Re: Mystery: Why does yylineno cause backing up tables?

[Hans Aberg]

At 00:41 -0800 2002/01/07, Vern Paxson wrote:
>> Why are the following three lines in the flex source?
>>
>>     if ( do_yylineno )
>>         /* This should really be "maintain_backup_tables = true" */
>>         reject_really_used = true;
>
>Well, I've scrutinized the code a fair bit and I'm embarrassed to say that
>I can't figure out why that comment is there :-(.  It certainly appears
>that yylineno as presently implemented shouldn't require the full backup
>tables.  So one possibility is that the comment reflects bit-rot, coming
>from an earlier time when I had implemented yylineno some other way that
>*did* require the backup tables, but they no longer do.  However, the
>second possiblity is that there's some horrible subtle gotcha that really
>does require the tables, but it won't readily manifest itself.  In general,
>I was loathe to turn on reject_really_used, so I have to imagine that I had
>a good reason for doing so; and I'd also think that if I did manage to
>reimplement things to not require reject_really_used, then I would've
>happily removed the restriction.  But at this point, this is simply
>speculation, alas ...

So what is your hunch, would it be acceptable to simply zip out the
reject_really_used = true requiremenet and see what happens?

  Hans Aberg