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//=== LLVMConventionsChecker.cpp - Check LLVM codebase conventions ---*- 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
//
//===----------------------------------------------------------------------===//
//
// This defines LLVMConventionsChecker, a bunch of small little checks
// for checking specific coding conventions in the LLVM/Clang codebase.
//
//===----------------------------------------------------------------------===//
#include "clang/StaticAnalyzer/Checkers/BuiltinCheckerRegistration.h"
#include "clang/AST/DeclTemplate.h"
#include "clang/AST/StmtVisitor.h"
#include "clang/StaticAnalyzer/Core/BugReporter/BugReporter.h"
#include "clang/StaticAnalyzer/Core/Checker.h"
#include "llvm/ADT/SmallString.h"
#include "llvm/Support/raw_ostream.h"
using namespace clang;
using namespace ento;
//===----------------------------------------------------------------------===//
// Generic type checking routines.
//===----------------------------------------------------------------------===//
static bool IsLLVMStringRef(QualType T) {
const RecordType *RT = T->getAs<RecordType>();
if (!RT)
return false;
return StringRef(QualType(RT, 0).getAsString()) == "class StringRef";
}
/// Check whether the declaration is semantically inside the top-level
/// namespace named by ns.
static bool InNamespace(const Decl *D, StringRef NS) {
const NamespaceDecl *ND = dyn_cast<NamespaceDecl>(D->getDeclContext());
if (!ND)
return false;
const IdentifierInfo *II = ND->getIdentifier();
if (!II || !II->getName().equals(NS))
return false;
return isa<TranslationUnitDecl>(ND->getDeclContext());
}
static bool IsStdString(QualType T) {
if (const ElaboratedType *QT = T->getAs<ElaboratedType>())
T = QT->getNamedType();
const TypedefType *TT = T->getAs<TypedefType>();
if (!TT)
return false;
const TypedefNameDecl *TD = TT->getDecl();
if (!TD->isInStdNamespace())
return false;
return TD->getName() == "string";
}
static bool IsClangType(const RecordDecl *RD) {
return RD->getName() == "Type" && InNamespace(RD, "clang");
}
static bool IsClangDecl(const RecordDecl *RD) {
return RD->getName() == "Decl" && InNamespace(RD, "clang");
}
static bool IsClangStmt(const RecordDecl *RD) {
return RD->getName() == "Stmt" && InNamespace(RD, "clang");
}
static bool IsClangAttr(const RecordDecl *RD) {
return RD->getName() == "Attr" && InNamespace(RD, "clang");
}
static bool IsStdVector(QualType T) {
const TemplateSpecializationType *TS = T->getAs<TemplateSpecializationType>();
if (!TS)
return false;
TemplateName TM = TS->getTemplateName();
TemplateDecl *TD = TM.getAsTemplateDecl();
if (!TD || !InNamespace(TD, "std"))
return false;
return TD->getName() == "vector";
}
static bool IsSmallVector(QualType T) {
const TemplateSpecializationType *TS = T->getAs<TemplateSpecializationType>();
if (!TS)
return false;
TemplateName TM = TS->getTemplateName();
TemplateDecl *TD = TM.getAsTemplateDecl();
if (!TD || !InNamespace(TD, "llvm"))
return false;
return TD->getName() == "SmallVector";
}
//===----------------------------------------------------------------------===//
// CHECK: a StringRef should not be bound to a temporary std::string whose
// lifetime is shorter than the StringRef's.
//===----------------------------------------------------------------------===//
namespace {
class StringRefCheckerVisitor : public StmtVisitor<StringRefCheckerVisitor> {
const Decl *DeclWithIssue;
BugReporter &BR;
const CheckerBase *Checker;
public:
StringRefCheckerVisitor(const Decl *declWithIssue, BugReporter &br,
const CheckerBase *checker)
: DeclWithIssue(declWithIssue), BR(br), Checker(checker) {}
void VisitChildren(Stmt *S) {
for (Stmt *Child : S->children())
if (Child)
Visit(Child);
}
void VisitStmt(Stmt *S) { VisitChildren(S); }
void VisitDeclStmt(DeclStmt *DS);
private:
void VisitVarDecl(VarDecl *VD);
};
} // end anonymous namespace
static void CheckStringRefAssignedTemporary(const Decl *D, BugReporter &BR,
const CheckerBase *Checker) {
StringRefCheckerVisitor walker(D, BR, Checker);
walker.Visit(D->getBody());
}
void StringRefCheckerVisitor::VisitDeclStmt(DeclStmt *S) {
VisitChildren(S);
for (auto *I : S->decls())
if (VarDecl *VD = dyn_cast<VarDecl>(I))
VisitVarDecl(VD);
}
void StringRefCheckerVisitor::VisitVarDecl(VarDecl *VD) {
Expr *Init = VD->getInit();
if (!Init)
return;
// Pattern match for:
// StringRef x = call() (where call returns std::string)
if (!IsLLVMStringRef(VD->getType()))
return;
ExprWithCleanups *Ex1 = dyn_cast<ExprWithCleanups>(Init);
if (!Ex1)
return;
CXXConstructExpr *Ex2 = dyn_cast<CXXConstructExpr>(Ex1->getSubExpr());
if (!Ex2 || Ex2->getNumArgs() != 1)
return;
ImplicitCastExpr *Ex3 = dyn_cast<ImplicitCastExpr>(Ex2->getArg(0));
if (!Ex3)
return;
CXXConstructExpr *Ex4 = dyn_cast<CXXConstructExpr>(Ex3->getSubExpr());
if (!Ex4 || Ex4->getNumArgs() != 1)
return;
ImplicitCastExpr *Ex5 = dyn_cast<ImplicitCastExpr>(Ex4->getArg(0));
if (!Ex5)
return;
CXXBindTemporaryExpr *Ex6 = dyn_cast<CXXBindTemporaryExpr>(Ex5->getSubExpr());
if (!Ex6 || !IsStdString(Ex6->getType()))
return;
// Okay, badness! Report an error.
