有没有办法列出所有共享内存对象的名称？答案

【问题标题】：Is there a way to list names of all shared memory objects?有没有办法列出所有共享内存对象的名称？
【发布时间】：2020-09-24 16:48:04
【问题描述】：

因为可以使用boost的find方法managed_shared_memory访问共享内存对象，比如：

res = segment.find<MyType> ("name");

有没有办法列出某个段中定义的所有共享内存对象的名称？我需要它来调试，但没有找到 boost API。

【问题讨论】：

标签： c++ linux ubuntu boost shared-memory

【解决方案1】：

您可以使用named_begin() 和named_end() 迭代器。

一个小演示，它创建各种随机长度的字符串向量并报告找到的数量：

Live On Coliru

#include <boost/interprocess/managed_mapped_file.hpp>
#include <boost/interprocess/containers/string.hpp>
#include <boost/interprocess/containers/vector.hpp>
#include <boost/container/scoped_allocator.hpp>
#include <iostream>
#include <vector>

namespace bip = boost::interprocess;

using Mem = bip::managed_mapped_file;
template <typename T = void>
using Alloc = boost::container::scoped_allocator_adaptor<
        bip::allocator<T, Mem::segment_manager> >;
using String = boost::container::basic_string<char, std::char_traits<char>, Alloc<char> >;
template <typename T>
using Vector = boost::container::vector<T, Alloc<T> >;

int main() {
    auto mf = Mem(bip::open_or_create, "test.bin", 20ul<<30);
    std::cout << "Named #" << mf.get_segment_manager()->get_num_named_objects() << "\n";

    using Container = Vector<String>;

    for (auto to_create: {"foo", "bar", "qux"}) {
        auto& c = *mf.find_or_construct<Container>(to_create)(mf.get_segment_manager());
        auto n = rand()%10;
        for (int i = 0; i<n; ++i) {
            c.emplace_back(std::to_string(i*i));
        }
    }

    std::cout << "Named #" << mf.get_segment_manager()->get_num_named_objects() << "\n";

    for (auto it = mf.named_begin(); it != mf.named_end(); ++it) {
        std::string_view name(it->name(), it->name_length());
        std::cout << "Item " << name << " has " <<
            reinterpret_cast<Container const*>(it->value())->size() << " elements\n";
    }

}

打印

Named #0
Named #3
Item bar has 6 elements
Item foo has 3 elements
Item qux has 7 elements

当然，我不鼓励使用reinterpret_cast。像往常一样使用find_or_construct 接口。

【讨论】：