c++ ifstream fail() flag is on but no error shown by strerror()

I had code like below. I feel like the file stream didn't reach the file end, because ln_cnt value isn't equal to the feature count (i.e. number of polyline features) shown in QGIS.

Such inequality happend when the shapefile is large so I can't count features one by one, but I used small-sized shapefile for test already and my code works well.

polyline_class line_1;

int ln_cnt ++; // the counter for counting the lines that's read

ifstream reader("some_polyline.shp", ios::in | ios::binary);

while (!reader.eof()){

    shp_read_pnt(&reader, &line_1);
    ln_cnt ++;

}

cout << ".good() = " << reader.good() << "\n";
cout << ".bad() = " << reader.bad()   << "\n";
cout << ".fail() = " << reader.fail() << "\n";
cout << ".eof() = " << reader.eof()   << "\n";
cerr <<  "Error: " << strerror(errno);
reader.close();

The result is :

.good() = 0
.bad() = 0
.fail() = 1
.eof() = 1
Error: No error

Is there an error, actually ?