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[clang-tidy] Misc redundant expressions check updated for overloaded operators 

Patch by: Lilla Barancsuk

Differential Revision: https://reviews.llvm.org/D39243

llvm-svn: 319033
This commit is contained in:
Gabor Horvath 2017-11-27 15:05:24 +00:00
parent 4164009b48
commit 250c40dc26
2 changed files with 168 additions and 22 deletions
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105
clang-tools-extra/clang-tidy/misc/RedundantExpressionCheck.cpp
View File

@ -98,6 +98,9 @@ static bool areEquivalentExpr(const Expr *Left, const Expr *Right) {
case Stmt::StringLiteralClass:
return cast<StringLiteral>(Left)->getBytes() ==
cast<StringLiteral>(Right)->getBytes();
case Stmt::CXXOperatorCallExprClass:
return cast<CXXOperatorCallExpr>(Left)->getOperator() ==
cast<CXXOperatorCallExpr>(Right)->getOperator();
case Stmt::DependentScopeDeclRefExprClass:
if (cast<DependentScopeDeclRefExpr>(Left)->getDeclName() !=
cast<DependentScopeDeclRefExpr>(Right)->getDeclName())
@ -410,6 +413,7 @@ matchRelationalIntegerConstantExpr(StringRef Id) {
std::string CastId = (Id + "-cast").str();
std::string SwapId = (Id + "-swap").str();
std::string NegateId = (Id + "-negate").str();
std::string OverloadId = (Id + "-overload").str();
const auto RelationalExpr = ignoringParenImpCasts(binaryOperator(
isComparisonOperator(), expr().bind(Id),
@ -437,12 +441,54 @@ matchRelationalIntegerConstantExpr(StringRef Id) {
hasOperatorName("!"),
hasUnaryOperand(anyOf(CastExpr, RelationalExpr)))));
const auto OverloadedOperatorExpr =
cxxOperatorCallExpr(
anyOf(hasOverloadedOperatorName("=="),
hasOverloadedOperatorName("!="), hasOverloadedOperatorName("<"),
hasOverloadedOperatorName("<="), hasOverloadedOperatorName(">"),
hasOverloadedOperatorName(">=")),
// Filter noisy false positives.
unless(isMacro()), unless(isInTemplateInstantiation()))
.bind(OverloadId);
return anyOf(RelationalExpr, CastExpr, NegateRelationalExpr,
NegateNegateRelationalExpr);
NegateNegateRelationalExpr, OverloadedOperatorExpr);
}
// Retrieves sub-expressions matched by 'matchRelationalIntegerConstantExpr' with
// name 'Id'.
// Checks whether a function param is non constant reference type, and may
// be modified in the function.
static bool isNonConstReferenceType(QualType ParamType) {
return ParamType->isReferenceType() &&
!ParamType.getNonReferenceType().isConstQualified();
}
// Checks whether the arguments of an overloaded operator can be modified in the
// function.
// For operators that take an instance and a constant as arguments, only the
// first argument (the instance) needs to be checked, since the constant itself
// is a temporary expression. Whether the second parameter is checked is
// controlled by the parameter `ParamsToCheckCount`.
static bool
canOverloadedOperatorArgsBeModified(const FunctionDecl *OperatorDecl,
bool checkSecondParam) {
unsigned ParamCount = OperatorDecl->getNumParams();
// Overloaded operators declared inside a class have only one param.
// These functions must be declared const in order to not be able to modify
// the instance of the class they are called through.
if (ParamCount == 1 &&
!OperatorDecl->getType()->getAs<FunctionType>()->isConst())
return true;
if (isNonConstReferenceType(OperatorDecl->getParamDecl(0)->getType()))
return true;
return checkSecondParam && ParamCount == 2 &&
isNonConstReferenceType(OperatorDecl->getParamDecl(1)->getType());
}
// Retrieves sub-expressions matched by 'matchRelationalIntegerConstantExpr'
// with name 'Id'.
static bool retrieveRelationalIntegerConstantExpr(
const MatchFinder::MatchResult &Result, StringRef Id,
const Expr *&OperandExpr, BinaryOperatorKind &Opcode, const Expr *&Symbol,
@ -450,6 +496,7 @@ static bool retrieveRelationalIntegerConstantExpr(
std::string CastId = (Id + "-cast").str();
std::string SwapId = (Id + "-swap").str();
std::string NegateId = (Id + "-negate").str();
