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//== ReturnUndefChecker.cpp -------------------------------------*- C++ -*--==//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This file defines ReturnUndefChecker, which is a path-sensitive
// check which looks for undefined or garbage values being returned to the
// caller.
//
//===----------------------------------------------------------------------===//
#include "clang/StaticAnalyzer/Checkers/BuiltinCheckerRegistration.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 ReturnUndefChecker : public Checker< check::PreStmt<ReturnStmt> > {
mutable std::unique_ptr<BuiltinBug> BT_Undef;
mutable std::unique_ptr<BuiltinBug> BT_NullReference;
void emitUndef(CheckerContext &C, const Expr *RetE) const;
void checkReference(CheckerContext &C, const Expr *RetE,
DefinedOrUnknownSVal RetVal) const;
public:
void checkPreStmt(const ReturnStmt *RS, CheckerContext &C) const;
};
}
void ReturnUndefChecker::checkPreStmt(const ReturnStmt *RS,
CheckerContext &C) const {
const Expr *RetE = RS->getRetValue();
if (!RetE)
return;
SVal RetVal = C.getSVal(RetE);
const StackFrameContext *SFC = C.getStackFrame();
QualType RT = CallEvent::getDeclaredResultType(SFC->getDecl());
if (RetVal.isUndef()) {
// "return;" is modeled to evaluate to an UndefinedVal. Allow UndefinedVal
// to be returned in functions returning void to support this pattern:
// void foo() {
// return;
// }
// void test() {
// return foo();
// }
if (!RT.isNull() && RT->isVoidType())
return;
// Not all blocks have explicitly-specified return types; if the return type
// is not available, but the return value expression has 'void' type, assume
// Sema already checked it.
if (RT.isNull() && isa<BlockDecl>(SFC->getDecl()) &&
RetE->getType()->isVoidType())
return;
emitUndef(C, RetE);
return;
}
if (RT.isNull())
return;
if (RT->isReferenceType()) {
checkReference(C, RetE, RetVal.castAs<DefinedOrUnknownSVal>());
return;
}
}
static void emitBug(CheckerContext &C, BuiltinBug &BT, const Expr *RetE,
const Expr *TrackingE = nullptr) {
ExplodedNode *N = C.generateErrorNode();
if (!N)
return;
auto Report = llvm::make_unique<BugReport>(BT, BT.getDescription(), N);
Report->addRange(RetE->getSourceRange());
bugreporter::trackExpressionValue(N, TrackingE ? TrackingE : RetE, *Report);
C.emitReport(std::move(Report));
}
void ReturnUndefChecker::emitUndef(CheckerContext &C, const Expr *RetE) const {
if (!BT_Undef)
BT_Undef.reset(
new BuiltinBug(this, "Garbage return value",
"Undefined or garbage value returned to caller"));
emitBug(C, *BT_Undef, RetE);
}
void ReturnUndefChecker::checkReference(CheckerContext &C, const Expr *RetE,
DefinedOrUnknownSVal RetVal) const {
ProgramStateRef StNonNull, StNull;
std::tie(StNonNull, StNull) = C.getState()->assume(RetVal);
if (StNonNull) {
// Going forward, assume the location is non-null.
C.addTransition(StNonNull);
return;
}
// The return value is known to be null. Emit a bug report.
if (!BT_NullReference)
BT_NullReference.reset(new BuiltinBug(this, "Returning null reference"));
emitBug(C, *BT_NullReference, RetE, bugreporter::getDerefExpr(RetE));
}
void ento::registerReturnUndefChecker(CheckerManager &mgr) {
mgr.registerChecker<ReturnUndefChecker>();
}
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