Issues with writing to a file in c++ -

as part of parsing file, task involves stripping off comments in file , parsing file. once parsing completed, need insert comments @ same lines.

to strip of comments, read file , check if comment has occured , enter newline there. use ragel this, , logic works fine.

example: file.cpp     #1 /** comments */   #2 /** comments */   #3    #4 abcd : xyz, 123   #5 efgh : abc, 987  intermediate_file.cpp  #1   #2   #3   #4 abcd : xyz, 123  #5 efgh : abc, 987 

the comments stored line numbers in std::map<int,string> , used later iterate , output string file, intermediate_file.cpp. using below code same:

fstream m_fstr; //class member std::map<int,std::string> m_comments_map; //to hold comments  void writebackcommentstofile(void) {   m_fstr.open("intermediate_file.cpp", ios_base::out);   int linenbr = 0;   for(std::map<int,std::string>::iterator = m_comments_map.begin(); != m_comments_map.end(); ++it)    {       linenbr = it->first;       if(m_fstr.is_open()) {         m_fstr.seekg(std::ios::beg);         gotoline(m_fstr,linenbr );         m_fstr << it->second << endl;       }   } }  std::fstream& gotoline(std::fstream& file, unsigned int num){     for(int i=0; < num - 1; ++i){         file.ignore(std::numeric_limits<std::streamsize>::max(),'\n');         //getline(m_fstr,readline); -- try     }     return file; } 

after parsing complete, trying write comments m_comments_map file intermediate_file.cpp above logic, able print first line in file - /** comments */ . rest of contents not written file.

i have tried printing out contents of std::map console , verified comments stored in std::map. problem lies in printing out std::map contents file. can tell me part of code incorrect.?

i have implemented above using logic described here : in c++ there way go specific line in text file?