c++ - Seg Fault when creating dynamic array of strings -

my friend writing text-based game , asked me @ code crashing. debugged , getting seg fault when creating dynamic array. i'm not sure why, recommended avoid pointers altogether , use vector solve problem i'm curious going wrong here. here's code:

#include <iostream> #include <fstream> #include <string> #include <cstdlib> #include <ctime>  using namespace std;  class nation {     public:     void init();     string genname();     string getname();      private:     string myname;     int* myborderpoints; };  string nation::getname() {     return myname; }  string nation::genname() {     int listlength = 0, listpos = 0, listrand = 0;     string nametogen = "";     string* namepartlist;     ifstream filename;     filename.open("namepart1.txt");     listlength = filename.tellg();     namepartlist = new string[listlength]; // seg fault here     while (filename.good())     {         while (!filename.eof())         {             getline(filename,namepartlist[listpos]);             listpos += 1;         }     }     listrand = rand() % listlength;     nametogen += namepartlist[listrand];     filename.close();     listlength = 0;     listpos = 0;     listrand = 0;     nametogen = "";     filename.open("namepart2.txt");     listlength = filename.tellg();     namepartlist = new string[listlength];     while (filename.good())     {         while (!filename.eof())         {             getline(filename,namepartlist[listpos]);             listpos += 1;         }     }     listrand = rand() % listlength;     nametogen += namepartlist[listrand];     filename.close();     return nametogen; }  void nation::init() {     srand(time(null));     myname = genname(); }  int main() {     nation testnation;     testnation.init();     cout << testnation.getname();     return 0; } 

you calling tellg:

listlength = filename.tellg(); 

without having read anything, depending on whether file opening or not return 0 or -1 , have called:

namepartlist = new string[listlength] 

with undesirable value. pretty sure returning -1 since allocating 0 sized should ok.

this applies later on code well, going std::vector makes more sense.