std::string OverloadId = (Id + "-overload").str();
if (const auto *Bin = Result.Nodes.getNodeAs<BinaryOperator>(Id)) {
// Operand received with explicit comparator.
@ -458,12 +505,29 @@ static bool retrieveRelationalIntegerConstantExpr(
if (!retrieveIntegerConstantExpr(Result, Id, Value, ConstExpr))
return false;
} else if (const auto *Cast = Result.Nodes.getNodeAs<CastExpr>(CastId)) {
// Operand received with implicit comparator (cast).
Opcode = BO_NE;
OperandExpr = Cast;
Value = APSInt(32, false);
} else if (const auto *OverloadedOperatorExpr =
Result.Nodes.getNodeAs<CXXOperatorCallExpr>(OverloadId)) {
const auto *OverloadedFunctionDecl = dyn_cast_or_null<FunctionDecl>(OverloadedOperatorExpr->getCalleeDecl());
if (!OverloadedFunctionDecl)
return false;
if (canOverloadedOperatorArgsBeModified(OverloadedFunctionDecl, false))
return false;
if (!OverloadedOperatorExpr->getArg(1)->isIntegerConstantExpr(
Value, *Result.Context))
return false;
Symbol = OverloadedOperatorExpr->getArg(0);
OperandExpr = OverloadedOperatorExpr;
Opcode = BinaryOperator::getOverloadedOpcode(OverloadedOperatorExpr->getOperator());
return BinaryOperator::isComparisonOp(Opcode);
} else {
return false;
}
@ -548,7 +612,8 @@ static bool areExprsFromDifferentMacros(const Expr *LhsExpr,
Lexer::getImmediateMacroName(RhsLoc, SM, LO));
}
static bool areExprsMacroAndNonMacro(const Expr *&LhsExpr, const Expr *&RhsExpr) {
static bool areExprsMacroAndNonMacro(const Expr *&LhsExpr,
const Expr *&RhsExpr) {
if (!LhsExpr || !RhsExpr)
return false;
@ -562,7 +627,8 @@ void RedundantExpressionCheck::registerMatchers(MatchFinder *Finder) {
const auto AnyLiteralExpr = ignoringParenImpCasts(
anyOf(cxxBoolLiteral(), characterLiteral(), integerLiteral()));
const auto BannedIntegerLiteral = integerLiteral(expandedByMacro(KnownBannedMacroNames));
const auto BannedIntegerLiteral =
integerLiteral(expandedByMacro(KnownBannedMacroNames));
// Binary with equivalent operands, like (X != 2 && X != 2).
Finder->addMatcher(
@ -584,13 +650,12 @@ void RedundantExpressionCheck::registerMatchers(MatchFinder *Finder) {
this);
// Conditional (trenary) operator with equivalent operands, like (Y ? X : X).
Finder->addMatcher(
conditionalOperator(expressionsAreEquivalent(),
// Filter noisy false positives.
unless(conditionalOperatorIsInMacro()),
unless(isInTemplateInstantiation()))
.bind("cond"),
this);
Finder->addMatcher(conditionalOperator(expressionsAreEquivalent(),
// Filter noisy false positives.
unless(conditionalOperatorIsInMacro()),
unless(isInTemplateInstantiation()))
.bind("cond"),
this);
// Overloaded operators with equivalent operands.
Finder->addMatcher(
@ -821,16 +886,15 @@ void RedundantExpressionCheck::checkRelationalExpr(
void RedundantExpressionCheck::check(const MatchFinder::MatchResult &Result) {
if (const auto *BinOp = Result.Nodes.getNodeAs<BinaryOperator>("binary")) {
// If the expression's constants are macros, check whether they are
// intentional.
if (areSidesBinaryConstExpressions(BinOp, Result.Context)) {
const Expr *LhsConst = nullptr, *RhsConst = nullptr;
BinaryOperatorKind MainOpcode, SideOpcode;
if(!retrieveConstExprFromBothSides(BinOp, MainOpcode, SideOpcode, LhsConst,
RhsConst, Result.Context))
return;
if (!retrieveConstExprFromBothSides(BinOp, MainOpcode, SideOpcode,
LhsConst, RhsConst, Result.Context))
return;
if (areExprsFromDifferentMacros(LhsConst, RhsConst, Result.Context) ||
areExprsMacroAndNonMacro(LhsConst, RhsConst))
@ -853,6 +917,13 @@ void RedundantExpressionCheck::check(const MatchFinder::MatchResult &Result) {
}
if (const auto *Call = Result.Nodes.getNodeAs<CXXOperatorCallExpr>("call")) {
const auto *OverloadedFunctionDecl = dyn_cast_or_null<FunctionDecl>(Call->getCalleeDecl());
if (!OverloadedFunctionDecl)
return;
if (canOverloadedOperatorArgsBeModified(OverloadedFunctionDecl, true))
return;
diag(Call->getOperatorLoc(),
"both sides of overloaded operator are equivalent");
}

