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llvm-project/clang-tools-extra/clang-tidy/cppcoreguidelines/NarrowingConversionsCheck.cpp

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//===--- NarrowingConversionsCheck.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 "NarrowingConversionsCheck.h"
#include "clang/AST/ASTContext.h"
#include "clang/AST/Type.h"
#include "clang/ASTMatchers/ASTMatchFinder.h"
#include "llvm/ADT/APSInt.h"
#include "llvm/ADT/SmallString.h"
#include "llvm/ADT/SmallVector.h"
#include <cstdint>
using namespace clang::ast_matchers;
namespace clang {
namespace tidy {
namespace cppcoreguidelines {
NarrowingConversionsCheck::NarrowingConversionsCheck(StringRef Name,
ClangTidyContext *Context)
: ClangTidyCheck(Name, Context),
WarnOnFloatingPointNarrowingConversion(
Options.get("WarnOnFloatingPointNarrowingConversion", 1)),
PedanticMode(Options.get("PedanticMode", 0)) {}
void NarrowingConversionsCheck::registerMatchers(MatchFinder *Finder) {
// ceil() and floor() are guaranteed to return integers, even though the type
// is not integral.
const auto IsCeilFloorCallExpr = expr(callExpr(callee(functionDecl(
hasAnyName("::ceil", "::std::ceil", "::floor", "::std::floor")))));
// Casts:
// i = 0.5;
// void f(int); f(0.5);
Finder->addMatcher(
implicitCastExpr(hasImplicitDestinationType(builtinType()),
hasSourceExpression(hasType(builtinType())),
unless(hasSourceExpression(IsCeilFloorCallExpr)),
unless(hasParent(castExpr())),
unless(isInTemplateInstantiation()))
.bind("cast"),
this);
// Binary operators:
// i += 0.5;
Finder->addMatcher(binaryOperator(isAssignmentOperator(),
hasLHS(expr(hasType(builtinType()))),
hasRHS(expr(hasType(builtinType()))),
unless(hasRHS(IsCeilFloorCallExpr)),
unless(isInTemplateInstantiation()),
// The `=` case generates an implicit cast
// which is covered by the previous matcher.
unless(hasOperatorName("=")))
.bind("binary_op"),
this);
}
static const BuiltinType *getBuiltinType(const Expr &E) {
return E.getType().getCanonicalType().getTypePtr()->getAs<BuiltinType>();
}
static QualType getUnqualifiedType(const Expr &E) {
return E.getType().getUnqualifiedType();
}
static APValue getConstantExprValue(const ASTContext &Ctx, const Expr &E) {
llvm::APSInt IntegerConstant;
if (E.isIntegerConstantExpr(IntegerConstant, Ctx))
return APValue(IntegerConstant);
APValue Constant;
if (Ctx.getLangOpts().CPlusPlus && E.isCXX11ConstantExpr(Ctx, &Constant))
return Constant;
return {};
}
static bool getIntegerConstantExprValue(const ASTContext &Context,
const Expr &E, llvm::APSInt &Value) {
APValue Constant = getConstantExprValue(Context, E);
if (!Constant.isInt())
return false;
Value = Constant.getInt();
return true;
}
static bool getFloatingConstantExprValue(const ASTContext &Context,
const Expr &E, llvm::APFloat &Value) {
APValue Constant = getConstantExprValue(Context, E);
if (!Constant.isFloat())
return false;
Value = Constant.getFloat();
return true;
}
namespace {
struct IntegerRange {
bool Contains(const IntegerRange &From) const {
return llvm::APSInt::compareValues(Lower, From.Lower) <= 0 &&
llvm::APSInt::compareValues(Upper, From.Upper) >= 0;
}
bool Contains(const llvm::APSInt &Value) const {
return llvm::APSInt::compareValues(Lower, Value) <= 0 &&
llvm::APSInt::compareValues(Upper, Value) >= 0;
}
llvm::APSInt Lower;
llvm::APSInt Upper;
};
} // namespace
static IntegerRange createFromType(const ASTContext &Context,
const BuiltinType &T) {
if (T.isFloatingPoint()) {
unsigned PrecisionBits = llvm::APFloatBase::semanticsPrecision(
Context.getFloatTypeSemantics(T.desugar()));
// Contrary to two's complement integer, floating point values are
// symmetric and have the same number of positive and negative values.
