CODEWITHSUNDEEP
c++stdvector
Faeralis
Faeralis

Reputation: 97

std::vector does strange thing

I'm working on a function that reads a file, stores every line whose starting with a colon, and removes every dash contained in the string.
Every time this kind of line is found, push_back() is used to store it in a vector.
The problem is that, every time push_back() is used, all the elements in the vector take the value of the last one. I don't understand why it happens. Here's the code :

 string listContent;
 size_t dashPos;
 vector<char*>cTagsList;
 while(!SFHlist.eof())
 {
    getline(SFHlist, listContent);
    if(listContent[0] == ':')
    {
        listContent.erase(0, 1);
        dashPos = listContent.rfind("-", string::npos);
        while(dashPos != string::npos)
        {
            listContent.pop_back();
            dashPos = listContent.rfind("-", string::npos);
        }
        char* c_listContent = (char*)listContent.c_str();
        cTagsList.push_back(c_listContent);
    }
 }

I first thought it was a problem with the end of the file but aborting the searching process before reaching this point gives the same results.

Upvotes: 0

Views: 131

Answers (1)

wonko realtime
wonko realtime

Reputation: 565

the c_str()-method of std::string states:

The pointer returned may be invalidated by further calls to other member functions that modify the object.

If you're allowed to use a std::vector< std::string > instead of the vector of char*, you're fine since there would be always a copy of the std::string listContent pushed into the vector, ie.

std::string listContent;
 size_t dashPos;
 std::vector<std::string>cTagsList;
 while(!SFHlist.eof())
 {
    getline(SFHlist,listContent);
    if(listContent[0]==':')
    {
        listContent.erase(0,1);
        dashPos = listContent.rfind("-",string::npos);
        while(dashPos!=string::npos)
        {
            listContent.pop_back();
            dashPos = listContent.rfind("-",string::npos);
        }
        cTagsList.push_back(listContent);
    }
 }

(I haven't tested it)

Upvotes: 2

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