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
>>>
>>>
>>>
>>>
>>
>