// The range of valid integers for a floating point value is:
// [-2^PrecisionBits, 2^PrecisionBits]
// Values are created with PrecisionBits plus two bits:
// - One to express the missing negative value of 2's complement
// representation.
// - One for the sign.
llvm::APSInt UpperValue(PrecisionBits + 2, /*isUnsigned*/ false);
UpperValue.setBit(PrecisionBits);
llvm::APSInt LowerValue(PrecisionBits + 2, /*isUnsigned*/ false);
LowerValue.setBit(PrecisionBits);
LowerValue.setSignBit();
return {LowerValue, UpperValue};
}
assert(T.isInteger() && "Unexpected builtin type");
uint64_t TypeSize = Context.getTypeSize(&T);
bool IsUnsignedInteger = T.isUnsignedInteger();
return {llvm::APSInt::getMinValue(TypeSize, IsUnsignedInteger),
llvm::APSInt::getMaxValue(TypeSize, IsUnsignedInteger)};
}
static bool isWideEnoughToHold(const ASTContext &Context,
const BuiltinType &FromType,
const BuiltinType &ToType) {
IntegerRange FromIntegerRange = createFromType(Context, FromType);
IntegerRange ToIntegerRange = createFromType(Context, ToType);
return ToIntegerRange.Contains(FromIntegerRange);
}
static bool isWideEnoughToHold(const ASTContext &Context,
const llvm::APSInt &IntegerConstant,
const BuiltinType &ToType) {
IntegerRange ToIntegerRange = createFromType(Context, ToType);
return ToIntegerRange.Contains(IntegerConstant);
}
static llvm::SmallString<64> getValueAsString(const llvm::APSInt &Value,
uint64_t HexBits) {
llvm::SmallString<64> Str;
Value.toString(Str, 10);
if (HexBits > 0) {
Str.append(" (0x");
llvm::SmallString<32> HexValue;
Value.toStringUnsigned(HexValue, 16);
for (size_t I = HexValue.size(); I < (HexBits / 4); ++I)
Str.append("0");
Str.append(HexValue);
Str.append(")");
}
return Str;
}
void NarrowingConversionsCheck::diagNarrowType(SourceLocation SourceLoc,
const Expr &Lhs,
const Expr &Rhs) {
diag(SourceLoc, "narrowing conversion from %0 to %1")
<< getUnqualifiedType(Rhs) << getUnqualifiedType(Lhs);
}
void NarrowingConversionsCheck::diagNarrowTypeToSignedInt(
SourceLocation SourceLoc, const Expr &Lhs, const Expr &Rhs) {
diag(SourceLoc, "narrowing conversion from %0 to signed type %1 is "
"implementation-defined")
<< getUnqualifiedType(Rhs) << getUnqualifiedType(Lhs);
}
void NarrowingConversionsCheck::diagNarrowIntegerConstant(
SourceLocation SourceLoc, const Expr &Lhs, const Expr &Rhs,
const llvm::APSInt &Value) {
diag(SourceLoc,
"narrowing conversion from constant value %0 of type %1 to %2")
<< getValueAsString(Value, /*NoHex*/ 0) << getUnqualifiedType(Rhs)
<< getUnqualifiedType(Lhs);
}
void NarrowingConversionsCheck::diagNarrowIntegerConstantToSignedInt(
SourceLocation SourceLoc, const Expr &Lhs, const Expr &Rhs,
const llvm::APSInt &Value, const uint64_t HexBits) {
diag(SourceLoc, "narrowing conversion from constant value %0 of type %1 "
"to signed type %2 is implementation-defined")
<< getValueAsString(Value, HexBits) << getUnqualifiedType(Rhs)
<< getUnqualifiedType(Lhs);
}
void NarrowingConversionsCheck::diagNarrowConstant(SourceLocation SourceLoc,
