返回時的分段錯誤int

Question

下面我有兩個函數，當insertItem調用findIndex時會產生分段錯誤。出於某種原因，返回值時會發生這種情況。 （我將包括cout語句，以便很容易地看到發生此錯誤的確切位置）。我試圖找到不在列表中的值的索引，因此-1應該被返回，但從來沒有。輸出如下。

template <class ItemType> 
int SortedList<ItemType>::findIndex(ItemType item) { 
    cout << "Entering findIndex function" << endl; 
    int first = 0; 
    int last = length-1; 
    int middle; 
    bool found = false; 
    while(!found) { 
    middle = (first+last)/2; 
    cout << "In findIndex, this is middle: " << middle << " and this is  the item: " << item << " and this is the length: " << length << endl; 
    if(info[middle] == item) { 
     cout << "In findIndex found is now true" << endl; 
     found = true; 
    } 
    else if(item < info[middle]) 
     last = middle-1; 
    else// if(item > info[middle])                                     
     first = middle+1; 
    if(first > last)//else// if(first > last)                                   
     break; 
    } 
    cout << "About to exit and return value from findIndex function" << endl; 

    if(found == true) { 
    cout << "findIndex Function: the index of the found value was " <<  middle << endl; 
    return middle; 
    } 
else { 
    cout << "findindex Function: -1 was returned" << endl; 
    return -1; 
    } 
} 




template <class ItemType> 
void SortedList<ItemType>::insertItem(ItemType item) { 
    cout << "Inside insertItem function, length: " << length << endl; 
    if(findIndex(item) != -1) 
    cout << "**Item already in the list" << endl; 
    else if(length == Max_Items) 
    cout << "**There is no room in the list" << endl; 
    else { 
    cout << "before the try" << endl; 
    try{ 
     cout << "This is length at the start of the insertItem function: " << length << endl; 
     if(length == 0) {//if the list is empty item becomes the first item in the list                        \ 

     cout << "This is right after length==0 in insertItem function" << endl; 
     info[0] = item;//was this->inf...                                    
     length++; 
     cout << "This is length right after incrementing it up" << length << endl; 
     } 
     else {//its not the first item in the list                                  
     for(int i = 0; i <= length; i++) { 
      cout << "This is the length and i respectively right inside the for in insertItem" << length << " " << i << endl; 
      if(i == length) { 
      cout << "this is where i == length" << endl; 
      info[i] = item; 
      length++; 
      break; 
      } 

      if(info[i] < item) 
      continue; 
      //inserting the item where it needs to go                                 
      for(int p = length; p > i; p--) {//was >=                                 
      info[p] = info[p-1]; 
      } 
      //item = info[i];                                       
      info[i] = item; 
      length++; 
      break; 
     } 
     } 
    }catch(...) {cout << "**insertItem failed" << endl;} 
    } 
    cout << "This is length at the end of the insert item function: " <<  length << endl; 
} 

輸出： ... 內部insertItem功能，長度：0

輸入findIndex功能

在findIndex，這是中間位置：0，這是該項目：名稱：林二汶ID ：81012，這是長度：0

從findIndex函數關於退出和返回值

findindex功能：-1返回

分割故障（核心轉儲）

〜$：

說着-1返回即使打印被擊中，但從來都沒有變回原來的功能。我不確定在這個區域會發生什麼可能導致seg故障。這個回報能做到嗎？

Answer 1

以下循環：

for(int p = length; p > i; p--) { 
    info[p] = info[p-1]; 

大概寫入1個索引經過陣列的長度，因爲有效陣列索引可能範圍從0到length - 1。

寫入非法內存位置可能會損壞堆棧，並且這很可能在從函數返回時顯示爲崩潰。

仍然，你真的需要開始使用調試器。