Thanks, that seems to get around \x00 -- unfortunately, the same issue then reappears with the values \x80 - \xff … I could special case every single value e.g.
\x00 {return ZERO; }
\x80 { return X80; }
\x81 { return X81; }
:
\xff { return XFF; }
. | \n { return *yytext; }
But seems a bit clumsy. Any thoughts?
> On Mar 30, 2021, at 17:01, Chris verBurg <cheetomons...@gmail.com> wrote:
>
>
> Running bison (first) with -d should produce a bison.tab.h file, that your
> flex input should #include to get the definitions of %token names.
>
> -Chris
>
>
>
>> On Mar 30, 2021, at 1:34 PM, Stephen Taylor <stnh.em...@icloud.com> wrote:
>>
>>
>> That appears to give me an error in lex:
>>
>> %option noyywrap
>>
>>
>> %%
>>
>> \x00 { return ZERO; }
>>
>> .|\n { return *yytext; }
>>
>> %%
>>
>>
>>
>> —
>> Error:
>>
>> flex -8 gmr.l
>> gcc -c lex.yy.c
>> gmr.l: In function ‘yylex’:
>> gmr.l:2:10: error: ‘ZERO’ undeclared (first use in this function); did you
>> mean ‘EIO’?
>> \x00 { return ZERO; }
>> ^~~~
>> EIO
>> gmr.l:2:10: note: each undeclared identifier is reported only once for each
>> function it appears in
>> Makefile:13: recipe for target 'lex.yy.o' failed
>> make: *** [lex.yy.o] Error 1
>>
>>
>> Bison likes it.
>> Tried quoting the \x00 but thats not right it appears.
>>
>>
>>
>>> On Mar 30, 2021, at 16:15, Chris verBurg <cheetomons...@gmail.com> wrote:
>>>
>>>
>>> I don’t know how you’ve set up your flex/bison interface, but I’m guessing
>>> from your quoting that you have flex return each character as a token? Can
>>> you special-case 0 to not have the token value 0? That is, flex does this:
>>>
>>> \x00 { return ZERO; }
>>>
>>> And then in your grammar:
>>>
>>> %token ZERO
>>>
>>> and use ZERO instead of ‘\x00’?
>>>
>>> (Note: typed this on a phone..not 100% sure the syntax is right.)
>>>
>>> -Chris
>>>
>>>
>>>> On Mar 30, 2021, at 12:37 PM, Stephen Taylor via Users list for the GNU
>>>> Bison parser generator <help-bison@gnu.org> wrote:
>>>>
>>>> I am trying to parse binary files and obviously need to write rules that
>>>> include the 8-bit value 0x00 — flex appears to allow me to obtain an 8-bit
>>>> scanner using the -8 option. I seem to be able to use ‘\x01’ to ‘\xFF’ for
>>>> individual terminal symbols in Bison rules. Unfortunately, ‘\x00’ is used
>>>> to denote end of input. Looking at the output tables, there appears to be
>>>> no real reason to do this (other than convenience) and I am wondering if
>>>> anyone has a workaround?
>>>> Thanks !
>>>> Steve
>>>>
>>>>
>>>>
>>>>
>>>
>>
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