const Expr &Lhs,
const Expr &Rhs) {
diag(SourceLoc, "narrowing conversion from constant %0 to %1")
<< getUnqualifiedType(Rhs) << getUnqualifiedType(Lhs);
}
void NarrowingConversionsCheck::diagConstantCast(SourceLocation SourceLoc,
const Expr &Lhs,
const Expr &Rhs) {
diag(SourceLoc, "constant value should be of type of type %0 instead of %1")
<< getUnqualifiedType(Lhs) << getUnqualifiedType(Rhs);
}
void NarrowingConversionsCheck::diagNarrowTypeOrConstant(
const ASTContext &Context, SourceLocation SourceLoc, const Expr &Lhs,
const Expr &Rhs) {
APValue Constant = getConstantExprValue(Context, Rhs);
if (Constant.isInt())
return diagNarrowIntegerConstant(SourceLoc, Lhs, Rhs, Constant.getInt());
if (Constant.isFloat())
return diagNarrowConstant(SourceLoc, Lhs, Rhs);
return diagNarrowType(SourceLoc, Lhs, Rhs);
}
void NarrowingConversionsCheck::handleIntegralCast(const ASTContext &Context,
SourceLocation SourceLoc,
const Expr &Lhs,
const Expr &Rhs) {
const BuiltinType *ToType = getBuiltinType(Lhs);
// From [conv.integral]p7.3.8:
// Conversions to unsigned integer is well defined so no warning is issued.
// "The resulting value is the smallest unsigned value equal to the source
// value modulo 2^n where n is the number of bits used to represent the
// destination type."
if (ToType->isUnsignedInteger())
return;
const BuiltinType *FromType = getBuiltinType(Rhs);
llvm::APSInt IntegerConstant;
if (getIntegerConstantExprValue(Context, Rhs, IntegerConstant)) {
if (!isWideEnoughToHold(Context, IntegerConstant, *ToType))
diagNarrowIntegerConstantToSignedInt(SourceLoc, Lhs, Rhs, IntegerConstant,
Context.getTypeSize(FromType));
return;
}
if (!isWideEnoughToHold(Context, *FromType, *ToType))
diagNarrowTypeToSignedInt(SourceLoc, Lhs, Rhs);
}
void NarrowingConversionsCheck::handleIntegralToBoolean(
const ASTContext &Context, SourceLocation SourceLoc, const Expr &Lhs,
const Expr &Rhs) {
// Conversion from Integral to Bool value is well defined.
// We keep this function (even if it is empty) to make sure that
// handleImplicitCast and handleBinaryOperator are symmetric in their behavior
// and handle the same cases.
}
void NarrowingConversionsCheck::handleIntegralToFloating(
const ASTContext &Context, SourceLocation SourceLoc, const Expr &Lhs,
const Expr &Rhs) {
const BuiltinType *ToType = getBuiltinType(Lhs);
llvm::APSInt IntegerConstant;
if (getIntegerConstantExprValue(Context, Rhs, IntegerConstant)) {
if (!isWideEnoughToHold(Context, IntegerConstant, *ToType))
diagNarrowIntegerConstant(SourceLoc, Lhs, Rhs, IntegerConstant);
return;
}
const BuiltinType *FromType = getBuiltinType(Rhs);
if (!isWideEnoughToHold(Context, *FromType, *ToType))
diagNarrowType(SourceLoc, Lhs, Rhs);
}
void NarrowingConversionsCheck::handleFloatingToIntegral(
const ASTContext &Context, SourceLocation SourceLoc, const Expr &Lhs,
const Expr &Rhs) {
llvm::APFloat FloatConstant(0.0);
// We always warn when Rhs is non-constexpr.
