自定义vector模板类扩容崩溃（错误码0XC0000005）求助

Hey there! That error code 0XC0000005 is a classic access violation—your program’s trying to read or write memory it doesn’t own, which lines up perfectly with it crashing mid-expansion of your custom vector. Let’s walk through the most likely issues and how to fix them:

Common Culprits & Fixes #

1. Broken Resize/Copy Logic #

This is the #1 cause of crashes in custom dynamic arrays. When you expand the array, you might be:

• Copying too many elements (using new capacity instead of current size)
• Forgetting to update capacity after resizing
• Mishandling initial capacity (e.g., starting with capacity = 0 and trying to write to data[0] before first resize)

Here’s a corrected example of a reserve function:

template<typename T>
void MyVector<T>::reserve(size_t new_cap) {
    if (new_cap <= m_capacity) return;

    // Allocate new memory
    T* new_data = new T[new_cap];

    // Copy ONLY the current number of elements (m_size, not new_cap!)
    for (size_t i = 0; i < m_size; ++i) {
        new_data[i] = m_data[i];
    }

    // Clean up old memory and update pointers
    delete[] m_data;
    m_data = new_data;
    m_capacity = new_cap;
}

Pro tip: Avoid memcpy for non-POD structs (structs with pointers, strings, or custom constructors)—it does a shallow copy, which leads to double-free errors or dangling pointers. Use element-wise assignment instead.

2. Timing of Resize Checks #

Make sure you always check if you need to resize before adding a new element. A faulty push_back might try to write to data[m_size] when m_size == m_capacity:

template<typename T>
void MyVector<T>::push_back(const T& value) {
    // Resize first if we're at capacity (handle 0 initial capacity!)
    if (m_size == m_capacity) {
        reserve(m_capacity == 0 ? 4 : m_capacity * 2);
    }
    m_data[m_size++] = value;
}

3. Struct Copy Issues #

If your struct contains dynamic memory (like char* or another custom container), your vector’s default element assignment will do a shallow copy. This means two elements end up pointing to the same memory, leading to crashes when one is destroyed or modified.

Fix this by adding a copy constructor and copy assignment operator to your struct, ensuring deep copies of any dynamic members.

4. File Reading Glitches #

It’s possible the crash isn’t the vector’s fault at all—maybe your file reading code is corrupting the struct data at line 5121. Add debug prints to log each struct’s values as you read them; if you see garbage values (e.g., invalid pointers, huge numbers), fix the reading logic first.

5. Dangling Pointers After Deletion #

When you delete the old array in reserve, make sure you don’t leave any references to the old m_data pointer. And never delete m_data more than once (a common mistake if you don’t null it out after deletion, though modern compilers help with this).

Quick Test to Isolate the Problem #

First, test your vector with a simple type like int:

MyVector<int> vec;
for (int i = 0; i < 100000; ++i) {
    vec.push_back(i);
}

If this runs without crashing, the issue is specific to your struct or file reading code. If it still crashes, your vector’s core logic has a bug.

内容的提问来源于stack exchange，提问作者Jason Collier