85
clang-tools-extra/test/clang-tidy/misc-redundant-expression.cpp
View File

@ -124,16 +124,36 @@ int TestConditional(int x, int y) {
#undef COND_OP_MACRO
#undef COND_OP_OTHER_MACRO
// Overloaded operators that compare two instances of a struct.
struct MyStruct {
int x;
int x;
bool operator==(const MyStruct& rhs) const {return this->x == rhs.x; } // not modifing
bool operator>=(const MyStruct& rhs) const { return this->x >= rhs.x; } // not modifing
bool operator<=(MyStruct& rhs) const { return this->x <= rhs.x; }
bool operator&&(const MyStruct& rhs){ this->x++; return this->x && rhs.x; }
} Q;
bool operator==(const MyStruct& lhs, const MyStruct& rhs) { return lhs.x == rhs.x; }
bool operator!=(const MyStruct& lhs, const MyStruct& rhs) { return lhs.x == rhs.x; } // not modifing
bool operator<(const MyStruct& lhs, const MyStruct& rhs) { return lhs.x < rhs.x; } // not modifing
bool operator>(const MyStruct& lhs, MyStruct& rhs) { rhs.x--; return lhs.x > rhs.x; }
bool operator||(MyStruct& lhs, const MyStruct& rhs) { lhs.x++; return lhs.x || rhs.x; }
bool TestOperator(MyStruct& S) {
bool TestOverloadedOperator(MyStruct& S) {
if (S == Q) return false;
if (S <= S) return false;
if (S && S) return false;
if (S > S) return false;
if (S || S) return false;
if (S == S) return true;
// CHECK-MESSAGES: :[[@LINE-1]]:9: warning: both sides of overloaded operator are equivalent
if (S < S) return true;
// CHECK-MESSAGES: :[[@LINE-1]]:9: warning: both sides of overloaded operator are equivalent
if (S != S) return true;
// CHECK-MESSAGES: :[[@LINE-1]]:9: warning: both sides of overloaded operator are equivalent
if (S >= S) return true;
// CHECK-MESSAGES: :[[@LINE-1]]:9: warning: both sides of overloaded operator are equivalent
}
#define LT(x, y) (void)((x) < (y))
@ -176,7 +196,7 @@ template <typename T, typename U>
void TemplateCheck() {
static_assert(T::Value == U::Value, "should be identical");
static_assert(T::Value == T::Value, "should be identical");
// CHECK-MESSAGES: :[[@LINE-1]]:26: warning: both sides of overloaded operator are equivalent
// CHECK-MESSAGES: :[[@LINE-1]]:26: warning: both sides of operator are equivalent
}
void TestTemplate() { TemplateCheck<MyClass, MyClass>(); }
@ -281,9 +301,46 @@ int TestBitwise(int X, int Y) {
return 0;
}
// Overloaded operators that compare an instance of a struct and an integer
// constant.
struct S {
S() { x = 1; }
int x;
// Overloaded comparison operators without any possible side effect.
bool operator==(const int &i) const { return x == i; } // not modifying
bool operator!=(int i) const { return x != i; } // not modifying
bool operator>(const int &i) const { return x > i; } // not modifying
bool operator<(int i) const { return x < i; } // not modifying
};
bool operator<=(const S &s, int i) { return s.x <= i; } // not modifying
bool operator>=(const S &s, const int &i) { return s.x >= i; } // not modifying
struct S2 {
S2() { x = 1; }
int x;
// Overloaded comparison operators that are able to modify their params.
bool operator==(const int &i) {
this->x++;
return x == i;
}
bool operator!=(int i) { return x != i; }
bool operator>(const int &i) { return x > i; }
bool operator<(int i) {
this->x--;
return x < i;
}
};
bool operator>=(S2 &s, const int &i) { return s.x >= i; }
bool operator<=(S2 &s, int i) {
s.x++;
return s.x <= i;
}
int TestLogical(int X, int Y){
#define CONFIG 0
if (CONFIG && X) return 1; // OK, consts from macros are considered intentional
if (CONFIG && X) return 1;
#undef CONFIG
#define CONFIG 1
if (CONFIG || X) return 1;
@ -331,6 +388,24 @@ int TestLogical(int X, int Y){
if (!X && Y) return 1;
if (!X && Y == 0) return 1;
if (X == 10 && Y != 10) return 1;
// Test for overloaded operators with constant params.
S s1;
if (s1 == 1 && s1 == 1) return true;
// CHECK-MESSAGES: :[[@LINE-1]]:15: warning: equivalent expression on both sides of logical operator
if (s1 == 1 || s1 != 1) return true;
// CHECK-MESSAGES: :[[@LINE-1]]:15: warning: logical expression is always true
if (s1 > 1 && s1 < 1) return true;
// CHECK-MESSAGES: :[[@LINE-1]]:14: warning: logical expression is always false
if (s1 >= 1 || s1 <= 1) return true;
// CHECK-MESSAGES: :[[@LINE-1]]:15: warning: logical expression is always true
// Test for overloaded operators that may modify their params.
S2 s2;
if (s2 == 1 || s2 != 1) return true;
if (s2 == 1 || s2 == 1) return true;
if (s2 > 1 && s2 < 1) return true;
if (s2 >= 1 || s2 <= 1) return true;
}
int TestRelational(int X, int Y) {