if (!getFloatingConstantExprValue(Context, Rhs, FloatConstant))
return diagNarrowType(SourceLoc, Lhs, Rhs);
QualType DestType = Lhs.getType();
unsigned DestWidth = Context.getIntWidth(DestType);
bool DestSigned = DestType->isSignedIntegerOrEnumerationType();
llvm::APSInt Result = llvm::APSInt(DestWidth, !DestSigned);
bool IsExact = false;
bool Overflows = FloatConstant.convertToInteger(
Result, llvm::APFloat::rmTowardZero, &IsExact) &
llvm::APFloat::opInvalidOp;
// We warn iff the constant floating point value is not exactly representable.
if (Overflows || !IsExact)
return diagNarrowConstant(SourceLoc, Lhs, Rhs);
if (PedanticMode)
return diagConstantCast(SourceLoc, Lhs, Rhs);
}
void NarrowingConversionsCheck::handleFloatingToBoolean(
const ASTContext &Context, SourceLocation SourceLoc, const Expr &Lhs,
const Expr &Rhs) {
return diagNarrowTypeOrConstant(Context, SourceLoc, Lhs, Rhs);
}
void NarrowingConversionsCheck::handleBooleanToSignedIntegral(
const ASTContext &Context, SourceLocation SourceLoc, const Expr &Lhs,
const Expr &Rhs) {
// Conversion from Bool to SignedIntegral value is well defined.
// We keep this function (even if it is empty) to make sure that
// handleImplicitCast and handleBinaryOperator are symmetric in their behavior
// and handle the same cases.
}
void NarrowingConversionsCheck::handleFloatingCast(const ASTContext &Context,
SourceLocation SourceLoc,
const Expr &Lhs,
const Expr &Rhs) {
if (WarnOnFloatingPointNarrowingConversion) {
const BuiltinType *ToType = getBuiltinType(Lhs);
APValue Constant = getConstantExprValue(Context, Rhs);
if (Constant.isFloat()) {
// From [dcl.init.list]p7.2:
// Floating point constant narrowing only takes place when the value is
// not within destination range. We convert the value to the destination
// type and check if the resulting value is infinity.
llvm::APFloat Tmp = Constant.getFloat();
bool UnusedLosesInfo;
Tmp.convert(Context.getFloatTypeSemantics(ToType->desugar()),
llvm::APFloatBase::rmNearestTiesToEven, &UnusedLosesInfo);
if (Tmp.isInfinity())
diagNarrowConstant(SourceLoc, Lhs, Rhs);
return;
}
const BuiltinType *FromType = getBuiltinType(Rhs);
if (ToType->getKind() < FromType->getKind())
diagNarrowType(SourceLoc, Lhs, Rhs);
}
}
void NarrowingConversionsCheck::handleBinaryOperator(const ASTContext &Context,
SourceLocation SourceLoc,
const Expr &Lhs,
const Expr &Rhs) {
assert(!Lhs.isInstantiationDependent() && !Rhs.isInstantiationDependent() &&
"Dependent types must be check before calling this function");
const BuiltinType *LhsType = getBuiltinType(Lhs);
const BuiltinType *RhsType = getBuiltinType(Rhs);
if (RhsType == nullptr || LhsType == nullptr)
return;
if (RhsType->getKind() == BuiltinType::Bool && LhsType->isSignedInteger())
return handleBooleanToSignedIntegral(Context, SourceLoc, Lhs, Rhs);
if (RhsType->isInteger() && LhsType->getKind() == BuiltinType::Bool)
return handleIntegralToBoolean(Context, SourceLoc, Lhs, Rhs);
if (RhsType->isInteger() && LhsType->isFloatingPoint())
return handleIntegralToFloating(Context, SourceLoc, Lhs, Rhs);
if (RhsType->isInteger() && LhsType->isInteger())
return handleIntegralCast(Context, SourceLoc, Lhs, Rhs);
if (RhsType->isFloatingPoint() && LhsType->getKind() == BuiltinType::Bool)
return handleFloatingToBoolean(Context, SourceLoc, Lhs, Rhs);
if (RhsType->isFloatingPoint() && LhsType->isInteger())
return handleFloatingToIntegral(Context, SourceLoc, Lhs, Rhs);
if (RhsType->isFloatingPoint() && LhsType->isFloatingPoint())
return handleFloatingCast(Context, SourceLoc, Lhs, Rhs);
}
bool NarrowingConversionsCheck::handleConditionalOperator(
const ASTContext &Context, const Expr &Lhs, const Expr &Rhs) {
if (const auto *CO = llvm::dyn_cast<ConditionalOperator>(&Rhs)) {
// We have an expression like so: `output = cond ? lhs : rhs`
// From the point of view of narrowing conversion we treat it as two
// expressions `output = lhs` and `output = rhs`.
