1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259
|
//===--- AvoidCStyleCastsCheck.cpp - clang-tidy -----------------*- C++ -*-===//
//
// 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 "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);
Finder->addMatcher(
cxxFunctionalCastExpr(unless(hasDescendant(cxxConstructExpr())),
unless(hasDescendant(initListExpr())))
.bind("cast"),
this);
}
static bool needsConstCast(QualType SourceType, QualType DestType) {
while ((SourceType->isPointerType() && DestType->isPointerType()) ||
(SourceType->isReferenceType() && DestType->isReferenceType())) {
SourceType = SourceType->getPointeeType();
DestType = DestType->getPointeeType();
if (SourceType.isConstQualified() && !DestType.isConstQualified()) {
return (SourceType->isPointerType() == DestType->isPointerType()) &&
(SourceType->isReferenceType() == DestType->isReferenceType());
}
}
return false;
}
static bool pointedUnqualifiedTypesAreEqual(QualType T1, QualType T2) {
while ((T1->isPointerType() && T2->isPointerType()) ||
(T1->isReferenceType() && T2->isReferenceType())) {
T1 = T1->getPointeeType();
T2 = T2->getPointeeType();
}
return T1.getUnqualifiedType() == T2.getUnqualifiedType();
}
static clang::CharSourceRange getReplaceRange(const ExplicitCastExpr *Expr) {
if (const auto *CastExpr = dyn_cast<CStyleCastExpr>(Expr)) {
return CharSourceRange::getCharRange(
CastExpr->getLParenLoc(),
CastExpr->getSubExprAsWritten()->getBeginLoc());
} else if (const auto *CastExpr = dyn_cast<CXXFunctionalCastExpr>(Expr)) {
return CharSourceRange::getCharRange(CastExpr->getBeginLoc(),
CastExpr->getLParenLoc());
} else
llvm_unreachable("Unsupported CastExpr");
}
static StringRef getDestTypeString(const SourceManager &SM,
const LangOptions &LangOpts,
const ExplicitCastExpr *Expr) {
SourceLocation BeginLoc;
SourceLocation EndLoc;
if (const auto *CastExpr = dyn_cast<CStyleCastExpr>(Expr)) {
BeginLoc = CastExpr->getLParenLoc().getLocWithOffset(1);
EndLoc = CastExpr->getRParenLoc().getLocWithOffset(-1);
} else if (const auto *CastExpr = dyn_cast<CXXFunctionalCastExpr>(Expr)) {
BeginLoc = CastExpr->getBeginLoc();
EndLoc = CastExpr->getLParenLoc().getLocWithOffset(-1);
} else
llvm_unreachable("Unsupported CastExpr");
return Lexer::getSourceText(CharSourceRange::getTokenRange(BeginLoc, EndLoc),
SM, LangOpts);
}
void AvoidCStyleCastsCheck::check(const MatchFinder::MatchResult &Result) {
const auto *CastExpr = Result.Nodes.getNodeAs<ExplicitCastExpr>("cast");
// Ignore casts in macros.
if (CastExpr->getExprLoc().isMacroID())
return;
// Casting to void is an idiomatic way to mute "unused variable" and similar
// warnings.
if (CastExpr->getCastKind() == CK_ToVoid)
return;
auto IsFunction = [](QualType T) {
T = T.getCanonicalType().getNonReferenceType();
return T->isFunctionType() || T->isFunctionPointerType() ||
T->isMemberFunctionPointerType();
};
const QualType DestTypeAsWritten =
CastExpr->getTypeAsWritten().getUnqualifiedType();
const QualType SourceTypeAsWritten =
CastExpr->getSubExprAsWritten()->getType().getUnqualifiedType();
const QualType SourceType = SourceTypeAsWritten.getCanonicalType();
const QualType DestType = DestTypeAsWritten.getCanonicalType();
CharSourceRange ReplaceRange = getReplaceRange(CastExpr);
bool FnToFnCast =
IsFunction(SourceTypeAsWritten) && IsFunction(DestTypeAsWritten);
const bool ConstructorCast = !CastExpr->getTypeAsWritten().hasQualifiers() &&
DestTypeAsWritten->isRecordType() &&
!DestTypeAsWritten->isElaboratedTypeSpecifier();
if (CastExpr->getCastKind() == CK_NoOp && !FnToFnCast) {
// Function pointer/reference casts may be needed to resolve ambiguities in
// case of overloaded functions, so detection of redundant casts is trickier
// in this case. Don't emit "redundant cast" warnings for function
// pointer/reference types.
if (SourceTypeAsWritten == DestTypeAsWritten) {
diag(CastExpr->getBeginLoc(), "redundant cast to the same type")
<< FixItHint::CreateRemoval(ReplaceRange);
return;
}
}
// The rest of this check is only relevant to C++.
