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//===--- AvoidCStyleCastsCheck.cpp - clang-tidy -----------------*- C++ -*-===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
#include "AvoidCStyleCastsCheck.h"
#include "clang/AST/ASTContext.h"
#include "clang/ASTMatchers/ASTMatchFinder.h"
#include "clang/ASTMatchers/ASTMatchers.h"
#include "clang/Lex/Lexer.h"
using namespace clang::ast_matchers;
namespace clang {
namespace tidy {
namespace google {
namespace readability {
void
AvoidCStyleCastsCheck::registerMatchers(ast_matchers::MatchFinder *Finder) {
Finder->addMatcher(
cStyleCastExpr(
// Filter out (EnumType)IntegerLiteral construct, which is generated
// for non-type template arguments of enum types.
// FIXME: Remove this once this is fixed in the AST.
unless(hasParent(substNonTypeTemplateParmExpr())),
// Avoid matches in template instantiations.
unless(isInTemplateInstantiation())).bind("cast"),
this);
}
static bool needsConstCast(QualType SourceType, QualType DestType) {
SourceType = SourceType.getNonReferenceType();
DestType = DestType.getNonReferenceType();
while (SourceType->isPointerType() && DestType->isPointerType()) {
SourceType = SourceType->getPointeeType();
DestType = DestType->getPointeeType();
if (SourceType.isConstQualified() && !DestType.isConstQualified())
return true;
}
return false;
}
static bool pointedTypesAreEqual(QualType SourceType, QualType DestType) {
SourceType = SourceType.getNonReferenceType();
DestType = DestType.getNonReferenceType();
while (SourceType->isPointerType() && DestType->isPointerType()) {
SourceType = SourceType->getPointeeType();
DestType = DestType->getPointeeType();
}
return SourceType.getUnqualifiedType() == DestType.getUnqualifiedType();
}
void AvoidCStyleCastsCheck::check(const MatchFinder::MatchResult &Result) {
const auto *CastExpr = Result.Nodes.getNodeAs<CStyleCastExpr>("cast");
auto ParenRange = CharSourceRange::getTokenRange(CastExpr->getLParenLoc(),
CastExpr->getRParenLoc());
// Ignore casts in macros.
if (ParenRange.getBegin().isMacroID() || ParenRange.getEnd().isMacroID())
return;
// Casting to void is an idiomatic way to mute "unused variable" and similar
// warnings.
if (CastExpr->getTypeAsWritten()->isVoidType())
return;
QualType SourceType = CastExpr->getSubExprAsWritten()->getType();
QualType DestType = CastExpr->getTypeAsWritten();
if (SourceType == DestType) {
diag(CastExpr->getLocStart(), "redundant cast to the same type")
<< FixItHint::CreateRemoval(ParenRange);
return;
}
SourceType = SourceType.getCanonicalType();
DestType = DestType.getCanonicalType();
if (SourceType == DestType) {
diag(CastExpr->getLocStart(),
"possibly redundant cast between typedefs of the same type");
return;
}
// The rest of this check is only relevant to C++.
if (!Result.Context->getLangOpts().CPlusPlus)
return;
// Ignore code inside extern "C" {} blocks.
if (!match(expr(hasAncestor(linkageSpecDecl())), *CastExpr, *Result.Context)
.empty())
return;
// Ignore code in .c files and headers included from them, even if they are
// compiled as C++.
if (getCurrentMainFile().endswith(".c"))
return;
// Ignore code in .c files #included in other files (which shouldn't be done,
// but people still do this for test and other purposes).
SourceManager &SM = *Result.SourceManager;
if (SM.getFilename(SM.getSpellingLoc(CastExpr->getLocStart())).endswith(".c"))
return;
// Leave type spelling exactly as it was (unlike
// getTypeAsWritten().getAsString() which would spell enum types 'enum X').
StringRef DestTypeString =
Lexer::getSourceText(CharSourceRange::getTokenRange(
CastExpr->getLParenLoc().getLocWithOffset(1),
CastExpr->getRParenLoc().getLocWithOffset(-1)),
SM, Result.Context->getLangOpts());
auto diag_builder =
diag(CastExpr->getLocStart(), "C-style casts are discouraged. %0");
auto ReplaceWithCast = [&](StringRef CastType) {
diag_builder << ("Use " + CastType).str();
const Expr *SubExpr = CastExpr->getSubExprAsWritten()->IgnoreImpCasts();
std::string CastText = (CastType + "<" + DestTypeString + ">").str();
if (!isa<ParenExpr>(SubExpr)) {
CastText.push_back('(');
diag_builder << FixItHint::CreateInsertion(
Lexer::getLocForEndOfToken(SubExpr->getLocEnd(), 0, SM,
Result.Context->getLangOpts()),
")");
}
diag_builder << FixItHint::CreateReplacement(ParenRange, CastText);
};
// Suggest appropriate C++ cast. See [expr.cast] for cast notation semantics.
switch (CastExpr->getCastKind()) {
case CK_NoOp:
if (needsConstCast(SourceType, DestType) &&
pointedTypesAreEqual(SourceType, DestType)) {
ReplaceWithCast("const_cast");
return;
}
if (DestType->isReferenceType() &&
(SourceType.getNonReferenceType() ==
DestType.getNonReferenceType().withConst() ||
SourceType.getNonReferenceType() == DestType.getNonReferenceType())) {
ReplaceWithCast("const_cast");
return;
}
// FALLTHROUGH
case clang::CK_IntegralCast:
// Convert integral and no-op casts between builtin types and enums to
// static_cast. A cast from enum to integer may be unnecessary, but it's
// still retained.
if ((SourceType->isBuiltinType() || SourceType->isEnumeralType()) &&
(DestType->isBuiltinType() || DestType->isEnumeralType())) {
ReplaceWithCast("static_cast");
return;
}
break;
case CK_BitCast:
// FIXME: Suggest const_cast<...>(reinterpret_cast<...>(...)) replacement.
if (!needsConstCast(SourceType, DestType)) {
ReplaceWithCast("reinterpret_cast");
return;
}
break;
default:
break;
}
diag_builder << "Use static_cast/const_cast/reinterpret_cast";
}
} // namespace readability
} // namespace google
} // namespace tidy
} // namespace clang
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