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我有一个分配错误，我得到一个段错误，在读取核心转储时会给出：

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

这是我相信它所指的代码片段。

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;
}

这是检索功能：

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;
    }
}

飞行记录：

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;

飞行地图.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
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2 回答 2

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bt对于回溯是正确的。您可以看到错误从sortedListClass::Retrieve第 167 行开始。回溯中的下一个条目（回溯到 #0）是运算符 ==，这意味着第 167 行的 == 是导致崩溃的原因。

您发布的代码中有几个 == 调用，因此如果您可以编辑您的帖子并指出哪一行是第 167 行，我们可以进一步诊断。

添加行号后更新：

这只是一个猜测，但您可能忘记ptr在程序早期的某个时间点将成员设置为 NULL，因此在第 167-168 行的循环中curr最终指向随机内存位置，从而导致崩溃。也有可能该内存位置的对象已被释放，但ptr尚未更新并指向现在已删除的对象。仔细检查分配新flightRec对象的代码并确保始终ptr正确设置。

于 2011-04-17T05:00:30.690 回答
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您的代码在哪里size声明/定义？

看起来你以某种方式最终被称为 std::basic_stringsize方法。

于 2011-04-17T04:27:40.207 回答