Coverage Report

Created: 2022-01-25 06:29

/Users/buildslave/jenkins/workspace/coverage/llvm-project/clang/lib/StaticAnalyzer/Checkers/ReturnUndefChecker.cpp
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//== ReturnUndefChecker.cpp -------------------------------------*- C++ -*--==//
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//
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// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
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// See https://llvm.org/LICENSE.txt for license information.
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// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
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//
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//===----------------------------------------------------------------------===//
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//
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// This file defines ReturnUndefChecker, which is a path-sensitive
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// check which looks for undefined or garbage values being returned to the
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// caller.
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//
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//===----------------------------------------------------------------------===//
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#include "clang/StaticAnalyzer/Checkers/BuiltinCheckerRegistration.h"
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#include "clang/StaticAnalyzer/Core/BugReporter/BugType.h"
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#include "clang/StaticAnalyzer/Core/Checker.h"
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#include "clang/StaticAnalyzer/Core/CheckerManager.h"
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#include "clang/StaticAnalyzer/Core/PathSensitive/CallEvent.h"
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#include "clang/StaticAnalyzer/Core/PathSensitive/CheckerContext.h"
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using namespace clang;
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using namespace ento;
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namespace {
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class ReturnUndefChecker : public Checker< check::PreStmt<ReturnStmt> > {
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  mutable std::unique_ptr<BuiltinBug> BT_Undef;
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  mutable std::unique_ptr<BuiltinBug> BT_NullReference;
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  void emitUndef(CheckerContext &C, const Expr *RetE) const;
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  void checkReference(CheckerContext &C, const Expr *RetE,
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                      DefinedOrUnknownSVal RetVal) const;
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public:
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  void checkPreStmt(const ReturnStmt *RS, CheckerContext &C) const;
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};
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}
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void ReturnUndefChecker::checkPreStmt(const ReturnStmt *RS,
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                                      CheckerContext &C) const {
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  const Expr *RetE = RS->getRetValue();
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  if (!RetE)
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    return;
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  SVal RetVal = C.getSVal(RetE);
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  const StackFrameContext *SFC = C.getStackFrame();
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  QualType RT = CallEvent::getDeclaredResultType(SFC->getDecl());
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  if (RetVal.isUndef()) {
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    // "return;" is modeled to evaluate to an UndefinedVal. Allow UndefinedVal
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    // to be returned in functions returning void to support this pattern:
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    //   void foo() {
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    //     return;
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    //   }
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    //   void test() {
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    //     return foo();
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    //   }
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    if (!RT.isNull() && 
RT->isVoidType()53
)
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      return;
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    // Not all blocks have explicitly-specified return types; if the return type
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    // is not available, but the return value expression has 'void' type, assume
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    // Sema already checked it.
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    if (RT.isNull() && 
isa<BlockDecl>(SFC->getDecl())1
&&
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RetE->getType()->isVoidType()1
)
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      return;
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    emitUndef(C, RetE);
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    return;
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  }
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  if (RT.isNull())
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    return;
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  if (RT->isReferenceType()) {
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    checkReference(C, RetE, RetVal.castAs<DefinedOrUnknownSVal>());
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    return;
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  }
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}
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static void emitBug(CheckerContext &C, BuiltinBug &BT, const Expr *RetE,
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                    const Expr *TrackingE = nullptr) {
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  ExplodedNode *N = C.generateErrorNode();
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  if (!N)
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    return;
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  auto Report =
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      std::make_unique<PathSensitiveBugReport>(BT, BT.getDescription(), N);
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  Report->addRange(RetE->getSourceRange());
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  bugreporter::trackExpressionValue(N, TrackingE ? 
TrackingE5
:
RetE51
, *Report);
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  C.emitReport(std::move(Report));
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}
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void ReturnUndefChecker::emitUndef(CheckerContext &C, const Expr *RetE) const {
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  if (!BT_Undef)
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    BT_Undef.reset(
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        new BuiltinBug(this, "Garbage return value",
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                       "Undefined or garbage value returned to caller"));
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  emitBug(C, *BT_Undef, RetE);
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}
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void ReturnUndefChecker::checkReference(CheckerContext &C, const Expr *RetE,
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                                        DefinedOrUnknownSVal RetVal) const {
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  ProgramStateRef StNonNull, StNull;
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  std::tie(StNonNull, StNull) = C.getState()->assume(RetVal);
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  if (StNonNull) {
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    // Going forward, assume the location is non-null.
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    C.addTransition(StNonNull);
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    return;
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  }
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  // The return value is known to be null. Emit a bug report.
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  if (!BT_NullReference)
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    BT_NullReference.reset(new BuiltinBug(this, "Returning null reference"));
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  emitBug(C, *BT_NullReference, RetE, bugreporter::getDerefExpr(RetE));
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}
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void ento::registerReturnUndefChecker(CheckerManager &mgr) {
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  mgr.registerChecker<ReturnUndefChecker>();
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}
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bool ento::shouldRegisterReturnUndefChecker(const CheckerManager &mgr) {
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  return true;
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}