Question

我正在尝试了解boost进程库的工作原理。我有一个Equipment类，它在向量容器中保存整数值。

在父母进程中; 我在 MySegmentObject 段中构建了Equipment对象，在该对象的构造函数中，我在 MySegmentVector 段中创建了向量。

使用子进程; 我想访问创建的对象并获取向量的大小。我可以使用segment->find方法访问该对象，但是，当我从被访问对象调用getSize()方法时，它会崩溃！

我做错了什么，可能我错过了共享内存概念。

我测试了Visual Studio 2010上的代码＆amp;提升1.43.0 lib

Equipments.h

#pragma once
#include <boost/interprocess/managed_shared_memory.hpp>
#include <boost/interprocess/containers/vector.hpp>
#include <boost/interprocess/allocators/allocator.hpp>

using namespace boost::interprocess;

typedef boost::interprocess::allocator<int, managed_shared_memory::segment_manager>     ShmemAllocator; 
typedef boost::container::vector<int, ShmemAllocator> EqVector;

class Equipments { 
public:     
    Equipments(void);   
    ~Equipments(void);  
    void addEquipment(int n);   
    int getSize();  
    int getElement(int n);

private:
    const ShmemAllocator *alloc_inst;
    <offset_ptr>EqVector eqVector;
    managed_shared_memory *segment;
};

Equipments.cpp

#include "StdAfx.h"
#include "Equipments.h"
#include <iostream>

Equipments::Equipments(void)
{   
    shared_memory_object::remove("mySegmentVector"); 
    segment = new managed_shared_memory(create_only, "mySegmentObjectVector", 65536);
    alloc_inst = new ShmemAllocator(segment->get_segment_manager());
    eqVector = segment->construct<EqVector>("myVector")(*alloc_inst);
}


Equipments::~Equipments(void)
{
}

void Equipments::addEquipment(int n)
{
    eqVector->push_back(n);
}

int Equipments::getSize()
{
    return eqVector->size();
}

int Equipments::getElement(int n)
{
    return eqVector->at(n);
}

Main.cpp的

#include "stdafx.h"
#include "Equipments.h"
#include <iostream>
#include <string>
#include <boost/interprocess/managed_shared_memory.hpp>
#include <boost/interprocess/containers/vector.hpp>
#include <boost/interprocess/allocators/allocator.hpp>

using namespace boost::interprocess;

int main(int argc, char *argv[]) 
{
    if (argc == 1) 
    {
        std::cout << "parent process" << std::endl;
        shared_memory_object::remove("mySegmentObject"); 
        managed_shared_memory segment(create_only, "mySegmentObject", 65536);
        Equipments *eqPtr = segment.construct<Equipments>("EQ")();

        eqPtr->addEquipment(19);
        eqPtr->addEquipment(12);

        //Launch child process
        std::string s(argv[0]); s += " child ";
        if(0 != std::system(s.c_str()))
            return 1;        //Launch child process
    }
    else 
    {
        std::cout << "child process" << std::endl;
        managed_shared_memory *segment = new managed_shared_memory(open_only, "mySegmentObject");
        std::pair<Equipments*, std::size_t> p = segment->find<Equipments>("EQ");

        if (p.first) 
        {
            std::cout << "EQ found" << std::endl;       
       std::cout << p.first->getSize() << std::endl;       
        }
        else 
        {
            std::cout << "EQ not found" << std::endl;
        }
    }
}

Answer 1

问题是您使用普通指针存储EqVector。映射共享内存段时，它可能会映射到进程地址空间中的任何位置。这意味着eqVector存储在内存中的位置在第一个进程的“内存空间”中与第二个进程中的不同。您需要使用boost :: offset_ptr，它将地址存储为共享内存段开头的偏移量，请参见此处：http://www.boost.org/doc/libs/1_35_0/doc/html/interprocess/offset_ptr.html

使用boost进程访问共享对象的向量元素

1 个答案: