C++ 函数返回数组 [英] C++ functions returning arrays

问题描述

我对 C++ 有点陌生.我习惯用 Java 编程.这个特殊的问题给我带来了很大的问题，因为 C++ 在处理数组时不像 Java.在 C++ 中，数组只是指针.

I am sort of new to C++. I am used to programming in Java. This particular problem is causing me great issues, because C++ is not acting like Java when it is dealing with Arrays. In C++, arrays are just pointers.

但是为什么会出现这样的代码:

But why does this code:

#include <iostream>
#define SIZE 3
using namespace std;

void printArray(int*, int);
int * getArray();
int ctr = 0;

int main() {
  int * array = getArray();

  cout << endl << "Verifying 2" << endl;
  for (ctr = 0; ctr < SIZE; ctr++)
    cout << array[ctr] << endl;

  printArray(array, SIZE);
  return 0;
}

int * getArray() {
  int a[] = {1, 2, 3};
  cout << endl << "Verifying 1" << endl;
  for (ctr = 0; ctr < SIZE; ctr++)
    cout << a[ctr] << endl;
  return a;
}

void printArray(int array[], int sizer) {
  cout << endl << "Verifying 3" << endl;
  int ctr = 0;
  for (ctr = 0; ctr < sizer; ctr++) {
    cout << array[ctr] << endl;
  }
}

为验证 2 和验证 3 打印任意值.也许这与数组真正作为指针处理的方式有关.

print out arbitrary values for verify 2 and verify 3. Perhaps this has something to do with the way arrays are really handled as pointers.

推荐答案

因为你的数组是栈分配的.从 Java 迁移到 C++，您必须非常小心对象的生命周期.在 Java 中，所有内容都是堆分配的，并且在没有对它的引用时进行垃圾收集.

Because your array is stack allocated. Moving from Java to C++, you have to be very careful about the lifetime of objects. In Java, everything is heap allocated and is garbage collected when no references to it remain.

然而，在这里，您定义了一个堆栈分配的数组 a，当您退出函数 getArray 时该数组被销毁.这是向量优于普通数组的(许多)原​​因之一——它们为您处理分配和解除分配.

Here however, you define a stack allocated array a, which is destroyed when you exit the function getArray. This is one of the (many) reasons vectors are preferred to plain arrays - they handle allocation and deallocation for you.

#include <vector>

std::vector<int> getArray() 
{
    std::vector<int> a = {1, 2, 3};
    return a;
}

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