SIGSEGV，Segmentation fault

Question

我是C++新手（從我的代碼中可以看出），我正在使用指針和數組以及我的結構練習動態內存分配。我的代碼工作正常，直到它訪問「growArray」函數，然後它給我SIGSEGV錯誤。我不明白爲什麼，因爲據我可以告訴我正確地傳遞一個指針指針，並且我也爲新的指針分配空間。是我的結構的問題，還是傳遞指針的問題，還是接收指針的問題？我希望這個問題是有道理的。

#include <iostream> 
#include <string> 

using namespace std; 

struct FriendInfo 
{ 
    string name; 
    string address; 
    string number; 
}; 

FriendInfo *growArray(FriendInfo *p_entry, int *size); 

int main() 
{ 
    int curNum = 0; 
    int size = 2; 
    int userAnswer; 
    FriendInfo *p_friends = new FriendInfo[size]; 

    cout << "Enter a friend's info?(1 for yes, 0 for no)\n"; 
    cin >> userAnswer; 
    while (userAnswer != 0) 
    { 
     if (curNum == size) 
     { 
      p_friends = growArray (p_friends, &size); 
     } 
     cout << "What is your friend's name?\n"; 
     cin >> p_friends[curNum].name; 
     cout << "What is your friend's address?\n"; 
     cin >> p_friends[curNum].address; 
     cout << "What is your friend's number?\n"; 
     cin >> p_friends[curNum].number; 
     curNum++; 
     cout << "Enter another friend? (1 for yes, 0 for no)\n"; 
     cin >> userAnswer; 
    } 
} 

FriendInfo *growArray(FriendInfo *p_entry, int *size) 
{ 
    *size *= 2; 
    FriendInfo *p_new_friends = new FriendInfo[*size]; 
    for (int i = 0; i < *size; ++i) 
    { 
     p_new_friends[i] = p_entry[i]; 
    } 
    delete [] p_entry; 
    return p_new_friends; 
} 

Answer 1

你的問題是，你要加倍的size價值，即使p_entry是初始size的。代碼更新到這一點：

FriendInfo *growArray(FriendInfo *p_entry, int *size) 
{ 
    int newSize = *size * 2; 
    FriendInfo *p_new_friends = new FriendInfo[newSize]; 
    for (int i = 0; i < *size; ++i) 
    { 
     p_new_friends[i] = p_entry[i]; 
    } 
    delete [] p_entry; 
    *size = newSize; 
    return p_new_friends; 
} 

Answer 2

在你的循環，你想停下來，一旦你已經達到p_entry的大小，而不是大小

FriendInfo *growArray(FriendInfo *p_entry, int *size) 
{ 
    int orig_size = *size; 
    *size *= 2; 
    FriendInfo *p_new_friends = new FriendInfo[*size]; 
    for (int i = 0; i < orig_size; ++i) 
    { 
     p_new_friends[i] = p_entry[i]; 
    } 
    delete [] p_entry; 
    return p_new_friends; 
}