Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!tut.cis.ohio-state.edu!rutgers!orstcs!statware!scf
From: scf@statware.UUCP (Steve Fullerton)
Newsgroups: comp.sys.hp
Subject: Re: buggy hp9000/800 3.01 code?
Keywords: hp,unix
Message-ID: <1876@statware.UUCP>
Date: 30 Mar 89 16:59:40 GMT
References: <659@kcdev.UUCP>
Reply-To: scf@statware.UUCP (Steve Fullerton)
Organization: Statware, Corvallis, Oregon
Lines: 42

In article <659@kcdev.UUCP> gentry@kcdev.UUCP (Art Gentry) writes:
>A few words to the wise on possible nasty bugs in the 3.01 release of 
>HP9000/850 UNIX.

I have encountered another curious problem, anomaly, bug, with the
HP-UX 3.0 release.  Our code for doing raw input that worked fine
under HP-UX 2.0 (as well as about 20 other UN*X systems) now fails
under 3.0.  At first the 2.0x executable failed (I'll explain below)
when run under 3.0.  Next, we tried linking under 3.0 and got the same
failure.  Finally, re-compiling and linking yielded the same result.

What we are doing is setting termio to raw and reading characters 1 at
a time.  It works fine until a cursor key is pressed and then the 2nd
character gets hung in the buffer until the next read...very strange.
We are doing blocked reads so what happens is:

  1) Issue the read
  2) User enters a character, it is read and all is fine, go to 1)
  3) User enters a cursor key so the read returns an ESC, issue another read
  4) This second read blocks waiting for input.  When a key is
     pressed, the second character from the cursor key is what
     is read.
  5) Subsequent reads remain out-of-sync; i.e., when a character is
     entered, the previous entry is what is read.

The code we are using for raw input was extracted directly from Marc Roshkind's
"Advanced UNIX Programming".  Specifically, pages 88-89.  He suggests
termio.c_cc[VMIN] = 5 and termio.c_cc[VTIME] = 2.  I wasn't sure whether
or not the bug was related to VMIN and VTIME or else ICANON.  I was
finally able to get it to work by setting the VMIN value to 1 and the
VTIME value to 0.

I am confident in the code---it has been ported to all major UN*X systems
and even worked fine for HP-UX 2.0x as well as on HP9000/3xx 6.x systems.
So something is really wrong and programs doing screen handling might
have a big surprise when moving to 3.0.

-- 
Steve Fullerton                        Statware, Inc.
scf%statware.uucp@cs.orst.edu          260 SW Madison Ave, Suite 109
orstcs!statware!scf                    Corvallis, OR  97333
                                       503/753-5382