2014-11-24 57 views
0

我是C++新手(从我的代码中可以看出),我正在使用指针和数组以及我的结构练习动态内存分配。我的代码工作正常,直到它访问“growArray”函数,然后它给我SIGSEGV错误。我不明白为什么,因为据我可以告诉我正确地传递一个指针指针,并且我也为新的指针分配空间。是我的结构的问题,还是传递指针的问题,还是接收指针的问题?我希望这个问题是有道理的。SIGSEGV,Segmentation fault

#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; 
} 
+0

强制性的问题 - 你为什么不使用是'的std :: VECTOR'? – PaulMcKenzie 2014-11-24 17:37:41

+2

@PaulMcKenzie:因为他正在训练如何驾驶手动? – Deduplicator 2014-11-24 17:39:02

+0

他明确表示他在练习DMA :) – 2014-11-24 17:46:10

回答

3

你的问题是,你要加倍的size价值,即使p_entry是初始size的。代码更新到这一点:

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; 
} 
0

在你的循环,你想停下来,一旦你已经达到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; 
} 
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