handleBinaryOperator(Context, CO->getLHS()->getExprLoc(), Lhs,
*CO->getLHS());
handleBinaryOperator(Context, CO->getRHS()->getExprLoc(), Lhs,
*CO->getRHS());
return true;
}
return false;
}
void NarrowingConversionsCheck::handleImplicitCast(
const ASTContext &Context, const ImplicitCastExpr &Cast) {
if (Cast.getExprLoc().isMacroID())
return;
const Expr &Lhs = Cast;
const Expr &Rhs = *Cast.getSubExpr();
if (Lhs.isInstantiationDependent() || Rhs.isInstantiationDependent())
return;
if (handleConditionalOperator(Context, Lhs, Rhs))
return;
SourceLocation SourceLoc = Lhs.getExprLoc();
switch (Cast.getCastKind()) {
case CK_BooleanToSignedIntegral:
return handleBooleanToSignedIntegral(Context, SourceLoc, Lhs, Rhs);
case CK_IntegralToBoolean:
return handleIntegralToBoolean(Context, SourceLoc, Lhs, Rhs);
case CK_IntegralToFloating:
return handleIntegralToFloating(Context, SourceLoc, Lhs, Rhs);
case CK_IntegralCast:
return handleIntegralCast(Context, SourceLoc, Lhs, Rhs);
case CK_FloatingToBoolean:
return handleFloatingToBoolean(Context, SourceLoc, Lhs, Rhs);
case CK_FloatingToIntegral:
return handleFloatingToIntegral(Context, SourceLoc, Lhs, Rhs);
case CK_FloatingCast:
return handleFloatingCast(Context, SourceLoc, Lhs, Rhs);
default:
break;
}
}
void NarrowingConversionsCheck::handleBinaryOperator(const ASTContext &Context,
const BinaryOperator &Op) {
if (Op.getBeginLoc().isMacroID())
return;
const Expr &Lhs = *Op.getLHS();
const Expr &Rhs = *Op.getRHS();
if (Lhs.isInstantiationDependent() || Rhs.isInstantiationDependent())
return;
if (handleConditionalOperator(Context, Lhs, Rhs))
return;
handleBinaryOperator(Context, Rhs.getBeginLoc(), Lhs, Rhs);
}
void NarrowingConversionsCheck::check(const MatchFinder::MatchResult &Result) {
if (const auto *Op = Result.Nodes.getNodeAs<BinaryOperator>("binary_op"))
return handleBinaryOperator(*Result.Context, *Op);
if (const auto *Cast = Result.Nodes.getNodeAs<ImplicitCastExpr>("cast"))
return handleImplicitCast(*Result.Context, *Cast);
llvm_unreachable("must be binary operator or cast expression");
}
} // namespace cppcoreguidelines
} // namespace tidy
} // namespace clang
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