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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/ADT/SmallString.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.
static llvm::SmallString<64U> skeleton(StringRef Name) {
using namespace llvm;
SmallString<64U> Skeleton;
Skeleton.reserve(1U + Name.size());
const char *Curr = Name.data();
const char *End = Curr + Name.size();
while (Curr < End) {
const char *Prev = Curr;
UTF32 CodePoint = 0;
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 DeclContext *DC0, const DeclContext *DC1) {
return DC0 && DC0 == DC1;
}
static bool mayShadowImpl(const NamedDecl *ND0, const NamedDecl *ND1) {
return isa<TemplateTypeParmDecl>(ND0) || isa<TemplateTypeParmDecl>(ND1);
}
static bool isMemberOf(const ConfusableIdentifierCheck::ContextInfo *DC0,
const ConfusableIdentifierCheck::ContextInfo *DC1) {
return llvm::is_contained(DC1->Bases, DC0->PrimaryContext);
}
static bool enclosesContext(const ConfusableIdentifierCheck::ContextInfo *DC0,
const ConfusableIdentifierCheck::ContextInfo *DC1) {
if (DC0->PrimaryContext == DC1->PrimaryContext)
return true;
return llvm::is_contained(DC0->PrimaryContexts, DC1->PrimaryContext) ||
llvm::is_contained(DC1->PrimaryContexts, DC0->PrimaryContext);
}
static bool mayShadow(const NamedDecl *ND0,
const ConfusableIdentifierCheck::ContextInfo *DC0,
const NamedDecl *ND1,
const ConfusableIdentifierCheck::ContextInfo *DC1) {
if (!DC0->Bases.empty() && !DC1->Bases.empty()) {
// if any of the declaration is a non-private member of the other
// declaration, it's shadowed by the former
if (ND1->getAccess() != AS_private && isMemberOf(DC1, DC0))
return true;
if (ND0->getAccess() != AS_private && isMemberOf(DC0, DC1))
return true;
}
if (!mayShadowImpl(DC0->NonTransparentContext, DC1->NonTransparentContext) &&
!mayShadowImpl(ND0, ND1))
return false;
return enclosesContext(DC0, DC1);
}
const ConfusableIdentifierCheck::ContextInfo *
ConfusableIdentifierCheck::getContextInfo(const DeclContext *DC) {
const DeclContext *PrimaryContext = DC->getPrimaryContext();
auto [It, Inserted] = ContextInfos.try_emplace(PrimaryContext);
if (!Inserted)
return &It->second;
ContextInfo &Info = It->second;
Info.PrimaryContext = PrimaryContext;
Info.NonTransparentContext = PrimaryContext;
while (Info.NonTransparentContext->isTransparentContext()) {
Info.NonTransparentContext = Info.NonTransparentContext->getParent();
if (!Info.NonTransparentContext)
break;
}
if (Info.NonTransparentContext)
Info.NonTransparentContext =
Info.NonTransparentContext->getPrimaryContext();
while (DC) {
if (!isa<LinkageSpecDecl>(DC) && !isa<ExportDecl>(DC))
Info.PrimaryContexts.push_back(DC->getPrimaryContext());
DC = DC->getParent();
}
if (const auto *RD = dyn_cast<CXXRecordDecl>(PrimaryContext)) {
RD = RD->getDefinition();
if (RD) {
Info.Bases.push_back(RD);
RD->forallBases([&](const CXXRecordDecl *Base) {
Info.Bases.push_back(Base);
return false;
});
}
}
return &Info;
}
void ConfusableIdentifierCheck::check(
const ast_matchers::MatchFinder::MatchResult &Result) {
const auto *ND = Result.Nodes.getNodeAs<NamedDecl>("nameddecl");
if (!ND)
return;
IdentifierInfo *NDII = ND->getIdentifier();
if (!NDII)
return;
StringRef NDName = NDII->getName();
if (NDName.empty())
return;
const ContextInfo *Info = getContextInfo(ND->getDeclContext());
llvm::SmallVector<Entry> &Mapped = Mapper[skeleton(NDName)];
for (const Entry &E : Mapped) {
if (!mayShadow(ND, Info, E.Declaration, E.Info))
continue;
const IdentifierInfo *ONDII = E.Declaration->getIdentifier();
StringRef ONDName = ONDII->getName();
if (ONDName == NDName)
continue;
diag(ND->getLocation(), "%0 is confusable with %1") << ND << E.Declaration;
diag(E.Declaration->getLocation(), "other declaration found here",
DiagnosticIDs::Note);
}
Mapped.push_back({ND, Info});
}
void ConfusableIdentifierCheck::onEndOfTranslationUnit() {
Mapper.clear();
ContextInfos.clear();
}
void ConfusableIdentifierCheck::registerMatchers(
ast_matchers::MatchFinder *Finder) {
Finder->addMatcher(ast_matchers::namedDecl().bind("nameddecl"), this);
}
} // namespace clang::tidy::misc
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