fstream - C++ getline adding space at beginning of string -

this bit of code keeps throwing space in front of strings i'm attempting retrieve.

void texture_manager::loadsheet(std::string filename, std::string textfile) { std::ifstream infofile(textfile);  if (infofile.is_open()) {     std::string line;     while(std::getline(infofile, line ))     {         std::string texturename;         sf::intrect texture;          texture.height = 32; //these dynamic based on text file defines pixel sizes         texture.width = 32;         if(line.find("<name>") != std::string::npos)         {             std::size_t pos1 = line.find("<name>") + 6; //search name of texture             std::size_t pos2 = line.find(";", pos1);             std::size_t namesize = pos1 - pos2;             texturename = line.substr(pos1, namesize);             std::cout << texturename << std::endl;           }     } } 

here's file i'm reading from. i'm trying name , keeps putting space in front of desert , grass.

<collection>tilemapsheet; <ratio>32; <name>desert; <coords>x=0 y=0; <name>grass; <coords>x=32 y=0; 

since pos1 < pos2, result of pos1 - pos2 negative number. since being stored in variable of type size_t, unsigned int, becomes huge positive number.
substr being called large number 2nd parameter. in case, standard says "if string shorter, many characters possible used". think there ambiguity here , different implementations may lead different behavior.

http://www.cplusplus.com/reference/string/string/substr/

let print values of pos1 , pos2 see happening.

        std::size_t pos0 = line.find("<name>");         std::size_t pos1 = line.find("<name>") + 6; //search texture         std::size_t pos2 = line.find(";", pos1);         std::size_t namesize = pos1 - pos2;          std::cout << pos0 << ", " << pos1 << ", " << pos2 << ", " << namesize << std::endl;          texturename = line.substr(pos1, namesize);         std::cout << "texturename: " <<  texturename << std::endl; 

in case, got following values

0, 6, 12, 18446744073709551610 texturename: desert; <coords>x=0 y=0; 0, 6, 11, 18446744073709551611 texturename: grass; <coords>x=32 y=0; 

when tried (pos2 - pos1), got normal expected behavior.

0, 6, 12, 6 texturename: desert 0, 6, 11, 5 texturename: grass