隔离区故障，需要帮助读取堆芯转储

Question

我有一个分配错误，其中我得到一个segfault，当读取核心转储时给出如下:

#0  0xb781eb27 in std::basic_string<char, std::char_traits<char>, std::allocator<char> >::size() const () from /usr/lib/libstdc++.so.6

我认为它指的是这段代码。

bool flightmap::GetNextCity(int& index, int& nextCity){
    bool success = false;
    flightRec tmp, tmp2;
    for (int i = nextCity; (!success) && (i < size); i++)
    {//if Citytmp goes over size, we never found it
        tmp.DestinationCity = GetCityName(i);
        tmp2 = map[index].Retrieve(tmp,success);
    }//end for loop
    if (success)
    {
        nextCity = GetCityNumber(tmp2.DestinationCity);
    }//end if
    return success;
}

下面是检索函数:

flightRec sortedListClass::Retrieve(flightRec& input, bool& success) const{
    nodeptr curr;
    flightRec tmp;
    curr = head;
    if (head == NULL)
    {//If the list is empty
        std::cout << "List empty, operation not preformed" << std::endl;
        success = false;
    }
    /*LINE 167*/ while ((curr!=NULL)&&(!(curr->DestinationCity==input.DestinationCity))) //<- THIS IS LINE 167
    {//Here we first check if curr points to NULL, then we see if DesinationCity and Origin are not yet found.
        curr=curr->ptr;
    }
    if ((curr->DestinationCity==input.DestinationCity))
    {//If we found it, then let's return it...
        tmp.DestinationCity=curr->DestinationCity;
        //tmp.Origin=curr->Origin;
        tmp.flightnumber=curr->flightnumber;
        tmp.cost=curr->cost;
        success = true;
        return tmp;
    }
    else //We didn't and then...damn.
    {
        //std::cout << "Can't find flight to " << input.DestinationCity << std::endl;
        success = false;
    }
}

flightRec:

struct flightRec{
    std::string Origin;
    int flightnumber;
    float cost;
    std::string DestinationCity;
    bool operator <(const flightRec& rhs) const;
    bool operator ==(const flightRec& rhs) const;
    flightRec* ptr;
};
typedef flightRec* nodeptr;

flightMap.h

#ifndef FLIGHTMAP_H
#define FLIGHTMAP_H
#include "sortedListClass.h"
#include "stackClass.h"
#include <fstream>
#include <cstdio>
class flightmap {
public:
    flightmap();
    flightmap(const flightmap& orig);
    virtual ~flightmap();
    void readcities (std::ifstream& in);
    void readflights (std::ifstream& in);
    void display ();
    void isPath (int& in, int& out);
    void MarkVisited (int& index);
    bool IsVisited (int& index);
    void UnvisitAll ();
    bool GetNextCity (int& index, int& nextCity);
    int GetCityNumber(std::string& city);
    std::string GetCityName(int& index);
private:
    int size;
    sortedListClass* map;
    std::string* origin;
    bool* visited;
};
#endif

在gdb中输入bt后，输出如下:

#0  0xb7f4eb27 in std::basic_string<char, std::char_traits<char>, std::allocator<char> >::size() const () from /usr/lib/libstdc++.so.6
#1  0x0804a407 in std::operator==<char> (__lhs=..., __rhs=...) at /usr/lib/gcc/i686-pc-linux-gnu/4.5.2/../../../../include/c++/4.5.2/bits/basic_string.h:2345
#2  0x0804ab32 in sortedListClass::Retrieve (this=0x8053468, input=..., success=@0xbffff0a3) at sortedListClass.cpp:167
#3  0x0804a1ff in flightmap::GetNextCity (this=0xbffff4dc, index=@0xbffff108, nextCity=@0xbffff104) at flightMap.cpp:197
#4  0x08049ba7 in flightmap::isPath (this=0xbffff4dc, in=@0xbffff164, out=@0xbffff160) at flightMap.cpp:110
#5  0x08049314 in FindPath (datafile=..., map=...) at ola6.cpp:51
#6  0x08049190 in main (argc=2, argv=0xbffff5b4) at ola6.cpp:35

Answer 1

bt对于回溯是正确的。你可以看到错误从sortedListClass::Retrieve第167行开始。回溯中的下一个条目(回溯到#0)是用于操作符==的，这意味着第167行上的==是导致崩溃的原因。

在你发布的代码中有一些==调用，所以如果你能编辑你的帖子并指出哪一行是第167行，我们可以进一步诊断。

添加行号后的更新:

这只是一个猜测，但有可能您忘记在程序早期的某个点将ptr成员设置为NULL，因此在第167-168行周围的循环中，curr最终指向随机内存位置，导致崩溃。也有可能那个内存位置的对象已经被释放了，但是ptr没有被更新，并且指向现在被删除的对象。仔细检查你分配新的flightRec对象的代码，并确保你总是正确地设置ptr。

Answer 2

在您的代码中声明/定义size的位置?

看起来你以某种方式结束了std::basic_string size方法的调用