c++ - 想知道为什么我会遇到段错误

Question

我有这段代码，我试图根据用户输入的输入“gen”创建许多数据结构。这是代码:

#include <iostream>
#include <algorithm>
#include <string>
#include <iomanip>
#include <limits>
#include <stdio.h>
#include <sstream>


using namespace std;
using std::stringstream;
struct rootset {
  double totSize;
  const char *rStrtPtr;
  const char *rEndPtr;

  struct generations {
    double totSize;
    const char *genStrtPtr;
    const char *genEndPtr; 
    int numOfGen;
    string genName;

    struct object {
      double objSize;
      const char *objStrtPtr;
      const char *objEndPtr;
      string id;
      char markBit;
      char objPtr;


      struct freeList {
    double freeSpace;
    int flNumb; 
      };
    };
  };
};

int main()
{

  int gen =0;
  cin >> gen;
  cin >> pmemSize;

  vector<rootset> pRootSet;
  pRootSet.push_back(rootset());
  pRootSet[0].totSize = pmemSize;

   vector <rootset::generations> generation;
   generation.push_back(rootset::generations());

  for( i=0; i<gen; i++) {
    stringstream out;
    out << i;
   string s = out.str();
   generation[i].genName = "generation" + s
   cout<<"gen name: "<<generation[i].genName<<endl;

  }
}

这段代码正在打印:

3
50
gen name: generation0
Segmentation fault (core dumped)

但在我的输出中我希望它创建:

gen name: generation0
gen name: generation1
gen name: generation2
gen name: generation3

请让我知道我的代码有什么问题

Answer 1

看起来您正在越界访问 generation。在您进入循环时它的大小为 1，因此该循环仅适用于 gen 等于 0 或 1。

vector <rootset::generations> generation;
generation.push_back(rootset::generations()); // size = 1

for( i=0; i<gen; i++) {
  ...
  generation[i].genName = "generation" + s         // what is i?
  cout<<"gen name: "<<generation[i].genName<<endl; //  what is i?