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llvm-project/clang/lib/StaticAnalyzer/Checkers/CallAndMessageChecker.cpp

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//===--- CallAndMessageChecker.cpp ------------------------------*- C++ -*--==//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This defines CallAndMessageChecker, a builtin checker that checks for various
// errors of call and objc message expressions.
//
//===----------------------------------------------------------------------===//
#include "ClangSACheckers.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/ObjCMessage.h"
#include "clang/StaticAnalyzer/Core/BugReporter/BugType.h"
#include "clang/AST/ParentMap.h"
#include "clang/Basic/TargetInfo.h"
#include "llvm/ADT/SmallString.h"
using namespace clang;
using namespace ento;
namespace {
class CallAndMessageChecker
: public Checker< check::PreStmt<CallExpr>, check::PreObjCMessage > {
mutable OwningPtr<BugType> BT_call_null;
mutable OwningPtr<BugType> BT_call_undef;
mutable OwningPtr<BugType> BT_call_arg;
mutable OwningPtr<BugType> BT_msg_undef;
mutable OwningPtr<BugType> BT_objc_prop_undef;
mutable OwningPtr<BugType> BT_msg_arg;
mutable OwningPtr<BugType> BT_msg_ret;
public:
void checkPreStmt(const CallExpr *CE, CheckerContext &C) const;
void checkPreObjCMessage(ObjCMessage msg, CheckerContext &C) const;
private:
static void PreVisitProcessArgs(CheckerContext &C,CallOrObjCMessage callOrMsg,
const char *BT_desc, OwningPtr<BugType> &BT);
static bool PreVisitProcessArg(CheckerContext &C, SVal V,SourceRange argRange,
const Expr *argEx,
const bool checkUninitFields,
const char *BT_desc,
OwningPtr<BugType> &BT);
static void EmitBadCall(BugType *BT, CheckerContext &C, const CallExpr *CE);
void emitNilReceiverBug(CheckerContext &C, const ObjCMessage &msg,
ExplodedNode *N) const;
void HandleNilReceiver(CheckerContext &C,
ProgramStateRef state,
ObjCMessage msg) const;
static void LazyInit_BT(const char *desc, OwningPtr<BugType> &BT) {
if (!BT)
BT.reset(new BuiltinBug(desc));
}
};
} // end anonymous namespace
void CallAndMessageChecker::EmitBadCall(BugType *BT, CheckerContext &C,
const CallExpr *CE) {
ExplodedNode *N = C.generateSink();
if (!N)
return;
BugReport *R = new BugReport(*BT, BT->getName(), N);
R->addVisitor(bugreporter::getTrackNullOrUndefValueVisitor(N,
bugreporter::GetCalleeExpr(N), R));
C.EmitReport(R);
}
void CallAndMessageChecker::PreVisitProcessArgs(CheckerContext &C,
CallOrObjCMessage callOrMsg,
const char *BT_desc,
OwningPtr<BugType> &BT) {
// Don't check for uninitialized field values in arguments if the
// caller has a body that is available and we have the chance to inline it.
// This is a hack, but is a reasonable compromise betweens sometimes warning
// and sometimes not depending on if we decide to inline a function.
const Decl *D = callOrMsg.getDecl();
const bool checkUninitFields =
!(C.getAnalysisManager().shouldInlineCall() &&
(D && D->getBody()));
for (unsigned i = 0, e = callOrMsg.getNumArgs(); i != e; ++i)
if (PreVisitProcessArg(C, callOrMsg.getArgSVal(i),
callOrMsg.getArgSourceRange(i), callOrMsg.getArg(i),
checkUninitFields,
BT_desc, BT))
return;
}
bool CallAndMessageChecker::PreVisitProcessArg(CheckerContext &C,
SVal V, SourceRange argRange,
const Expr *argEx,
const bool checkUninitFields,
const char *BT_desc,
OwningPtr<BugType> &BT) {
if (V.isUndef()) {
if (ExplodedNode *N = C.generateSink()) {
LazyInit_BT(BT_desc, BT);
// Generate a report for this bug.
