llvm/clang/lib/StaticAnalyzer/Checkers/GTestChecker.cpp

//==- GTestChecker.cpp - Model gtest API --*- C++ -*-==//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
//
// This checker models the behavior of un-inlined APIs from the gtest
// unit-testing library to avoid false positives when using assertions from
// that library.
//
//===----------------------------------------------------------------------===//

#include "clang/StaticAnalyzer/Checkers/BuiltinCheckerRegistration.h"
#include "clang/AST/Expr.h"
#include "clang/Basic/LangOptions.h"
#include "clang/StaticAnalyzer/Core/Checker.h"
#include "clang/StaticAnalyzer/Core/PathSensitive/CallEvent.h"
#include "clang/StaticAnalyzer/Core/PathSensitive/CheckerContext.h"
#include "clang/StaticAnalyzer/Core/PathSensitive/ProgramState.h"
#include "llvm/Support/raw_ostream.h"
#include <optional>

usingnamespaceclang;
usingnamespaceento;

// Modeling of un-inlined AssertionResult constructors
//
// The gtest unit testing API provides macros for assertions that expand
// into an if statement that calls a series of constructors and returns
// when the "assertion" is false.
//
// For example,
//
//   ASSERT_TRUE(a == b)
//
// expands into:
//
//   switch (0)
//   case 0:
//   default:
//     if (const ::testing::AssertionResult gtest_ar_ =
//             ::testing::AssertionResult((a == b)))
//       ;
//     else
//       return ::testing::internal::AssertHelper(
//                  ::testing::TestPartResult::kFatalFailure,
//                  "<path to project>",
//                  <line number>,
//                  ::testing::internal::GetBoolAssertionFailureMessage(
//                      gtest_ar_, "a == b", "false", "true")
//                      .c_str()) = ::testing::Message();
//
// where AssertionResult is defined similarly to
//
//   class AssertionResult {
//   public:
//     AssertionResult(const AssertionResult& other);
//     explicit AssertionResult(bool success) : success_(success) {}
//     operator bool() const { return success_; }
//     ...
//     private:
//     bool success_;
//   };
//
// In order for the analyzer to correctly handle this assertion, it needs to
// know that the boolean value of the expression "a == b" is stored the
// 'success_' field of the original AssertionResult temporary and propagated
// (via the copy constructor) into the 'success_' field of the object stored
// in 'gtest_ar_'.  That boolean value will then be returned from the bool
// conversion method in the if statement. This guarantees that the assertion
// holds when the return path is not taken.
//
// If the success value is not properly propagated, then the eager case split
// on evaluating the expression can cause pernicious false positives
// on the non-return path:
//
//   ASSERT(ptr != NULL)
//   *ptr = 7; // False positive null pointer dereference here
//
// Unfortunately, the bool constructor cannot be inlined (because its
// implementation is not present in the headers) and the copy constructor is
// not inlined (because it is constructed into a temporary and the analyzer
// does not inline these since it does not yet reliably call temporary
// destructors).
//
// This checker compensates for the missing inlining by propagating the
// _success value across the bool and copy constructors so the assertion behaves
// as expected.

namespace {
class GTestChecker : public Checker<check::PostCall> { … };
} // End anonymous namespace.

/// Model a call to an un-inlined AssertionResult(bool) or
/// AssertionResult(bool &, ...).
/// To do so, constrain the value of the newly-constructed instance's 'success_'
/// field to be equal to the passed-in boolean value.
///
/// \param IsRef Whether the boolean parameter is a reference or not.
void GTestChecker::modelAssertionResultBoolConstructor(
    const CXXConstructorCall *Call, bool IsRef, CheckerContext &C) const { … }

/// Model a call to an un-inlined AssertionResult copy constructor:
///
///   AssertionResult(const &AssertionResult other)
///
/// To do so, constrain the value of the newly-constructed instance's
/// 'success_' field to be equal to the value of the pass-in instance's
/// 'success_' field.
void GTestChecker::modelAssertionResultCopyConstructor(
    const CXXConstructorCall *Call, CheckerContext &C) const { … }

/// Model calls to AssertionResult constructors that are not inlined.
void GTestChecker::checkPostCall(const CallEvent &Call,
                                 CheckerContext &C) const { … }

void GTestChecker::initIdentifierInfo(ASTContext &Ctx) const { … }

/// Returns the value stored in the 'success_' field of the passed-in
/// AssertionResult instance.
SVal GTestChecker::getAssertionResultSuccessFieldValue(
    const CXXRecordDecl *AssertionResultDecl, SVal Instance,
    ProgramStateRef State) const { … }

/// Constrain the passed-in state to assume two values are equal.
ProgramStateRef GTestChecker::assumeValuesEqual(SVal Val1, SVal Val2,
                                                ProgramStateRef State,
                                                CheckerContext &C) { … }

void ento::registerGTestChecker(CheckerManager &Mgr) { … }

bool ento::shouldRegisterGTestChecker(const CheckerManager &mgr) { … }