进程间共享内存的非Boost STL分配器？

#include <iostream>
#include <vector>
#include <sys/mman.h>
#include <fcntl.h>
#include <unistd.h>

template <typename T>
class SharedMemoryAllocator {
public:
    using value_type = T;

    SharedMemoryAllocator(const std::string& name, size_t size)
        : shm_name(name), shm_size(size) {
        shm_fd = shm_open(shm_name.c_str(), O_CREAT | O_RDWR, 0666);
        if (shm_fd == -1) {
            throw std::runtime_error("Failed to open shared memory");
        }
        if (ftruncate(shm_fd, shm_size) == -1) {
            close(shm_fd);
            throw std::runtime_error("Failed to set shared memory size");
        }
        shm_ptr = mmap(nullptr, shm_size, PROT_READ | PROT_WRITE, MAP_SHARED, shm_fd, 0);
        if (shm_ptr == MAP_FAILED) {
            close(shm_fd);
            throw std::runtime_error("Failed to map shared memory");
        }
    }

    ~SharedMemoryAllocator() {
        munmap(shm_ptr, shm_size);
        close(shm_fd);
        shm_unlink(shm_name.c_str());
    }

    T* allocate(size_t n) {
        return static_cast<T*>(::operator new(n * sizeof(T)));
    }

    void deallocate(T* p, size_t n) {
        ::operator delete(p);
    }

private:
    std::string shm_name;
    size_t shm_size;
    int shm_fd;
    void* shm_ptr;
};

int main() {
    const std::string shm_name = "/my_shared_memory";
    const size_t shm_size = 4096;

    SharedMemoryAllocator<int> allocator(shm_name, shm_size);

    std::vector<int, SharedMemoryAllocator<int>> shared_vector(allocator);

    shared_vector.push_back(42);

    std::cout << "Shared vector size: " << shared_vector.size() << std::endl;

    return 0;
}