BugReport *R = new BugReport(*BT, BT->getName(), N);
R->addRange(argRange);
if (argEx)
R->addVisitor(bugreporter::getTrackNullOrUndefValueVisitor(N, argEx,
R));
C.EmitReport(R);
}
return true;
}
if (!checkUninitFields)
return false;
if (const nonloc::LazyCompoundVal *LV =
dyn_cast<nonloc::LazyCompoundVal>(&V)) {
class FindUninitializedField {
public:
SmallVector<const FieldDecl *, 10> FieldChain;
private:
ASTContext &C;
StoreManager &StoreMgr;
MemRegionManager &MrMgr;
Store store;
public:
FindUninitializedField(ASTContext &c, StoreManager &storeMgr,
MemRegionManager &mrMgr, Store s)
: C(c), StoreMgr(storeMgr), MrMgr(mrMgr), store(s) {}
bool Find(const TypedValueRegion *R) {
QualType T = R->getValueType();
if (const RecordType *RT = T->getAsStructureType()) {
const RecordDecl *RD = RT->getDecl()->getDefinition();
assert(RD && "Referred record has no definition");
for (RecordDecl::field_iterator I =
RD->field_begin(), E = RD->field_end(); I!=E; ++I) {
const FieldRegion *FR = MrMgr.getFieldRegion(&*I, R);
FieldChain.push_back(&*I);
T = I->getType();
if (T->getAsStructureType()) {
if (Find(FR))
return true;
}
else {
const SVal &V = StoreMgr.getBinding(store, loc::MemRegionVal(FR));
if (V.isUndef())
return true;
}
FieldChain.pop_back();
}
}
return false;
}
};
const LazyCompoundValData *D = LV->getCVData();
FindUninitializedField F(C.getASTContext(),
C.getState()->getStateManager().getStoreManager(),
C.getSValBuilder().getRegionManager(),
D->getStore());
if (F.Find(D->getRegion())) {
if (ExplodedNode *N = C.generateSink()) {
LazyInit_BT(BT_desc, BT);
SmallString<512> Str;
llvm::raw_svector_ostream os(Str);
os << "Passed-by-value struct argument contains uninitialized data";
if (F.FieldChain.size() == 1)
os << " (e.g., field: '" << *F.FieldChain[0] << "')";
else {
os << " (e.g., via the field chain: '";
bool first = true;
for (SmallVectorImpl<const FieldDecl *>::iterator
DI = F.FieldChain.begin(), DE = F.FieldChain.end(); DI!=DE;++DI){
if (first)
first = false;
else
os << '.';
os << **DI;
}
os << "')";
}
// Generate a report for this bug.
BugReport *R = new BugReport(*BT, os.str(), N);
R->addRange(argRange);
// FIXME: enhance track back for uninitialized value for arbitrary
// memregions
C.EmitReport(R);
}
return true;
}
}
return false;
}
void CallAndMessageChecker::checkPreStmt(const CallExpr *CE,
CheckerContext &C) const{
const Expr *Callee = CE->getCallee()->IgnoreParens();
const LocationContext *LCtx = C.getLocationContext();
SVal L = C.getState()->getSVal(Callee, LCtx);
if (L.isUndef()) {
if (!BT_call_undef)
BT_call_undef.reset(new BuiltinBug("Called function pointer is an "
"uninitalized pointer value"));
EmitBadCall(BT_call_undef.get(), C, CE);
return;
}
if (isa<loc::ConcreteInt>(L)) {
if (!BT_call_null)
BT_call_null.reset(
new BuiltinBug("Called function pointer is null (null dereference)"));
EmitBadCall(BT_call_null.get(), C, CE);
}
PreVisitProcessArgs(C, CallOrObjCMessage(CE, C.getState(), LCtx),
"Function call argument is an uninitialized value",
BT_call_arg);
}
void CallAndMessageChecker::checkPreObjCMessage(ObjCMessage msg,
CheckerContext &C) const {
ProgramStateRef state = C.getState();
const LocationContext *LCtx = C.getLocationContext();
// FIXME: Handle 'super'?
if (const Expr *receiver = msg.getInstanceReceiver()) {
SVal recVal = state->getSVal(receiver, LCtx);
if (recVal.isUndef()) {
if (ExplodedNode *N = C.generateSink()) {
BugType *BT = 0;
if (msg.isPureMessageExpr()) {
if (!BT_msg_undef)
BT_msg_undef.reset(new BuiltinBug("Receiver in message expression "
"is an uninitialized value"));
BT = BT_msg_undef.get();
}
else {
if (!BT_objc_prop_undef)
BT_objc_prop_undef.reset(new BuiltinBug("Property access on an "
"uninitialized object pointer"));
BT = BT_objc_prop_undef.get();
}
BugReport *R =
new BugReport(*BT, BT->getName(), N);
R->addRange(receiver->getSourceRange());
R->addVisitor(bugreporter::getTrackNullOrUndefValueVisitor(N,
receiver,
R));
C.EmitReport(R);
}
return;
} else {
// Bifurcate the state into nil and non-nil ones.
