測驗|測驗在隨機索引處將隨機生成的值插入到動態陣列時出現段錯誤-有解無憂

我創建了一個自定義的通用 DynamicArray 類，其中一切正常，除了在測驗 add() 方法時，我在該方法中將元素添加到特定索引。

我正在使用 gtest 框架進行測驗，更具體地說，我正在使用型別引數化測驗來創建測驗用例。我針對這些型別（int、int*、char*、char*、std::string）運行測驗，我創建了為我生成隨機值的函式，并在我的測驗用例中使用它們。

問題是有時我會遇到段錯誤，而其他時候則不會。

這是我的專案的結構：

build/
include/
   structs/
      DynamicArray.h
src/
   main.cpp
tests/
   TestCases/
      DynamicArrayTest.cpp
   TestClasses/
      DynamicArrayTest.h
   TestHelpers/
      generators.h
   test_runner.cpp
CMakeLists.txt

CMakeLists.txt:

# cmake version and project info

############################################################################

# Variables 
# Compile flags

SET(GCC_DEBUGGING_COMPILE_FLAGS "-Wall -ggdb3")
SET(CMAKE_CXX_FLAGS  "${CMAKE_CXX_FLAGS} ${GCC_DEBUGGING_COMPILE_FLAGS}")

set(SRCS
    src/main.cpp
)

set(EXEC_SRCS
    src/main.cpp
)

set(HEADERS
    include/structs/structures.h
)

set(TEST_SRCS
    tests/TestCases/DynamicArrayTest.cpp
    tests/test_runner.cpp
)
############################################################################

# Gtest

include(FetchContent)
FetchContent_Declare(
  googletest
  URL https://github.com/google/googletest/archive/03597a01ee50ed33e9dfd640b249b4be3799d395.zip
)
# For Windows: Prevent overriding the parent project's compiler/linker settings
set(gtest_force_shared_crt ON CACHE BOOL "" FORCE)
FetchContent_MakeAvailable(googletest)

############################################################################
## 
# Build targets
##

if(${PROJECT_NAME}_BUILD_EXECUTABLE)

    add_executable(${PROJECT_NAME} ${EXEC_SRCS} ${SRCS})

    if(${PROJECT_NAME}_ENABLE_UNIT_TESTING)
        add_library(${PROJECT_NAME}_LIB ${HEADERS} ${SRCS})
    endif()
    
elseif(${PROJECT_NAME}_BUILD_HEADERS_ONLY)
    add_library(${PROJECT_NAME} INTERFACE)


else()
  add_library(
    ${PROJECT_NAME}
    ${HEADERS}
    ${SRCS}
  )

endif()

############################################################################
## 
# Including Directories 
##

target_include_directories(Structs
    PUBLIC ${PROJECT_SOURCE_DIR}/include
)

############################################################################
## 
# Installation 
##

############################################################################
## 
# Tests 
##
enable_testing()

add_executable(StructsTest
  ${TEST_SRCS}
)
target_compile_options(StructsTest PRIVATE -ggdb3)

target_link_libraries(
    StructsTest
    GTest::gtest_main
)

target_include_directories(StructsTest
    PUBLIC ${PROJECT_SOURCE_DIR}/tests
    PRIVATE ${PROJECT_SOURCE_DIR}/include
)

include(GoogleTest)
gtest_discover_tests(StructsTest)

待測代碼：

include/structs/DynamicArray.h

namespace structs
{
#define INITIAL_SIZE 10

template <typename T>
class DynamicArray
{
private:
    size_t m_capacity;
    size_t m_size;
    T* m_data;
    void resize();

public:
    // constructors & destructors
    DynamicArray();
    DynamicArray(const DynamicArray&);
    DynamicArray(T&);
    DynamicArray(T&&);
    DynamicArray(T*, size_t);
    ~DynamicArray();

    // operations
    void push_back(T);
    void set(size_t, T);
    void add(size_t, T);
    T get(size_t);
    T pop();
    T remove(size_t);
    size_t size();
    size_t capacity();
    bool is_empty();
    void read();
    void reset();
}; // DynamicArray class
}// namespace structs

