Path: utzoo!mnetor!uunet!husc6!ncar!ames!pacbell!att-ih!alberta!edson!tic!dragos!work
From: work@dragos.UUCP (Dragos Ruiu)
Newsgroups: comp.unix.microport
Subject: Re: YAMB: problems with yacc?
Message-ID: <397@dragos.UUCP>
Date: 22 Mar 88 02:44:29 GMT
References: <437@splut.UUCP>
Organization: UNIX Device
Lines: 36
Keywords: won't do hoc1 right
Summary: Confirm Yacc Problem

In article <437@splut.UUCP>, jay@splut.UUCP (Jay Maynard) writes:
> I tried entering the program hoc1, from the book _The Unix Programming
> Environment_, and compiling it last night. It doesn't run: when fed an
> expression like 2+2, instead of printing 4, it prints 2. It appears to
> reproduce productions of the form:
> expr: expr '+' expr { $$ = $1 + $3 }...
> by simply returning $3, instead of computing the sum. I have checked the
> program against the printed source in the book twice, and found no
> errors. Neither yacc nor cc complain during compilation of the program.

> Vitals: System V/AT (286) 2.3.0, plenty of (hard and ram-) disk.
> 
> -- 
> Jay Maynard, EMT-P, K5ZC...>splut!< | GEnie: JAYMAYNARD  CI$: 71036,1603
> uucp: {uunet!nuchat,academ!uhnix1,{ihnp4,bellcore,killer}!tness1}!splut!jay

 I also encountered the bug in yacc. It seems to be in the add/sub/mult/div
 of two floating point numbers. I spent a bit of time looking over this
 problem... but I eventually discarded my work and tried the desc calculator
 program I wrote on BSD and HP-UX systems and they worked there.

 I can dig up the sources in a day, but if my memory serves me correctly,
 it's not a Yacc problem... I believe it was a bug in the c compiler as I
 went and actually debugged the yacc output. There is a large set of
 indirection and structure references produced by yacc, and printfs on the
 intermediate results and actual results just don't match. Unfortunately
 I don't have time to track down this bug anymore.
 
 I can email the sources which produce bugs to interested parties. Or if
 enough people are interested I can post them. They aren't long.

-- 
Dragos Ruiu   ruiu@dragos.UUCP
              ...alberta!dragos!ruiu	  OS/2... No thanks I have a pencil.

Disclaimer: These are my employers opinions. I'm unemployed.