无法解引用指向数组的指针，函数返回数组指针后取值错误

核心问题 #

你遇到的是栈内存生命周期非法访问问题，本质错误如下：

• 函数op_calculation中定义的unsigned int local[*(op_size_)]是栈上分配的局部数组，它的生命周期仅存续于op_calculation函数执行期间。
• 你通过*op_ptr_array_ = &local[0]把栈内存地址返回给了上层main函数，当op_calculation执行结束后，对应的栈帧会被操作系统回收，这块内存的内容会被后续执行的其他代码（比如main里的std::cout调用）覆盖，虽然地址还是原来的数值，但指向的内容已经非法无效，所以读出来的值都是错的。
• 额外说明：你写的unsigned int local[*(op_size_)]是C语言的变长数组（VLA）语法，标准C++本身不支持这种写法，只有部分编译器做了扩展支持，这个写法本身不具备可移植性。

修复方案 #

把局部数组的内存分配从栈改成堆，堆内存的生命周期由开发者手动控制，不会随函数退出自动销毁：

1. 把unsigned int local[*(op_size_)];替换成堆分配语句：unsigned int* local = new unsigned int[*(op_size_)];
2. 数组用完后在main函数末尾手动释放堆内存，避免内存泄漏：

delete[] ip_ptr_array;
delete[] op_ptr_array;

修改后完整可运行代码 #

#include <iostream>

void op_calculation(unsigned int*  ip_ptr_array_,
                    unsigned int   ip_size_,
                    unsigned int** op_ptr_array_,
                    unsigned int*  op_size_)
{
    *(op_size_) = ip_size_ + 2;
    std::cout<<"op_size_ address: "<<op_size_<<std::endl;
    std::cout<<"op_size_ value: "<<*(op_size_)<<std::endl;

    // 栈分配改为堆分配，延长内存生命周期
    unsigned int* local = new unsigned int[*(op_size_)];
    std::cout<<"making local array to be pointed by op_ptr_array_\n";
    for (unsigned int i = 0; i< *(op_size_); i++)
    {
        local[i]=i+1*3;
        std::cout<<local[i]<<" ";
    }
    std::cout<<"\n";
    *op_ptr_array_ = &local[0];
    local[3] = 87; // 用于校验指针特性
    for (unsigned int i = 0; i < *(op_size_); i++)
        std::cout<<"array address: "<<&local[i]<<" ,op_ptr_array address: "<<(*op_ptr_array_)+i<<" ,val of array: "<<local[i]<<" ,val at op_ptr_array: "<<*((*op_ptr_array_)+i)<<std::endl;
}

int main()
{
    unsigned int ip_size = 10;
    unsigned int* ip_ptr_array = new unsigned int[ip_size];

    unsigned int op_size;
    unsigned int* op_ptr_array;

    for(unsigned int i = 0; i < ip_size; i++)
    {
        ip_ptr_array[i] = i+2*2;
    }

    op_calculation(ip_ptr_array,
                ip_size,
                &op_ptr_array,
                &op_size);
    
    std::cout<<"Value printing after operation of op_calculation function\n";
    std::cout<<"op_size: "<<op_size<<std::endl;

    std::cout<<"op_ptr_array\n";
    for(unsigned int i = 0; i < op_size; i++)
        std::cout<<"Address: "<<(op_ptr_array+i)<<" , Value: "<<*(op_ptr_array+i)<<"\n";
    std::cout<<"\n";

    // 手动释放堆内存，避免内存泄漏
    delete[] ip_ptr_array;
    delete[] op_ptr_array;
    return 0;
}

内容的提问来源于stack exchange，提问作者karim