7bit switch doesn't work but 8bit and unicode does

[vinhtq115]

I'm trying to generate a specification for a language using 7bit switch but JFlex won't generate anything. It always says:

Reading "vc.flex"
0 errors, 0 warnings.

Generation aborted.

When I use 8bit or unicode switch, it works fine.

Reading "vc.flex"
Constructing NFA : 276 states in NFA
Converting NFA to DFA :
...............................................................................
.......................................................
138 states before minimization, 121 states in minimized DFA
Writing code to "Scanner.java"
0 errors, 0 warnings.

Generation finished successfully.

I'm using JFlex 1.8.1.

[lsf37]

Hi @vinhtq115, thanks for the report. Could you append the lex spec or a shortened version of it that has the same symptom?

[vinhtq115]

Hi @vinhtq115, thanks for the report. Could you append the lex spec or a shortened version of it that has the same symptom?

Here you go:

vc.flex.txt
(Please remove txt extension)

[lsf37]

Thanks for that, I can reproduce the problem and confirm this is a bug. Will look into it.

For now, I'd recommend using %unicode (or nothing, since unicode is default) instead. I don't know if that is the case for your setting, but often, even if correct input is only 7 or 8 bit, incorrect input could still contain other characters. If that happens in the 7 or 8 bit scanner, you'll get an exception that you need to handle outside the scanner, whereas in the unicode scanner, you can write a default rule for unmatched characters that deal with the error case inside the scanner spec.