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//===--- SignedCharMisuseCheck.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 "SignedCharMisuseCheck.h"
#include "../utils/OptionsUtils.h"
#include "clang/AST/ASTContext.h"
#include "clang/ASTMatchers/ASTMatchFinder.h"
using namespace clang::ast_matchers;
using namespace clang::ast_matchers::internal;
namespace clang {
namespace tidy {
namespace bugprone {
static constexpr int UnsignedASCIIUpperBound = 127;
static Matcher<TypedefDecl> hasAnyListedName(const std::string &Names) {
const std::vector<std::string> NameList =
utils::options::parseStringList(Names);
return hasAnyName(std::vector<StringRef>(NameList.begin(), NameList.end()));
}
SignedCharMisuseCheck::SignedCharMisuseCheck(StringRef Name,
ClangTidyContext *Context)
: ClangTidyCheck(Name, Context),
CharTypdefsToIgnoreList(Options.get("CharTypdefsToIgnore", "")),
DiagnoseSignedUnsignedCharComparisons(
Options.get("DiagnoseSignedUnsignedCharComparisons", true)) {}
void SignedCharMisuseCheck::storeOptions(ClangTidyOptions::OptionMap &Opts) {
Options.store(Opts, "CharTypdefsToIgnore", CharTypdefsToIgnoreList);
Options.store(Opts, "DiagnoseSignedUnsignedCharComparisons",
DiagnoseSignedUnsignedCharComparisons);
}
// Create a matcher for char -> integer cast.
BindableMatcher<clang::Stmt> SignedCharMisuseCheck::charCastExpression(
bool IsSigned, const Matcher<clang::QualType> &IntegerType,
const std::string &CastBindName) const {
// We can ignore typedefs which are some kind of integer types
// (e.g. typedef char sal_Int8). In this case, we don't need to
// worry about the misinterpretation of char values.
const auto IntTypedef = qualType(
hasDeclaration(typedefDecl(hasAnyListedName(CharTypdefsToIgnoreList))));
auto CharTypeExpr = expr();
if (IsSigned) {
CharTypeExpr = expr(hasType(
qualType(isAnyCharacter(), isSignedInteger(), unless(IntTypedef))));
} else {
CharTypeExpr = expr(hasType(qualType(
isAnyCharacter(), unless(isSignedInteger()), unless(IntTypedef))));
}
const auto ImplicitCastExpr =
implicitCastExpr(hasSourceExpression(CharTypeExpr),
hasImplicitDestinationType(IntegerType))
.bind(CastBindName);
const auto CStyleCastExpr = cStyleCastExpr(has(ImplicitCastExpr));
const auto StaticCastExpr = cxxStaticCastExpr(has(ImplicitCastExpr));
const auto FunctionalCastExpr = cxxFunctionalCastExpr(has(ImplicitCastExpr));
// We catch any type of casts to an integer. We need to have these cast
// expressions explicitly to catch only those casts which are direct children
// of the checked expressions. (e.g. assignment, declaration).
return traverse(TK_AsIs, expr(anyOf(ImplicitCastExpr, CStyleCastExpr,
StaticCastExpr, FunctionalCastExpr)));
}
void SignedCharMisuseCheck::registerMatchers(MatchFinder *Finder) {
const auto IntegerType =
qualType(isInteger(), unless(isAnyCharacter()), unless(booleanType()))
.bind("integerType");
const auto SignedCharCastExpr =
charCastExpression(true, IntegerType, "signedCastExpression");
const auto UnSignedCharCastExpr =
charCastExpression(false, IntegerType, "unsignedCastExpression");
// Catch assignments with signed char -> integer conversion.
const auto AssignmentOperatorExpr =
expr(binaryOperator(hasOperatorName("="), hasLHS(hasType(IntegerType)),
hasRHS(SignedCharCastExpr)));
Finder->addMatcher(AssignmentOperatorExpr, this);
// Catch declarations with signed char -> integer conversion.
const auto Declaration = varDecl(isDefinition(), hasType(IntegerType),
hasInitializer(SignedCharCastExpr));
Finder->addMatcher(Declaration, this);
if (DiagnoseSignedUnsignedCharComparisons) {
// Catch signed char/unsigned char comparison.
const auto CompareOperator =
expr(binaryOperator(hasAnyOperatorName("==", "!="),
anyOf(allOf(hasLHS(SignedCharCastExpr),
hasRHS(UnSignedCharCastExpr)),
allOf(hasLHS(UnSignedCharCastExpr),
hasRHS(SignedCharCastExpr)))))
.bind("comparison");
Finder->addMatcher(CompareOperator, this);
}
// Catch array subscripts with signed char -> integer conversion.
// Matcher for C arrays.
const auto CArraySubscript =
arraySubscriptExpr(hasIndex(SignedCharCastExpr)).bind("arraySubscript");
Finder->addMatcher(CArraySubscript, this);
// Matcher for std arrays.
const auto STDArraySubscript =
cxxOperatorCallExpr(
hasOverloadedOperatorName("[]"),
hasArgument(0, hasType(cxxRecordDecl(hasName("::std::array")))),
hasArgument(1, SignedCharCastExpr))
.bind("arraySubscript");
Finder->addMatcher(STDArraySubscript, this);
}
void SignedCharMisuseCheck::check(const MatchFinder::MatchResult &Result) {
const auto *SignedCastExpression =
Result.Nodes.getNodeAs<ImplicitCastExpr>("signedCastExpression");
const auto *IntegerType = Result.Nodes.getNodeAs<QualType>("integerType");
assert(SignedCastExpression);
assert(IntegerType);
// Ignore the match if we know that the signed char's value is not negative.
// The potential misinterpretation happens for negative values only.
Expr::EvalResult EVResult;
if (!SignedCastExpression->isValueDependent() &&
SignedCastExpression->getSubExpr()->EvaluateAsInt(EVResult,
*Result.Context)) {
llvm::APSInt Value = EVResult.Val.getInt();
if (Value.isNonNegative())
return;
}
if (const auto *Comparison = Result.Nodes.getNodeAs<Expr>("comparison")) {
const auto *UnSignedCastExpression =
Result.Nodes.getNodeAs<ImplicitCastExpr>("unsignedCastExpression");
// We can ignore the ASCII value range also for unsigned char.
Expr::EvalResult EVResult;
if (!UnSignedCastExpression->isValueDependent() &&
UnSignedCastExpression->getSubExpr()->EvaluateAsInt(EVResult,
*Result.Context)) {
llvm::APSInt Value = EVResult.Val.getInt();
if (Value <= UnsignedASCIIUpperBound)
return;
}
diag(Comparison->getBeginLoc(),
"comparison between 'signed char' and 'unsigned char'");
} else if (Result.Nodes.getNodeAs<Expr>("arraySubscript")) {
diag(SignedCastExpression->getBeginLoc(),
"'signed char' to %0 conversion in array subscript; "
"consider casting to 'unsigned char' first.")
<< *IntegerType;
} else {
diag(SignedCastExpression->getBeginLoc(),
"'signed char' to %0 conversion; "
"consider casting to 'unsigned char' first.")
<< *IntegerType;
}
}
} // namespace bugprone
} // namespace tidy
} // namespace clang
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