const char *desc = "StringRef should not be bound to temporary "
"std::string that it outlives";
PathDiagnosticLocation VDLoc =
PathDiagnosticLocation::createBegin(VD, BR.getSourceManager());
BR.EmitBasicReport(DeclWithIssue, Checker, desc, "LLVM Conventions", desc,
VDLoc, Init->getSourceRange());
}
//===----------------------------------------------------------------------===//
// CHECK: Clang AST nodes should not have fields that can allocate
// memory.
//===----------------------------------------------------------------------===//
static bool AllocatesMemory(QualType T) {
return IsStdVector(T) || IsStdString(T) || IsSmallVector(T);
}
// This type checking could be sped up via dynamic programming.
static bool IsPartOfAST(const CXXRecordDecl *R) {
if (IsClangStmt(R) || IsClangType(R) || IsClangDecl(R) || IsClangAttr(R))
return true;
for (const auto &BS : R->bases()) {
QualType T = BS.getType();
if (const RecordType *baseT = T->getAs<RecordType>()) {
CXXRecordDecl *baseD = cast<CXXRecordDecl>(baseT->getDecl());
if (IsPartOfAST(baseD))
return true;
}
}
return false;
}
namespace {
class ASTFieldVisitor {
SmallVector<FieldDecl*, 10> FieldChain;
const CXXRecordDecl *Root;
BugReporter &BR;
const CheckerBase *Checker;
public:
ASTFieldVisitor(const CXXRecordDecl *root, BugReporter &br,
const CheckerBase *checker)
: Root(root), BR(br), Checker(checker) {}
void Visit(FieldDecl *D);
void ReportError(QualType T);
};
} // end anonymous namespace
static void CheckASTMemory(const CXXRecordDecl *R, BugReporter &BR,
const CheckerBase *Checker) {
if (!IsPartOfAST(R))
return;
for (auto *I : R->fields()) {
ASTFieldVisitor walker(R, BR, Checker);
walker.Visit(I);
}
}
void ASTFieldVisitor::Visit(FieldDecl *D) {
FieldChain.push_back(D);
QualType T = D->getType();
if (AllocatesMemory(T))
ReportError(T);
if (const RecordType *RT = T->getAs<RecordType>()) {
const RecordDecl *RD = RT->getDecl()->getDefinition();
for (auto *I : RD->fields())
Visit(I);
}
FieldChain.pop_back();
}
void ASTFieldVisitor::ReportError(QualType T) {
SmallString<1024> buf;
llvm::raw_svector_ostream os(buf);
os << "AST class '" << Root->getName() << "' has a field '"
<< FieldChain.front()->getName() << "' that allocates heap memory";
if (FieldChain.size() > 1) {
os << " via the following chain: ";
bool isFirst = true;
for (SmallVectorImpl<FieldDecl*>::iterator I=FieldChain.begin(),
E=FieldChain.end(); I!=E; ++I) {
if (!isFirst)
os << '.';
else
isFirst = false;
os << (*I)->getName();
}
}
os << " (type " << FieldChain.back()->getType().getAsString() << ")";
// Note that this will fire for every translation unit that uses this
// class. This is suboptimal, but at least scan-build will merge
// duplicate HTML reports. In the future we need a unified way of merging
// duplicate reports across translation units. For C++ classes we cannot
// just report warnings when we see an out-of-line method definition for a
// class, as that heuristic doesn't always work (the complete definition of
// the class may be in the header file, for example).
PathDiagnosticLocation L = PathDiagnosticLocation::createBegin(
FieldChain.front(), BR.getSourceManager());
BR.EmitBasicReport(Root, Checker, "AST node allocates heap memory",
"LLVM Conventions", os.str(), L);
}
//===----------------------------------------------------------------------===//
// LLVMConventionsChecker
//===----------------------------------------------------------------------===//
namespace {
class LLVMConventionsChecker : public Checker<
check::ASTDecl<CXXRecordDecl>,
check::ASTCodeBody > {
public:
void checkASTDecl(const CXXRecordDecl *R, AnalysisManager& mgr,
BugReporter &BR) const {
if (R->isCompleteDefinition())
CheckASTMemory(R, BR, this);
}
void checkASTCodeBody(const Decl *D, AnalysisManager& mgr,
BugReporter &BR) const {
CheckStringRefAssignedTemporary(D, BR, this);
}
};
}
void ento::registerLLVMConventionsChecker(CheckerManager &mgr) {
mgr.registerChecker<LLVMConventionsChecker>();
}
bool ento::shouldRegisterLLVMConventionsChecker(const LangOptions &LO) {
return true;
}