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//===--- SizeofExpressionCheck.cpp - clang-tidy----------------------------===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
#include "SizeofExpressionCheck.h"
#include "../utils/Matchers.h"
#include "clang/AST/ASTContext.h"
#include "clang/ASTMatchers/ASTMatchFinder.h"
using namespace clang::ast_matchers;
namespace clang {
namespace tidy {
namespace misc {
namespace {
AST_MATCHER_P(IntegerLiteral, isBiggerThan, unsigned, N) {
return Node.getValue().getZExtValue() > N;
}
AST_MATCHER_P2(Expr, hasSizeOfDescendant, int, Depth,
ast_matchers::internal::Matcher<Expr>, InnerMatcher) {
if (Depth < 0)
return false;
const Expr *E = Node.IgnoreParenImpCasts();
if (InnerMatcher.matches(*E, Finder, Builder))
return true;
if (const auto *CE = dyn_cast<CastExpr>(E)) {
const auto M = hasSizeOfDescendant(Depth - 1, InnerMatcher);
return M.matches(*CE->getSubExpr(), Finder, Builder);
} else if (const auto *UE = dyn_cast<UnaryOperator>(E)) {
const auto M = hasSizeOfDescendant(Depth - 1, InnerMatcher);
return M.matches(*UE->getSubExpr(), Finder, Builder);
} else if (const auto *BE = dyn_cast<BinaryOperator>(E)) {
const auto LHS = hasSizeOfDescendant(Depth - 1, InnerMatcher);
const auto RHS = hasSizeOfDescendant(Depth - 1, InnerMatcher);
return LHS.matches(*BE->getLHS(), Finder, Builder) ||
RHS.matches(*BE->getRHS(), Finder, Builder);
}
return false;
}
CharUnits getSizeOfType(const ASTContext &Ctx, const Type *Ty) {
if (!Ty || Ty->isIncompleteType() || Ty->isDependentType() ||
isa<DependentSizedArrayType>(Ty) || !Ty->isConstantSizeType())
return CharUnits::Zero();
return Ctx.getTypeSizeInChars(Ty);
}
} // namespace
SizeofExpressionCheck::SizeofExpressionCheck(StringRef Name,
ClangTidyContext *Context)
: ClangTidyCheck(Name, Context),
WarnOnSizeOfConstant(Options.get("WarnOnSizeOfConstant", 1) != 0),
WarnOnSizeOfThis(Options.get("WarnOnSizeOfThis", 1) != 0),
WarnOnSizeOfCompareToConstant(
Options.get("WarnOnSizeOfCompareToConstant", 1) != 0) {}
void SizeofExpressionCheck::storeOptions(ClangTidyOptions::OptionMap &Opts) {
Options.store(Opts, "WarnOnSizeOfConstant", WarnOnSizeOfConstant);
Options.store(Opts, "WarnOnSizeOfThis", WarnOnSizeOfThis);
Options.store(Opts, "WarnOnSizeOfCompareToConstant",
WarnOnSizeOfCompareToConstant);
}
void SizeofExpressionCheck::registerMatchers(MatchFinder *Finder) {
const auto IntegerExpr = ignoringParenImpCasts(integerLiteral());
const auto ConstantExpr = expr(ignoringParenImpCasts(
anyOf(integerLiteral(), unaryOperator(hasUnaryOperand(IntegerExpr)),
binaryOperator(hasLHS(IntegerExpr), hasRHS(IntegerExpr)))));
const auto SizeOfExpr =
expr(anyOf(sizeOfExpr(has(type())), sizeOfExpr(has(expr()))));
const auto SizeOfZero = expr(
sizeOfExpr(has(ignoringParenImpCasts(expr(integerLiteral(equals(0)))))));
// Detect expression like: sizeof(ARRAYLEN);
// Note: The expression 'sizeof(sizeof(0))' is a portable trick used to know
// the sizeof size_t.
