
40 traverse(TK_AsIs,
41 implicitCastExpr(
42 hasImplicitDestinationType(isInteger()),
43 ignoringParenCasts(binaryOperator(
44 hasOperatorName("+"), hasOperands(FloatType, FloatType),
45 hasEitherOperand(ignoringParenImpCasts(FloatHalf)))))
46 .bind("CastExpr")),
47 this);
48}
49
50void IncorrectRoundingsCheck::check(const MatchFinder::MatchResult &Result) {
51 const auto *CastExpr = Result.Nodes.getNodeAs<ImplicitCastExpr>("CastExpr");
52 diag(CastExpr->getBeginLoc(),
53 "casting (double + 0.5) to integer leads to incorrect rounding; "
54 "consider using lround (#include <cmath>) instead");
55}
56
57} // namespace clang::tidy::bugprone
::clang::DynTypedNode Node
DiagnosticBuilder diag(SourceLocation Loc, StringRef Description, DiagnosticIDs::Level Level=DiagnosticIDs::Warning)
Add a diagnostic with the check's name.
void registerMatchers(ast_matchers::MatchFinder *Finder) override
Override this to register AST matchers with Finder.
void check(const ast_matchers::MatchFinder::MatchResult &Result) override
ClangTidyChecks that register ASTMatchers should do the actual work in here.
static llvm::APFloat getHalf(const llvm::fltSemantics &Semantics)
AST_MATCHER(clang::VarDecl, hasConstantDeclaration)