| //== 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 "ClangSACheckers.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.generateSink(); |
| if (!N) |
| return; |
| |
| BugReport *Report = new BugReport(BT, BT.getDescription(), N); |
| |
| Report->addRange(RetE->getSourceRange()); |
| bugreporter::trackNullOrUndefValue(N, TrackingE ? TrackingE : RetE, *Report); |
| |
| C.emitReport(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>(); |
| } |