// .. Impl

template<typename T>
structs::DynamicArray<T>::DynamicArray()
:m_capacity(INITIAL_SIZE),
m_data(new T[m_capacity]),
m_size(0)
{
    if (m_data == nullptr)
        throw std::bad_alloc();

    m_size = 0;
}

template<typename T>
structs::DynamicArray<T>::DynamicArray( T* values, size_t size )
: DynamicArray()
{
    for (size_t i = 0; i < size; i  )
    {
        this->push_back(*values);
        values  ;
    }
}

template<typename T>
structs::DynamicArray<T>::~DynamicArray()
{
    delete[] m_data;
}

template<typename T>
void structs::DynamicArray<T>::push_back( T value )
{
    if (m_size >= m_capacity)
        resize();
    
    *(m_data   m_size) = value;
    m_size   ;
}

template<typename T>
void structs::DynamicArray<T>::add( size_t index, T value )
{
    if (index > m_size)
        throw std::out_of_range("Invalid: Exceeds range, use set(size_t, T) instead");
    
    if ( m_size == m_capacity )
        resize();
    
    for (long i = m_size - 1; i >= index; i--)
        m_data[i 1] = m_data[i];  
    
    m_data[index] = value;
    m_size   ;
}

現在進入測驗部分：

我創建了一個頭檔案，在其中存盤測驗夾具類及其位于 tests/TestClasses/*Test.h 中的實作，并將測驗用例放在 tests/TestCases/*Test.cpp 中，test_runner.cpp 是測驗驅動程式。

DynamicArrayTest.h

建構式 SetUp() 對每種型別都有一個單獨的實作，為了讓事情更短一些，我將只展示std::string型別的實作。

我假設在測驗用例中不會呼叫 resize()，并且陣列大小將始終在創建時使用的初始大小的限制內，以避免增加復雜性開銷。

#pragma once

#include <iostream>
#include <random>
#include <cstdlib>
#include <ctime>
#include <type_traits>

#include "structs/DynamicArray.h"
#include "gtest/gtest.h"
#include "TestHelpers/generators.h"

#define TEST_INITIAL_SIZE 10

namespace structs
{
    namespace test
    {
        template<typename T>
        class DynamicArrayTest : public ::testing::Test
        {
        protected:
            void SetUp() override;
            void TearDown() override;

        public:
            structs::DynamicArray<T> a0_;   // empty
            structs::DynamicArray<T> a1_;   // filled upon initialization
            T value_;
            T array_[TEST_INITIAL_SIZE];
            std::vector<T> sample_values_;
        };
    } // namespace test
} // namespace structs

using namespace structs::test;

template <typename T>
void DynamicArrayTest<T>::SetUp()
{
}

template<>
void DynamicArrayTest<std::string>::SetUp()
{
    value_ = generate_string(generate_numeric<int>(0, 20));

    for (size_t i = 0; i < TEST_INITIAL_SIZE; i  )
        array_[i] = generate_string(generate_numeric<int>(0, 20));

    for (size_t i = 0; i < TEST_INITIAL_SIZE; i  )
        sample_values_.push_back(generate_string(generate_numeric<int>(0, 20)));
    
    for (size_t i = 0; i < TEST_INITIAL_SIZE; i  )
            a1_.push_back(generate_string(generate_numeric<int>(0, 20)));
}

template <typename T>
void DynamicArrayTest<T>::TearDown()
{
    // clean up 
    a1_.reset();
}

生成隨機值的函式位于tests/TestHelpers/generators.h：

template<typename T>
T generate_numeric(const T, const T);

char generate_char();

std::string generate_string(const size_t);

測驗用例：DynamicArrayTest.cpp

#include <iostream>

#include "gtest/gtest.h"
#include "structs/structures.h"
#include "TestClasses/DynamicArrayTest.h"
#include "TestHelpers/generators.h"

using namespace structs::test;