if (WarnOnSizeOfConstant) {
Finder->addMatcher(
expr(sizeOfExpr(has(ignoringParenImpCasts(ConstantExpr))),
unless(SizeOfZero))
.bind("sizeof-constant"),
this);
}
// Detect expression like: sizeof(this);
if (WarnOnSizeOfThis) {
Finder->addMatcher(
expr(sizeOfExpr(has(ignoringParenImpCasts(expr(cxxThisExpr())))))
.bind("sizeof-this"),
this);
}
// Detect sizeof(kPtr) where kPtr is 'const char* kPtr = "abc"';
const auto CharPtrType = pointerType(pointee(isAnyCharacter()));
const auto ConstStrLiteralDecl =
varDecl(isDefinition(), hasType(qualType(hasCanonicalType(CharPtrType))),
hasInitializer(ignoringParenImpCasts(stringLiteral())));
Finder->addMatcher(expr(sizeOfExpr(has(ignoringParenImpCasts(expr(
hasType(qualType(hasCanonicalType(CharPtrType))),
ignoringParenImpCasts(declRefExpr(
hasDeclaration(ConstStrLiteralDecl))))))))
.bind("sizeof-charp"),
this);
// Detect sizeof(ptr) where ptr points to an aggregate (i.e. sizeof(&S)).
const auto ArrayExpr = expr(ignoringParenImpCasts(
expr(hasType(qualType(hasCanonicalType(arrayType()))))));
const auto ArrayCastExpr = expr(anyOf(
unaryOperator(hasUnaryOperand(ArrayExpr), unless(hasOperatorName("*"))),
binaryOperator(hasEitherOperand(ArrayExpr)),
castExpr(hasSourceExpression(ArrayExpr))));
const auto PointerToArrayExpr = expr(ignoringParenImpCasts(expr(
hasType(qualType(hasCanonicalType(pointerType(pointee(arrayType()))))))));
const auto StructAddrOfExpr =
unaryOperator(hasOperatorName("&"),
hasUnaryOperand(ignoringParenImpCasts(expr(
hasType(qualType(hasCanonicalType(recordType())))))));
Finder->addMatcher(
expr(sizeOfExpr(has(expr(ignoringParenImpCasts(
anyOf(ArrayCastExpr, PointerToArrayExpr, StructAddrOfExpr))))))
.bind("sizeof-pointer-to-aggregate"),
this);
// Detect expression like: sizeof(epxr) <= k for a suspicious constant 'k'.
if (WarnOnSizeOfCompareToConstant) {
Finder->addMatcher(
binaryOperator(matchers::isRelationalOperator(),
hasEitherOperand(ignoringParenImpCasts(SizeOfExpr)),
hasEitherOperand(ignoringParenImpCasts(
anyOf(integerLiteral(equals(0)),
integerLiteral(isBiggerThan(0x80000))))))
.bind("sizeof-compare-constant"),
this);
}
// Detect expression like: sizeof(expr, expr); most likely an error.
Finder->addMatcher(expr(sizeOfExpr(has(expr(ignoringParenImpCasts(
binaryOperator(hasOperatorName(",")))))))
.bind("sizeof-comma-expr"),
this);
// Detect sizeof(...) /sizeof(...));
const auto ElemType =
arrayType(hasElementType(recordType().bind("elem-type")));
const auto ElemPtrType = pointerType(pointee(type().bind("elem-ptr-type")));
const auto NumType = qualType(hasCanonicalType(
type(anyOf(ElemType, ElemPtrType, type())).bind("num-type")));
const auto DenomType = qualType(hasCanonicalType(type().bind("denom-type")));
Finder->addMatcher(
binaryOperator(hasOperatorName("/"),
hasLHS(expr(ignoringParenImpCasts(
anyOf(sizeOfExpr(has(NumType)),
sizeOfExpr(has(expr(hasType(NumType)))))))),
hasRHS(expr(ignoringParenImpCasts(
anyOf(sizeOfExpr(has(DenomType)),
sizeOfExpr(has(expr(hasType(DenomType)))))))))
.bind("sizeof-divide-expr"),
this);
// Detect expression like: sizeof(...) * sizeof(...)); most likely an error.
Finder->addMatcher(binaryOperator(hasOperatorName("*"),
hasLHS(ignoringParenImpCasts(SizeOfExpr)),
hasRHS(ignoringParenImpCasts(SizeOfExpr)))
.bind("sizeof-multiply-sizeof"),
this);
Finder->addMatcher(
binaryOperator(hasOperatorName("*"),
hasEitherOperand(ignoringParenImpCasts(SizeOfExpr)),
hasEitherOperand(ignoringParenImpCasts(binaryOperator(
hasOperatorName("*"),
hasEitherOperand(ignoringParenImpCasts(SizeOfExpr))))))
.bind("sizeof-multiply-sizeof"),
this);
// Detect strange double-sizeof expression like: sizeof(sizeof(...));
// Note: The expression 'sizeof(sizeof(0))' is accepted.
