c++ - 删除指针数组会使调用者的应用程序崩溃

Question

DLL:Visual Studio 2013(VC12)/应用程序:Visual Studio 2010(VC​​10)

我正在创建一个允许客户端访问我们系统的库。然而，当删除从 dll 返回的指针数组时，客户端应用程序似乎崩溃了。删除普通指针(非数组)时，一切似乎都正常。想法？我注意到，当使用 VC12 作为客户端应用程序时，数组被删除了，但是当使用 VC10 时我遇到了崩溃。

所以我的问题是:为什么当从 dll 返回时删除指针数组时客户端应用程序崩溃，如果删除 dll 分配的内存有问题，删除系统不会；也是一个问题吗？

struct IDevice {
    virtual ~IDevice() {}
    char name[64];
};

class Device : public IDevice {
public:
    Device() {}
    ~Device() {}
};

struct ISystem {
    virtual ~IDevice() {}
    virtual Result::Value GetDevices(Collection<IDevice**>* deviceCollection) = 0;
};

class System : public ISystem {
public:
    Result::Value GetDevices(Collection<IDevice**>* deviceCollection) {
        Result::Value result = Result::Success;
        deviceCollection->collectionSize = 1;
        deviceCollection->collection = new IDevice*[1];

        IDevice* device = new Device();
        Utilities::strcpy_safe(device->name, "blackey");
        deviceCollection->collection[0] = device;
        return result;
    }
};

template<typename T>
struct Collection {
    T collection;
    int collectionSize;
};

///////// Main App ///////////

LoginInfo loginInfo;
string ip("192.168.1.2");
string u("admin");
string password("admin");
loginInfo.port = 443;
loginInfo.ssl = true;
strncpy_s(loginInfo.ipAddress, ip.c_str(), sizeof(loginInfo.ipAddress)-1);
strncpy_s(loginInfo.uname, u.c_str(), sizeof(loginInfo.uname)-1);
strncpy_s(loginInfo.password, password.c_str(), sizeof(loginInfo.password)-1);

ISystem* system = nullptr;
// SystemLogin calls into my dll which allocates memory for system OK
Result::Value result = SystemLogin(&loginInfo, &system);

Collection<IDevice**> devices;
// If the line below is uncommented, and the dll is modified to not allocate memory, but instead use this memory
// then below the delete[] devices.collection; works.
//devices.collection = new IDevice*[50];

// Makes a call into the library which populates devices
result = system->GetDevices(&devices);

for (int i = 0; i < devices.collectionSize; i++) {
    // Each item in the array is deleted OK
    delete devices.collection[i];
}

// Deleting this array of pointers crashes (see screenshots) when it's memory was allocated in the dll.
delete[] devices.collection;

// system deletes OK
delete system;

Answer 1

您应该检查客户端应用程序和您的 dll 是否使用相同的设置编译。为了防止此类问题，最好是:

1. 在客户端分配/释放内存
2. 在 dll(服务器)端分配/取消分配内存

我会推荐 #1，但我看到您正在使用 #2。所以你现在应该做的是添加 system->FreeDevices(&devices); 这将释放内存 - 但在你的 dll 中。

[编辑]

引用阅读msdn : https://msdn.microsoft.com/en-us/library/ms235460.aspx

重要的部分是关于可以构建 dll 和客户端应用程序的不同 CRT。这可能会导致您遇到的确切问题:

Also, because each copy of the CRT library has its own heap manager, allocating memory in one CRT library and passing the pointer across a DLL boundary to be freed by a different copy of the CRT library is a potential cause for heap corruption.