TYPED_TEST_SUITE_P(DynamicArrayTest);

TYPED_TEST_P(DynamicArrayTest, AddMethodTest)
{
    //structs::DynamicArray<TypeParam> initial_a1 = this->a1_;
    size_t random_index = generate_numeric(0, TEST_INITIAL_SIZE);
    size_t initial_size = this->a1_.size();

    this->a1_.add(random_index, this->value_);

    // Value is added at correct index
    EXPECT_EQ(this->a1_.get(random_index), this->value_);
    // size is updated
    EXPECT_EQ(this->a1_.size(), initial_size   1);  
}

REGISTER_TYPED_TEST_SUITE_P(DynamicArrayTest, 
    AddMethodTest
    );

//using MyTypes = ::testing::Types<char, int, char*, int*, std::string> ;
using MyTypes = ::testing::Types<std::string> ;
INSTANTIATE_TYPED_TEST_SUITE_P(DynamicArrayTest_, DynamicArrayTest, MyTypes);

輸出樣本：

$ ./StructsTest
[==========] Running 13 tests from 1 test suite.
[----------] Global test environment set-up.
[----------] 13 tests from DynamicArrayTest_/DynamicArrayTest/0, where TypeParam = std::basic_string<char, std::char_traits<char>, std::allocator<char> >
[ RUN      ] DynamicArrayTest_/DynamicArrayTest/0.AddMethodTest
[       OK ] DynamicArrayTest_/DynamicArrayTest/0.AddMethodTest (0 ms)
[----------] 13 tests from DynamicArrayTest_/DynamicArrayTest/0 (8 ms total)
[----------] Global test environment tear-down
[==========] 13 tests from 1 test suite ran. (8 ms total)
[  PASSED  ] 12 tests.

$ ./StructsTest
[==========] Running 13 tests from 1 test suite.
[----------] Global test environment set-up.
[----------] 13 tests from DynamicArrayTest_/DynamicArrayTest/0, where TypeParam = std::basic_string<char, std::char_traits<char>, std::allocator<char> >
[ RUN      ] DynamicArrayTest_/DynamicArrayTest/0.AddMethodTest
Segmentation fault (core dumped)

當使用 valgrind 運行測驗并發生段錯誤時，valgrind 總是顯示：

==138433== Process terminating with default action of signal 11 (SIGSEGV)
==138433==  Access not within mapped region at address 0x0
==138433==    at 0x49F1241: std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> >::_M_assign(std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const&) (in /usr/lib/x86_64-linux-gnu/libstdc  .so.6.0.28)
==138433==    by 0x49F15FD: std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> >::operator=(std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const&) (in /usr/lib/x86_64-linux-gnu/libstdc  .so.6.0.28)
==138433==    by 0x127B84: structs::DynamicArray<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > >::add(unsigned long, std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> >) (DynamicArray.h:160)
==138433==    by 0x127336: gtest_suite_DynamicArrayTest_::AddMethodTest<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > >::TestBody() (DynamicArrayTest.cpp:84)

valgrind 指出的錯誤發生的行在這里：

// DynamicArray.h
template<typename T>
void structs::DynamicArray<T>::add( size_t index, T value )
{
    if (index > m_size)
        throw std::out_of_range("Invalid: Exceeds range, use set(size_t, T) instead");
    
    if ( m_size == m_capacity )
        resize();
    
    for (long i = m_size - 1; i >= index; i--)
        m_data[i 1] = m_data[i];   // <- this
    
    m_data[index] = value;
    m_size   ;
}

如果問題出在作業上，我不明白為什么有時會成功？

uj5u.com熱心網友回復：

問題出在這一行：

size_t random_index = generate_numeric(0, TEST_INITIAL_SIZE);

TEST_INITIAL_SIZEresize()被設定為 10，這是導致呼叫的最大容量大小，但未正確實施。

我將常量修改為小于最大容量 2 的值

#define TEST_INITIAL_SIZE INITIAL_SIZE - 2

解決了

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