如何在C ++中跨多个进程使用共享向量

Question

我在进程之间共享向量时遇到问题。我可以共享矢量，甚至可以从不同的过程中获得矢量的大小，但是当我在函数中使用时，程序会崩溃。

    struct B
   {
      std::vector<int> vec;
   };

    int main(int cArgs, char* ppszArgs[])
   {
       if (cArgs == 1) {  //Parent process
          //Remove shared memory on construction and destruction
       struct shm_remove
        {
        shm_remove() { shared_memory_object::remove("MySharedMemory"); }
        ~shm_remove() { shared_memory_object::remove("MySharedMemory"); }
       } remover;

    //Create a shared memory object.
    shared_memory_object shm(create_only, "MySharedMemory", read_write);

    //Set size
    shm.truncate(1000);

    //Map the whole shared memory in this process
    mapped_region region(shm, read_write);

    //Write all the memory to 1
    B* test = new B();


    CopyMemory(region.get_address(), test, sizeof(B));


    parentProcess(); -> this method just starts the child process

    int index = 1;
    while (true)
    {
        if(index < 2)
        {
            ((B*)region.get_address())->vec.push_back(index);
        }
        ++index;
    }

}
else
{
    //Open already created shared memory object.
    shared_memory_object shm(open_only, "MySharedMemory", read_only);

    //Map the whole shared memory in this process
    mapped_region region(shm, read_only);

    //Check that memory was initialized to 1
    HANDLE mem = region.get_address();


    while(true)
    {
        std::cout << ((B*)mem)->vec.at(0) << std::endl; -> if for example i put 
        lista.size(), then i will get the number of items in vector.
    }

}

}

我的问题甚至可以从子进程访问矢量元素吗？

Answer 1

要共享数据，您需要使用共享内存机制（对于Linux和CreateFileMapping为PC共享内存，对于Windows为MapViewOfFile，...），但这不允许您共享诸如矢量之类的复杂对象。

想象P1进程创建一个向量并存储一些元素。

Vector_P1 <element1, element2, element3, ...>  

element1, element2, element3已在P1（P1的堆）的地址空间中创建，我们假设：

• element1 ==>地址= 0xAB123456
• element2 ==>地址= 0xCD123456
• element3 ==>地址= 0xDE123456

[将向量作为对象共享时，P2进程将使用不属于其地址空间的地址0xAB123456, 0xCD123456, 0xDE123456，这将导致memory access violation

您只能共享的是PODS类型。一旦传递了new保留的复杂对象，它将无法正常工作