[1346] in linux-announce channel archive
IMPORTANT: WARNING ABOUT g77-0.5.16!!!
daemon@ATHENA.MIT.EDU (Lars Wirzenius)
Fri Nov 24 18:41:01 1995
Date: Thu, 23 Nov 1995 22:27:16 +0200
From: Lars Wirzenius <wirzeniu@cc.helsinki.fi>
To: linux-announce@vger.rutgers.edu
From: burley@cygnus.com (Craig Burley)
Newsgroups: comp.os.linux.announce
Subject: IMPORTANT: WARNING ABOUT g77-0.5.16!!!
Organization: Free Software Foundation 545 Tech Square Cambridge, MA 02139
References: <48fp3b$16s@hecate.umd.edu>
In-Reply-To: jf95@umail.umd.edu's message of 16 Nov 1995 16:32:43 GMT
Approved: linux-announce@news.ornl.gov (Lars Wirzenius)
Followup-to: comp.os.linux.misc
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[Was Re: g77 and large arrays and segmentation faults]
In article <48fp3b$16s@hecate.umd.edu> jf95@umail.umd.edu (Jeff Forbes) writes:
This is a followup to my previous inquiry about segmentation faults with
large arrays and f2c/gcc. I obtained g77 and it does compile my program with
large arrays and the executable usually runs without segmentation faults.
A couple of times (when other large programs were running) it loaded and
immediately gave seg-fault. OK, now for the weirdness. When I ran top after
this happened, it cleared the screen and then the prompt reappeared.
Additionally, the echo was turned off. Switching to a different xterm or
virtual terminal brings the echo back, but top then gives the same result.
Rebooting Linux does not correct the problem and the top binary is not
corrupted. Does anyone know what the problem might be?
A serious bug in g77-0.5.16 (ONLY) has been reported to me that I am
very sorry about, and which 0.5.17 fixes, and which might cause all
sorts of weird behaviors.
The bug is this:
When using the "g77 -v" command while logged in as `root' (or some
equally powerful user), the file name "/dev/null" is REMOVED from
the system.
The reason is that "g77 -v" is implemented, in 0.5.16, by a command
which ultimates in "ld -o /dev/null ...", and because this command
(intentionally) results in ld complaining about unresolved references,
ld apparently decides to REMOVE the executable it was asked to create
(which is /dev/null).
And, when logged in as root, removing /dev/null actually WORKS!!
After doing this the first time, any command or shell script that
writes to /dev/null will actually write stuff there as a normal file,
and then anything that reads from /dev/null expecting to find an EOF
will NOT find one! Instead it'll find whatever stuff happens to be
sitting there at the time.
To see if this has happened on your Linux system:
cd /dev
ls -l null zero
The entries for these two names should look basically the same, except
the "magic numbers" for `null' should be "1,3" while for `zero' they
should be "1,5".
IF `null' IS MISSING OR IS NOT A "crw-rw-rw- ... 1, 3" FILE (almost
exactly like the entry for `zero'), THEN YOUR `/dev/null' HAS BEEN
CORRUPTED (probably by doing "g77 -v" as user `root'), AND THIS IS WHAT
I THINK YOU SHOULD DO (but please sanity-check it, as obviously I'm
NOT an expert on UNIX sysadmin stuff):
(login as `root')
rm -f null
mknod null c 1 3
chmod 666 null
chgrp sys null
(The chgrp command might not be necessary, or maybe you should change
it so `null' and `zero' have identical user/group ownership as reported
by "ls -l".)
Until g77-0.5.17 is released, which fixes this bug, DO NOT USE "g77 -v"
WHILE LOGGED IN AS `root'!!!
After you fix this problem on your system, retry other things that seem
to behave strangely. If they still do behave strangely, that probably
means you have other problems....
I am really sorry for this bug!
- --
James Craig Burley, Software Craftsperson burley@gnu.ai.mit.edu
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