Finder->addMatcher(
expr(sizeOfExpr(has(ignoringParenImpCasts(expr(
hasSizeOfDescendant(8, expr(SizeOfExpr, unless(SizeOfZero))))))))
.bind("sizeof-sizeof-expr"),
this);
}
void SizeofExpressionCheck::check(const MatchFinder::MatchResult &Result) {
const ASTContext &Ctx = *Result.Context;
if (const auto *E = Result.Nodes.getNodeAs<Expr>("sizeof-constant")) {
diag(E->getLocStart(),
"suspicious usage of 'sizeof(K)'; did you mean 'K'?");
} else if (const auto *E = Result.Nodes.getNodeAs<Expr>("sizeof-this")) {
diag(E->getLocStart(),
"suspicious usage of 'sizeof(this)'; did you mean 'sizeof(*this)'");
} else if (const auto *E = Result.Nodes.getNodeAs<Expr>("sizeof-charp")) {
diag(E->getLocStart(),
"suspicious usage of 'sizeof(char*)'; do you mean 'strlen'?");
} else if (const auto *E =
Result.Nodes.getNodeAs<Expr>("sizeof-pointer-to-aggregate")) {
diag(E->getLocStart(),
"suspicious usage of 'sizeof(A*)'; pointer to aggregate");
} else if (const auto *E =
Result.Nodes.getNodeAs<Expr>("sizeof-compare-constant")) {
diag(E->getLocStart(),
"suspicious comparison of 'sizeof(expr)' to a constant");
} else if (const auto *E =
Result.Nodes.getNodeAs<Expr>("sizeof-comma-expr")) {
diag(E->getLocStart(), "suspicious usage of 'sizeof(..., ...)'");
} else if (const auto *E =
Result.Nodes.getNodeAs<Expr>("sizeof-divide-expr")) {
const auto *NumTy = Result.Nodes.getNodeAs<Type>("num-type");
const auto *DenomTy = Result.Nodes.getNodeAs<Type>("denom-type");
const auto *ElementTy = Result.Nodes.getNodeAs<Type>("elem-type");
const auto *PointedTy = Result.Nodes.getNodeAs<Type>("elem-ptr-type");
CharUnits NumeratorSize = getSizeOfType(Ctx, NumTy);
CharUnits DenominatorSize = getSizeOfType(Ctx, DenomTy);
CharUnits ElementSize = getSizeOfType(Ctx, ElementTy);
if (DenominatorSize > CharUnits::Zero() &&
!NumeratorSize.isMultipleOf(DenominatorSize)) {
diag(E->getLocStart(), "suspicious usage of 'sizeof(...)/sizeof(...)';"
" numerator is not a multiple of denominator");
} else if (ElementSize > CharUnits::Zero() &&
DenominatorSize > CharUnits::Zero() &&
ElementSize != DenominatorSize) {
diag(E->getLocStart(), "suspicious usage of 'sizeof(...)/sizeof(...)';"
" numerator is not a multiple of denominator");
} else if (NumTy && DenomTy && NumTy == DenomTy) {
diag(E->getLocStart(),
"suspicious usage of sizeof pointer 'sizeof(T)/sizeof(T)'");
} else if (PointedTy && DenomTy && PointedTy == DenomTy) {
diag(E->getLocStart(),
"suspicious usage of sizeof pointer 'sizeof(T*)/sizeof(T)'");
} else if (NumTy && DenomTy && NumTy->isPointerType() &&
DenomTy->isPointerType()) {
diag(E->getLocStart(),
"suspicious usage of sizeof pointer 'sizeof(P*)/sizeof(Q*)'");
}
} else if (const auto *E =
Result.Nodes.getNodeAs<Expr>("sizeof-sizeof-expr")) {
diag(E->getLocStart(), "suspicious usage of 'sizeof(sizeof(...))'");
} else if (const auto *E =
Result.Nodes.getNodeAs<Expr>("sizeof-multiply-sizeof")) {
diag(E->getLocStart(), "suspicious 'sizeof' by 'sizeof' multiplication");
}
}
} // namespace misc
} // namespace tidy
} // namespace clang
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