在boost.interprocess中从共享内存中memcpy的问题

Question

这让我感到沮丧.我只是想创建一个共享内存缓冲类,它在通过Boost.Interprocess创建的共享内存中使用,我可以在其中读取/存储数据.我写了以下内容来测试功能

#include <boost/interprocess/shared_memory_object.hpp>
#include <boost/interprocess/mapped_region.hpp>
#include <iostream>
using namespace std;
using namespace boost::interprocess;

int main( int argc, char* argv[] ) {
    shared_memory_object::remove( "MyName" );
    // Create a shared memory object
    shared_memory_object shm ( create_only, "MyName", read_write );
    // Set size for the shared memory region
    shm.truncate(1000);
    // Map the whole shared memory in this process
    mapped_region region(shm, read_write);
    // Get pointer to the beginning of the mapped shared memory region
    int* start_ptr;
    start_ptr = static_cast<int*>(region.get_address());

    // Write data into the buffer
    int* write_ptr = start_ptr;
    for( int i= 0; i<10; i++ ) {
        cout << "Write data: " << i << endl;
        memcpy( write_ptr, &i, sizeof(int) );
        write_ptr++;
    }

    // Read data from the buffer
    int* read_ptr = start_ptr;
    int* data;
    for( int i= 0; i<10; i++ ) {
        memcpy( data, read_ptr, sizeof(int) );
        cout << "Read data: " << *data << endl;
        read_ptr++;
    }

    shared_memory_object::remove( "MyName" );
    return 0;
}

当我运行它时,它会将数据写入OK,但memcpy在读取循环中第一次写入段错误.gdb说如下:

程序收到信号EXC_BAD_ACCESS,无法访问内存.原因:地址为KERN_INVALID_ADDRESS:__ memcpy()中的0x0000000000000000 0x00007fffffe007c5

(gdb)在哪里

#c 0x00007fffffe007c5在__memcpy()#1 0x0000000100000e45 in main(argc = 1,argv = 0x7fff5fbff9d0)at try.cpp:36

功能如此简单,我不知道我缺少什么.任何帮助都感激不尽.

Answer 1

data并没有被指出任何事情.(确保正在编译程序并启用所有警告.)看起来它不应该是指针.

第二个循环应该是:

int* read_ptr = start_ptr;
int data;
for( int i= 0; i<10; i++ ) {
    memcpy( &data, read_ptr, sizeof(int) );
    cout << "Read data: " << data << endl;
    read_ptr++;
}