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//== ObjCContainersASTChecker.cpp - CoreFoundation containers API *- 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
//
//===----------------------------------------------------------------------===//
//
// An AST checker that looks for common pitfalls when using 'CFArray',
// 'CFDictionary', 'CFSet' APIs.
//
//===----------------------------------------------------------------------===//
#include "clang/StaticAnalyzer/Checkers/BuiltinCheckerRegistration.h"
#include "clang/AST/StmtVisitor.h"
#include "clang/Analysis/AnalysisDeclContext.h"
#include "clang/Basic/TargetInfo.h"
#include "clang/StaticAnalyzer/Core/BugReporter/BugReporter.h"
#include "clang/StaticAnalyzer/Core/Checker.h"
#include "clang/StaticAnalyzer/Core/PathSensitive/AnalysisManager.h"
#include "llvm/ADT/SmallString.h"
#include "llvm/Support/raw_ostream.h"
using namespace clang;
using namespace ento;
namespace {
class WalkAST : public StmtVisitor<WalkAST> {
BugReporter &BR;
const CheckerBase *Checker;
AnalysisDeclContext* AC;
ASTContext &ASTC;
uint64_t PtrWidth;
/// Check if the type has pointer size (very conservative).
inline bool isPointerSize(const Type *T) {
if (!T)
return true;
if (T->isIncompleteType())
return true;
return (ASTC.getTypeSize(T) == PtrWidth);
}
/// Check if the type is a pointer/array to pointer sized values.
inline bool hasPointerToPointerSizedType(const Expr *E) {
QualType T = E->getType();
// The type could be either a pointer or array.
const Type *TP = T.getTypePtr();
QualType PointeeT = TP->getPointeeType();
if (!PointeeT.isNull()) {
// If the type is a pointer to an array, check the size of the array
// elements. To avoid false positives coming from assumption that the
// values x and &x are equal when x is an array.
if (const Type *TElem = PointeeT->getArrayElementTypeNoTypeQual())
if (isPointerSize(TElem))
return true;
// Else, check the pointee size.
return isPointerSize(PointeeT.getTypePtr());
}
if (const Type *TElem = TP->getArrayElementTypeNoTypeQual())
return isPointerSize(TElem);
// The type must be an array/pointer type.
// This could be a null constant, which is allowed.
return static_cast<bool>(
E->isNullPointerConstant(ASTC, Expr::NPC_ValueDependentIsNull));
}
public:
WalkAST(BugReporter &br, const CheckerBase *checker, AnalysisDeclContext *ac)
: BR(br), Checker(checker), AC(ac), ASTC(AC->getASTContext()),
PtrWidth(ASTC.getTargetInfo().getPointerWidth(0)) {}
// Statement visitor methods.
void VisitChildren(Stmt *S);
void VisitStmt(Stmt *S) { VisitChildren(S); }
void VisitCallExpr(CallExpr *CE);
};
} // end anonymous namespace
static StringRef getCalleeName(CallExpr *CE) {
const FunctionDecl *FD = CE->getDirectCallee();
if (!FD)
return StringRef();
IdentifierInfo *II = FD->getIdentifier();
if (!II) // if no identifier, not a simple C function
return StringRef();
return II->getName();
}
void WalkAST::VisitCallExpr(CallExpr *CE) {
StringRef Name = getCalleeName(CE);
if (Name.empty())
return;
const Expr *Arg = nullptr;
unsigned ArgNum;
if (Name.equals("CFArrayCreate") || Name.equals("CFSetCreate")) {
if (CE->getNumArgs() != 4)
return;
ArgNum = 1;
Arg = CE->getArg(ArgNum)->IgnoreParenCasts();
if (hasPointerToPointerSizedType(Arg))
return;
} else if (Name.equals("CFDictionaryCreate")) {
if (CE->getNumArgs() != 6)
return;
// Check first argument.
ArgNum = 1;
Arg = CE->getArg(ArgNum)->IgnoreParenCasts();
if (hasPointerToPointerSizedType(Arg)) {
// Check second argument.
ArgNum = 2;
Arg = CE->getArg(ArgNum)->IgnoreParenCasts();
if (hasPointerToPointerSizedType(Arg))
// Both are good, return.
return;
}
}
if (Arg) {
assert(ArgNum == 1 || ArgNum == 2);
SmallString<64> BufName;
llvm::raw_svector_ostream OsName(BufName);
OsName << " Invalid use of '" << Name << "'" ;
SmallString<256> Buf;
llvm::raw_svector_ostream Os(Buf);
// Use "second" and "third" since users will expect 1-based indexing
// for parameter names when mentioned in prose.
Os << " The "<< ((ArgNum == 1) ? "second" : "third") << " argument to '"
<< Name << "' must be a C array of pointer-sized values, not '"
<< Arg->getType().getAsString() << "'";
PathDiagnosticLocation CELoc =
PathDiagnosticLocation::createBegin(CE, BR.getSourceManager(), AC);
BR.EmitBasicReport(AC->getDecl(), Checker, OsName.str(),
categories::CoreFoundationObjectiveC, Os.str(), CELoc,
Arg->getSourceRange());
}
// Recurse and check children.
VisitChildren(CE);
}
void WalkAST::VisitChildren(Stmt *S) {
for (Stmt *Child : S->children())
if (Child)
Visit(Child);
}
namespace {
class ObjCContainersASTChecker : public Checker<check::ASTCodeBody> {
public:
void checkASTCodeBody(const Decl *D, AnalysisManager& Mgr,
BugReporter &BR) const {
WalkAST walker(BR, this, Mgr.getAnalysisDeclContext(D));
walker.Visit(D->getBody());
}
};
}
void ento::registerObjCContainersASTChecker(CheckerManager &mgr) {
mgr.registerChecker<ObjCContainersASTChecker>();
}
bool ento::shouldRegisterObjCContainersASTChecker(const CheckerManager &mgr) {
return true;
}
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