Fragment from the manual (https://westes.github.io/flex/manual/Generated-Scanner.html): "When the scanner receives an end-of-file indication from YY_INPUT, it then checks the yywrap() function. If yywrap() returns false (zero), then it is assumed that the function has gone ahead and set up yyin to point to another input file, and scanning continues. If it returns true (non-zero), then the scanner terminates, returning 0 to its caller. Note that in either case, the start condition remains unchanged; it does not revert to INITIAL."
In short, you're supposed to return 1 in yywrap. Either that or set the "%option noyywrap". regards Piotr Siupa
