SignedCharMisuseCheck.cpp
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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 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", "")) {}
void SignedCharMisuseCheck::storeOptions(ClangTidyOptions::OptionMap &Opts) {
Options.store(Opts, "CharTypdefsToIgnore", CharTypdefsToIgnoreList);
}
void SignedCharMisuseCheck::registerMatchers(MatchFinder *Finder) {
// 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))));
const auto SignedCharType = expr(hasType(qualType(
allOf(isAnyCharacter(), isSignedInteger(), unless(IntTypedef)))));
const auto IntegerType = qualType(allOf(isInteger(), unless(isAnyCharacter()),
unless(booleanType())))
.bind("integerType");
// We are interested in signed char -> integer conversion.
const auto ImplicitCastExpr =
implicitCastExpr(hasSourceExpression(SignedCharType),
hasImplicitDestinationType(IntegerType))
.bind("castExpression");
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 an assignment/declaration.
const auto CastExpr = expr(anyOf(ImplicitCastExpr, CStyleCastExpr,
StaticCastExpr, FunctionalCastExpr));
// Catch assignments with the suspicious type conversion.
const auto AssignmentOperatorExpr = expr(binaryOperator(
hasOperatorName("="), hasLHS(hasType(IntegerType)), hasRHS(CastExpr)));
Finder->addMatcher(AssignmentOperatorExpr, this);
// Catch declarations with the suspicious type conversion.
const auto Declaration =
varDecl(isDefinition(), hasType(IntegerType), hasInitializer(CastExpr));
Finder->addMatcher(Declaration, this);
}
void SignedCharMisuseCheck::check(const MatchFinder::MatchResult &Result) {
const auto *CastExpression =
Result.Nodes.getNodeAs<ImplicitCastExpr>("castExpression");
const auto *IntegerType = Result.Nodes.getNodeAs<QualType>("integerType");
assert(CastExpression);
assert(IntegerType);
// Ignore the match if we know that the value is not negative.
// The potential misinterpretation happens for negative values only.
Expr::EvalResult EVResult;
if (!CastExpression->isValueDependent() &&
CastExpression->getSubExpr()->EvaluateAsInt(EVResult, *Result.Context)) {
llvm::APSInt Value1 = EVResult.Val.getInt();
if (Value1.isNonNegative())
return;
}
diag(CastExpression->getBeginLoc(),
"'signed char' to %0 conversion; "
"consider casting to 'unsigned char' first.")
<< *IntegerType;
}
} // namespace bugprone
} // namespace tidy
} // namespace clang