DefinedOrUnknownSVal receiverVal = cast<DefinedOrUnknownSVal>(recVal);
ProgramStateRef notNilState, nilState;
llvm::tie(notNilState, nilState) = state->assume(receiverVal);
// Handle receiver must be nil.
if (nilState && !notNilState) {
HandleNilReceiver(C, state, msg);
return;
}
}
}
const char *bugDesc = msg.isPropertySetter() ?
"Argument for property setter is an uninitialized value"
: "Argument in message expression is an uninitialized value";
// Check for any arguments that are uninitialized/undefined.
PreVisitProcessArgs(C, CallOrObjCMessage(msg, state, LCtx),
bugDesc, BT_msg_arg);
}
void CallAndMessageChecker::emitNilReceiverBug(CheckerContext &C,
const ObjCMessage &msg,
ExplodedNode *N) const {
if (!BT_msg_ret)
BT_msg_ret.reset(
new BuiltinBug("Receiver in message expression is "
"'nil' and returns a garbage value"));
SmallString<200> buf;
llvm::raw_svector_ostream os(buf);
os << "The receiver of message '" << msg.getSelector().getAsString()
<< "' is nil and returns a value of type '"
<< msg.getType(C.getASTContext()).getAsString() << "' that will be garbage";
BugReport *report = new BugReport(*BT_msg_ret, os.str(), N);
if (const Expr *receiver = msg.getInstanceReceiver()) {
report->addRange(receiver->getSourceRange());
report->addVisitor(bugreporter::getTrackNullOrUndefValueVisitor(N,
receiver,
report));
}
C.EmitReport(report);
}
static bool supportsNilWithFloatRet(const llvm::Triple &triple) {
return (triple.getVendor() == llvm::Triple::Apple &&
(triple.getOS() == llvm::Triple::IOS ||
!triple.isMacOSXVersionLT(10,5)));
}
void CallAndMessageChecker::HandleNilReceiver(CheckerContext &C,
ProgramStateRef state,
ObjCMessage msg) const {
ASTContext &Ctx = C.getASTContext();
// Check the return type of the message expression. A message to nil will
// return different values depending on the return type and the architecture.
QualType RetTy = msg.getType(Ctx);
CanQualType CanRetTy = Ctx.getCanonicalType(RetTy);
const LocationContext *LCtx = C.getLocationContext();
if (CanRetTy->isStructureOrClassType()) {
// Structure returns are safe since the compiler zeroes them out.
SVal V = C.getSValBuilder().makeZeroVal(msg.getType(Ctx));
C.addTransition(state->BindExpr(msg.getMessageExpr(), LCtx, V));
return;
}
// Other cases: check if sizeof(return type) > sizeof(void*)
if (CanRetTy != Ctx.VoidTy && C.getLocationContext()->getParentMap()
.isConsumedExpr(msg.getMessageExpr())) {
// Compute: sizeof(void *) and sizeof(return type)
const uint64_t voidPtrSize = Ctx.getTypeSize(Ctx.VoidPtrTy);
const uint64_t returnTypeSize = Ctx.getTypeSize(CanRetTy);
if (voidPtrSize < returnTypeSize &&
!(supportsNilWithFloatRet(Ctx.getTargetInfo().getTriple()) &&
(Ctx.FloatTy == CanRetTy ||
Ctx.DoubleTy == CanRetTy ||
Ctx.LongDoubleTy == CanRetTy ||
Ctx.LongLongTy == CanRetTy ||
Ctx.UnsignedLongLongTy == CanRetTy))) {
if (ExplodedNode *N = C.generateSink(state))
emitNilReceiverBug(C, msg, N);
return;
}
// Handle the safe cases where the return value is 0 if the
// receiver is nil.
//
// FIXME: For now take the conservative approach that we only
// return null values if we *know* that the receiver is nil.
// This is because we can have surprises like:
//
// ... = [[NSScreens screens] objectAtIndex:0];
//
// What can happen is that [... screens] could return nil, but
// it most likely isn't nil. We should assume the semantics
// of this case unless we have *a lot* more knowledge.
//
SVal V = C.getSValBuilder().makeZeroVal(msg.getType(Ctx));
C.addTransition(state->BindExpr(msg.getMessageExpr(), LCtx, V));
return;
}
C.addTransition(state);
}
void ento::registerCallAndMessageChecker(CheckerManager &mgr) {
mgr.registerChecker<CallAndMessageChecker>();
}
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