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

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//===--- NonNullParamChecker.cpp - Undefined arguments checker -*- C++ -*--===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This defines NonNullParamChecker, which checks for arguments expected not to
// be null due to:
// - the corresponding parameters being declared to have nonnull attribute
// - the corresponding parameters being references; since the call would form
// a reference to a null pointer
//
//===----------------------------------------------------------------------===//
#include "ClangSACheckers.h"
#include "clang/AST/Attr.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/CallEvent.h"
#include "clang/StaticAnalyzer/Core/PathSensitive/CheckerContext.h"
using namespace clang;
using namespace ento;
namespace {
class NonNullParamChecker
: public Checker< check::PreCall > {
mutable OwningPtr<BugType> BTAttrNonNull;
mutable OwningPtr<BugType> BTNullRefArg;
public:
void checkPreCall(const CallEvent &Call, CheckerContext &C) const;
BugReport *genReportNullAttrNonNull(const ExplodedNode *ErrorN,
const Expr *ArgE) const;
BugReport *genReportReferenceToNullPointer(const ExplodedNode *ErrorN,
const Expr *ArgE) const;
};
} // end anonymous namespace
void NonNullParamChecker::checkPreCall(const CallEvent &Call,
CheckerContext &C) const {
const Decl *FD = Call.getDecl();
if (!FD)
return;
const NonNullAttr *Att = FD->getAttr<NonNullAttr>();
ProgramStateRef state = C.getState();
CallEvent::param_type_iterator TyI = Call.param_type_begin(),
TyE = Call.param_type_end();
for (unsigned idx = 0, count = Call.getNumArgs(); idx != count; ++idx){
// Check if the parameter is a reference. We want to report when reference
// to a null pointer is passed as a paramter.
bool haveRefTypeParam = false;
if (TyI != TyE) {
haveRefTypeParam = (*TyI)->isReferenceType();
TyI++;
}
bool haveAttrNonNull = Att && Att->isNonNull(idx);
if (!haveRefTypeParam && !haveAttrNonNull)
continue;
// If the value is unknown or undefined, we can't perform this check.
const Expr *ArgE = Call.getArgExpr(idx);
SVal V = Call.getArgSVal(idx);
Optional<DefinedSVal> DV = V.getAs<DefinedSVal>();
if (!DV)
continue;
// Process the case when the argument is not a location.
assert(!haveRefTypeParam || DV->getAs<Loc>());
if (haveAttrNonNull && !DV->getAs<Loc>()) {
// If the argument is a union type, we want to handle a potential
// transparent_union GCC extension.
if (!ArgE)
continue;
QualType T = ArgE->getType();
const RecordType *UT = T->getAsUnionType();
if (!UT || !UT->getDecl()->hasAttr<TransparentUnionAttr>())
continue;
if (Optional<nonloc::CompoundVal> CSV =
DV->getAs<nonloc::CompoundVal>()) {
nonloc::CompoundVal::iterator CSV_I = CSV->begin();
assert(CSV_I != CSV->end());
V = *CSV_I;
DV = V.getAs<DefinedSVal>();
assert(++CSV_I == CSV->end());
if (!DV)
continue;
// Retrieve the corresponding expression.
if (const CompoundLiteralExpr *CE = dyn_cast<CompoundLiteralExpr>(ArgE))
if (const InitListExpr *IE =
dyn_cast<InitListExpr>(CE->getInitializer()))
ArgE = dyn_cast<Expr>(*(IE->begin()));
} else {
// FIXME: Handle LazyCompoundVals?
continue;
}
}
ConstraintManager &CM = C.getConstraintManager();
ProgramStateRef stateNotNull, stateNull;
llvm::tie(stateNotNull, stateNull) = CM.assumeDual(state, *DV);
if (stateNull && !stateNotNull) {
// Generate an error node. Check for a null node in case
// we cache out.
if (ExplodedNode *errorNode = C.generateSink(stateNull)) {
BugReport *R = 0;
if (haveAttrNonNull)
R = genReportNullAttrNonNull(errorNode, ArgE);
else if (haveRefTypeParam)
R = genReportReferenceToNullPointer(errorNode, ArgE);
// Highlight the range of the argument that was null.
R->addRange(Call.getArgSourceRange(idx));
// Emit the bug report.
C.emitReport(R);
}
// Always return. Either we cached out or we just emitted an error.
return;
}
// If a pointer value passed the check we should assume that it is
// indeed not null from this point forward.
assert(stateNotNull);
state = stateNotNull;
}
// If we reach here all of the arguments passed the nonnull check.
// If 'state' has been updated generated a new node.
C.addTransition(state);
}
BugReport *NonNullParamChecker::genReportNullAttrNonNull(
const ExplodedNode *ErrorNode, const Expr *ArgE) const {
// Lazily allocate the BugType object if it hasn't already been
// created. Ownership is transferred to the BugReporter object once
// the BugReport is passed to 'EmitWarning'.
if (!BTAttrNonNull)
BTAttrNonNull.reset(new BugType(
"Argument with 'nonnull' attribute passed null",
"API"));
BugReport *R = new BugReport(*BTAttrNonNull,
"Null pointer passed as an argument to a 'nonnull' parameter",
ErrorNode);
if (ArgE)
bugreporter::trackNullOrUndefValue(ErrorNode, ArgE, *R);
return R;
}
BugReport *NonNullParamChecker::genReportReferenceToNullPointer(
const ExplodedNode *ErrorNode, const Expr *ArgE) const {
if (!BTNullRefArg)
BTNullRefArg.reset(new BuiltinBug("Dereference of null pointer"));
BugReport *R = new BugReport(*BTNullRefArg,
"Forming reference to null pointer",
ErrorNode);
if (ArgE) {
const Expr *ArgEDeref = bugreporter::getDerefExpr(ArgE);
if (ArgEDeref == 0)
ArgEDeref = ArgE;
bugreporter::trackNullOrUndefValue(ErrorNode,
ArgEDeref,
*R);
}
return R;
}
void ento::registerNonNullParamChecker(CheckerManager &mgr) {
mgr.registerChecker<NonNullParamChecker>();
}