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// MacOSXAPIChecker.h - Checks proper use of various MacOS X APIs --*- C++ -*-//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
// This defines MacOSXAPIChecker, which is an assortment of checks on calls
// to various, widely used Apple APIs.
// FIXME: What's currently in BasicObjCFoundationChecks.cpp should be migrated
// to here, using the new Checker interface.
#include "clang/StaticAnalyzer/Checkers/BuiltinCheckerRegistration.h"
#include "clang/Basic/TargetInfo.h"
#include "clang/StaticAnalyzer/Core/BugReporter/BugType.h"
#include "clang/StaticAnalyzer/Core/Checker.h"
#include "clang/StaticAnalyzer/Core/CheckerManager.h"
#include "clang/StaticAnalyzer/Core/PathSensitive/CheckerContext.h"
#include "clang/StaticAnalyzer/Core/PathSensitive/ProgramStateTrait.h"
#include "llvm/ADT/SmallString.h"
#include "llvm/ADT/StringSwitch.h"
#include "llvm/Support/raw_ostream.h"
using namespace clang;
using namespace ento;
namespace {
class MacOSXAPIChecker : public Checker< check::PreStmt<CallExpr> > {
mutable std::unique_ptr<BugType> BT_dispatchOnce;
static const ObjCIvarRegion *getParentIvarRegion(const MemRegion *R);
void checkPreStmt(const CallExpr *CE, CheckerContext &C) const;
void CheckDispatchOnce(CheckerContext &C, const CallExpr *CE,
StringRef FName) const;
typedef void (MacOSXAPIChecker::*SubChecker)(CheckerContext &,
const CallExpr *,
StringRef FName) const;
} //end anonymous namespace
// dispatch_once and dispatch_once_f
const ObjCIvarRegion *
MacOSXAPIChecker::getParentIvarRegion(const MemRegion *R) {
const SubRegion *SR = dyn_cast<SubRegion>(R);
while (SR) {
if (const ObjCIvarRegion *IR = dyn_cast<ObjCIvarRegion>(SR))
return IR;
SR = dyn_cast<SubRegion>(SR->getSuperRegion());
return nullptr;
void MacOSXAPIChecker::CheckDispatchOnce(CheckerContext &C, const CallExpr *CE,
StringRef FName) const {
if (CE->getNumArgs() < 1)
// Check if the first argument is improperly allocated. If so, issue a
// warning because that's likely to be bad news.
const MemRegion *R = C.getSVal(CE->getArg(0)).getAsRegion();
if (!R)
// Global variables are fine.
const MemRegion *RB = R->getBaseRegion();
const MemSpaceRegion *RS = RB->getMemorySpace();
if (isa<GlobalsSpaceRegion>(RS))
// Handle _dispatch_once. In some versions of the OS X SDK we have the case
// that dispatch_once is a macro that wraps a call to _dispatch_once.
// _dispatch_once is then a function which then calls the real dispatch_once.
// Users do not care; they just want the warning at the top-level call.
if (CE->getBeginLoc().isMacroID()) {
StringRef TrimmedFName = FName.ltrim('_');
if (TrimmedFName != FName)
FName = TrimmedFName;
SmallString<256> S;
llvm::raw_svector_ostream os(S);
bool SuggestStatic = false;
os << "Call to '" << FName << "' uses";
if (const VarRegion *VR = dyn_cast<VarRegion>(RB)) {
const VarDecl *VD = VR->getDecl();
// FIXME: These should have correct memory space and thus should be filtered
// out earlier. This branch only fires when we're looking from a block,
// which we analyze as a top-level declaration, onto a static local
// in a function that contains the block.
if (VD->isStaticLocal())
// We filtered out globals earlier, so it must be a local variable
// or a block variable which is under UnknownSpaceRegion.
if (VR != R)
os << " memory within";
if (VD->hasAttr<BlocksAttr>())
os << " the block variable '";
os << " the local variable '";
os << VR->getDecl()->getName() << '\'';
SuggestStatic = true;
} else if (const ObjCIvarRegion *IVR = getParentIvarRegion(R)) {
if (IVR != R)
os << " memory within";
os << " the instance variable '" << IVR->getDecl()->getName() << '\'';
} else if (isa<HeapSpaceRegion>(RS)) {
os << " heap-allocated memory";
} else if (isa<UnknownSpaceRegion>(RS)) {
// Presence of an IVar superregion has priority over this branch, because
// ObjC objects are on the heap even if the core doesn't realize this.
// Presence of a block variable base region has priority over this branch,
// because block variables are known to be either on stack or on heap
// (might actually move between the two, hence UnknownSpace).
} else {
os << " stack allocated memory";
os << " for the predicate value. Using such transient memory for "
"the predicate is potentially dangerous.";
if (SuggestStatic)
os << " Perhaps you intended to declare the variable as 'static'?";
ExplodedNode *N = C.generateErrorNode();
if (!N)
if (!BT_dispatchOnce)
BT_dispatchOnce.reset(new BugType(this, "Improper use of 'dispatch_once'",
"API Misuse (Apple)"));
auto report =
std::make_unique<PathSensitiveBugReport>(*BT_dispatchOnce, os.str(), N);
// Central dispatch function.
void MacOSXAPIChecker::checkPreStmt(const CallExpr *CE,
CheckerContext &C) const {
StringRef Name = C.getCalleeName(CE);
if (Name.empty())
SubChecker SC =
if (SC)
(this->*SC)(C, CE, Name);
// Registration.
void ento::registerMacOSXAPIChecker(CheckerManager &mgr) {
bool ento::shouldRegisterMacOSXAPIChecker(const LangOptions &LO) {
return true;