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//===--- ConfusableIdentifierCheck.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 "ConfusableIdentifierCheck.h"
#include "clang/Frontend/CompilerInstance.h"
#include "clang/Lex/Preprocessor.h"
#include "llvm/Support/ConvertUTF.h"
namespace {
// Preprocessed version of
// https://www.unicode.org/Public/security/latest/confusables.txt
//
// This contains a sorted array of { UTF32 codepoint; UTF32 values[N];}
#include "Confusables.inc"
} // namespace
namespace clang::tidy::misc {
ConfusableIdentifierCheck::ConfusableIdentifierCheck(StringRef Name,
ClangTidyContext *Context)
: ClangTidyCheck(Name, Context) {}
ConfusableIdentifierCheck::~ConfusableIdentifierCheck() = default;
// Build a skeleton out of the Original identifier, inspired by the algorithm
// described in http://www.unicode.org/reports/tr39/#def-skeleton
//
// FIXME: TR39 mandates:
//
// For an input string X, define skeleton(X) to be the following transformation
// on the string:
//
// 1. Convert X to NFD format, as described in [UAX15].
// 2. Concatenate the prototypes for each character in X according to the
// specified data, producing a string of exemplar characters.
// 3. Reapply NFD.
//
// We're skipping 1. and 3. for the sake of simplicity, but this can lead to
// false positive.
std::string ConfusableIdentifierCheck::skeleton(StringRef Name) {
using namespace llvm;
std::string SName = Name.str();
std::string Skeleton;
Skeleton.reserve(1 + Name.size());
const char *Curr = SName.c_str();
const char *End = Curr + SName.size();
while (Curr < End) {
const char *Prev = Curr;
UTF32 CodePoint;
ConversionResult Result = convertUTF8Sequence(
reinterpret_cast<const UTF8 **>(&Curr),
reinterpret_cast<const UTF8 *>(End), &CodePoint, strictConversion);
if (Result != conversionOK) {
errs() << "Unicode conversion issue\n";
break;
}
StringRef Key(Prev, Curr - Prev);
auto Where = llvm::lower_bound(ConfusableEntries, CodePoint,
[](decltype(ConfusableEntries[0]) x,
UTF32 y) { return x.codepoint < y; });
if (Where == std::end(ConfusableEntries) || CodePoint != Where->codepoint) {
Skeleton.append(Prev, Curr);
} else {
UTF8 Buffer[32];
UTF8 *BufferStart = std::begin(Buffer);
UTF8 *IBuffer = BufferStart;
const UTF32 *ValuesStart = std::begin(Where->values);
const UTF32 *ValuesEnd = llvm::find(Where->values, '\0');
if (ConvertUTF32toUTF8(&ValuesStart, ValuesEnd, &IBuffer,
std::end(Buffer),
strictConversion) != conversionOK) {
errs() << "Unicode conversion issue\n";
break;
}
Skeleton.append((char *)BufferStart, (char *)IBuffer);
}
}
return Skeleton;
}
static bool mayShadowImpl(const NamedDecl *ND0, const NamedDecl *ND1) {
const DeclContext *DC0 = ND0->getDeclContext()->getPrimaryContext();
const DeclContext *DC1 = ND1->getDeclContext()->getPrimaryContext();
if (isa<TemplateTypeParmDecl>(ND0) || isa<TemplateTypeParmDecl>(ND0))
return true;
while (DC0->isTransparentContext())
DC0 = DC0->getParent();
while (DC1->isTransparentContext())
DC1 = DC1->getParent();
if (DC0->Equals(DC1))
return true;
return false;
}
static bool isMemberOf(const NamedDecl *ND, const CXXRecordDecl *RD) {
const DeclContext *NDParent = ND->getDeclContext();
if (!NDParent || !isa<CXXRecordDecl>(NDParent))
return false;
if (NDParent == RD)
return true;
return !RD->forallBases(
[NDParent](const CXXRecordDecl *Base) { return NDParent != Base; });
}
static bool mayShadow(const NamedDecl *ND0, const NamedDecl *ND1) {
const DeclContext *DC0 = ND0->getDeclContext()->getPrimaryContext();
const DeclContext *DC1 = ND1->getDeclContext()->getPrimaryContext();
if (const CXXRecordDecl *RD0 = dyn_cast<CXXRecordDecl>(DC0)) {
RD0 = RD0->getDefinition();
if (RD0 && ND1->getAccess() != AS_private && isMemberOf(ND1, RD0))
return true;
}
if (const CXXRecordDecl *RD1 = dyn_cast<CXXRecordDecl>(DC1)) {
RD1 = RD1->getDefinition();
if (RD1 && ND0->getAccess() != AS_private && isMemberOf(ND0, RD1))
return true;
}
if (DC0->Encloses(DC1))
return mayShadowImpl(ND0, ND1);
if (DC1->Encloses(DC0))
return mayShadowImpl(ND1, ND0);
return false;
}
void ConfusableIdentifierCheck::check(
const ast_matchers::MatchFinder::MatchResult &Result) {
if (const auto *ND = Result.Nodes.getNodeAs<NamedDecl>("nameddecl")) {
if (IdentifierInfo *NDII = ND->getIdentifier()) {
StringRef NDName = NDII->getName();
llvm::SmallVector<const NamedDecl *> &Mapped = Mapper[skeleton(NDName)];
for (const NamedDecl *OND : Mapped) {
const IdentifierInfo *ONDII = OND->getIdentifier();
if (mayShadow(ND, OND)) {
StringRef ONDName = ONDII->getName();
if (ONDName != NDName) {
diag(ND->getLocation(), "%0 is confusable with %1") << ND << OND;
diag(OND->getLocation(), "other declaration found here",
DiagnosticIDs::Note);
}
}
}
Mapped.push_back(ND);
}
}
}
void ConfusableIdentifierCheck::registerMatchers(
ast_matchers::MatchFinder *Finder) {
Finder->addMatcher(ast_matchers::namedDecl().bind("nameddecl"), this);
}
} // namespace clang::tidy::misc
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