// We also disable it for Objective-C++.
if (!getLangOpts().CPlusPlus || getLangOpts().ObjC)
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;
SourceManager &SM = *Result.SourceManager;
// Ignore code in .c files #included in other files (which shouldn't be done,
// but people still do this for test and other purposes).
if (SM.getFilename(SM.getSpellingLoc(CastExpr->getBeginLoc())).endswith(".c"))
return;
// Leave type spelling exactly as it was (unlike
// getTypeAsWritten().getAsString() which would spell enum types 'enum X').
StringRef DestTypeString = getDestTypeString(SM, getLangOpts(), CastExpr);
auto Diag =
diag(CastExpr->getBeginLoc(), "C-style casts are discouraged; use %0");
auto ReplaceWithCast = [&](std::string CastText) {
const Expr *SubExpr = CastExpr->getSubExprAsWritten()->IgnoreImpCasts();
if (!isa<ParenExpr>(SubExpr) && !isa<CXXFunctionalCastExpr>(CastExpr)) {
CastText.push_back('(');
Diag << FixItHint::CreateInsertion(
Lexer::getLocForEndOfToken(SubExpr->getEndLoc(), 0, SM,
getLangOpts()),
")");
}
Diag << FixItHint::CreateReplacement(ReplaceRange, CastText);
};
auto ReplaceWithNamedCast = [&](StringRef CastType) {
Diag << CastType;
ReplaceWithCast((CastType + "<" + DestTypeString + ">").str());
};
auto ReplaceWithConstructorCall = [&]() {
Diag << "constructor call syntax";
// FIXME: Validate DestTypeString, maybe.
ReplaceWithCast(DestTypeString.str());
};
// Suggest appropriate C++ cast. See [expr.cast] for cast notation semantics.
switch (CastExpr->getCastKind()) {
case CK_FunctionToPointerDecay:
ReplaceWithNamedCast("static_cast");
return;
case CK_ConstructorConversion:
if (ConstructorCast) {
ReplaceWithConstructorCall();
} else {
ReplaceWithNamedCast("static_cast");
}
return;
case CK_NoOp:
if (FnToFnCast) {
ReplaceWithNamedCast("static_cast");
return;
}
if (SourceType == DestType) {
Diag << "static_cast (if needed, the cast may be redundant)";
ReplaceWithCast(("static_cast<" + DestTypeString + ">").str());
return;
}
if (needsConstCast(SourceType, DestType) &&
pointedUnqualifiedTypesAreEqual(SourceType, DestType)) {
ReplaceWithNamedCast("const_cast");
return;
}
if (ConstructorCast) {
ReplaceWithConstructorCall();
return;
}
if (DestType->isReferenceType()) {
QualType Dest = DestType.getNonReferenceType();
QualType Source = SourceType.getNonReferenceType();
if (Source == Dest.withConst() ||
SourceType.getNonReferenceType() == DestType.getNonReferenceType()) {
ReplaceWithNamedCast("const_cast");
return;
}
break;
}
LLVM_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())) {
ReplaceWithNamedCast("static_cast");
return;
}
break;
case CK_BitCast:
// FIXME: Suggest const_cast<...>(reinterpret_cast<...>(...)) replacement.
if (!needsConstCast(SourceType, DestType)) {
if (SourceType->isVoidPointerType())
ReplaceWithNamedCast("static_cast");
else
ReplaceWithNamedCast("reinterpret_cast");
return;
}
break;
default:
break;
}
Diag << "static_cast/const_cast/reinterpret_cast";
}
} // namespace readability
} // namespace google
} // namespace tidy
} // namespace clang
|