visual c++ - strlen not counting newlines? -

i embedded lua project , came across strange (for me) behavior of strlen , lua interpreting. trying load string, containing lua code, lual_loadbuffer , consistently threw error of "unexpected symbol" on whatever last line of lua code, except if whole chunk written in 1 line. example:

  function start()       print("start")   end 

would results error: unexpected symbol on 3rd line, but

function start() print("start") end 

loads successfully.

i figured out loading same chunk lual_loadstring, gives no errors, , saw uses strlen determine length of specified string (i used std::string::size) , using strlen provide length of string lual_loadbuffer results in successful loading.

now question was: may difference between strlen , std::string::size, , @ surprise answer strlen not counting new lines ('\n'). is:

 const char* str  = "this string\nthis newline";   std::string str2(str);   str2.size(); // gives 34   strlen(str); // gives 33 

the difference between size, , value returned strlen number of new line characters.

my questions are:

1. does strlen not counting newlines or missing something?
2. how newlines affect interpretation of lua code internally?

i using vs 2015 , lua 5.3.0

edit:

my first example not exact, , did not produce detailed effect me neither, able recreate problem original code:

std::fstream _stream("test.lua", std::ios::ate | std::ios::in);     std::string _source;     if(_stream.is_open()) {         _source.resize(_stream.tellg());         _stream.seekg(0, std::ios::beg);         _stream.read(&_source[0], _source.size());         _stream.close();     }      std::cout << "std::string::size() = " << _source.size() << std::endl;     std::cout << "strlen() = " << strlen(_source.c_str()) << std::endl; 

the content of test.lua "function start()\n\tprint("start")\nend\n\nstart()"

the difference number of newlines:

http://i.stack.imgur.com/y0qow.png

window's line endings (cr+lf) 2 characters making file size larger number of characters in string resize operation uses file size , not length of null-terminated string. strlen reports length of null-terminated string , counts \n single character. can make size match length of c string resizing string match afterwards:

_source.resize(strlen(_source.c_str()) + 1);