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From:	Nick Bowler <nbowler AT draconx DOT ca>
Newsgroups:	comp.os.msdos.djgpp
Subject:	Reading /dev/null seems broken.
Date:	Tue, 15 Jan 2013 04:18:07 +0000 (UTC)
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To:	djgpp AT delorie DOT com
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Reply-To:	djgpp AT delorie DOT com

Hi folks,

I've been playing around with DJGPP in dosemu, trying to build one of my
own C projects using the GNU build system (autoconf, automake, etc.)  I
installed the latest versions from the "current" directory on the DJGPP
FTP site.

After some minor configuration struggles, the configure script mostly
worked, until it came time to run config.status (a shell script which gets
generated and run by the main configure script).  At this point, the entire
system would (apparently) lock up.  I tracked this down to one line in the
script which reads from /dev/null, which looks like this:

  if sed "s/$ac_cr//" < /dev/null > /dev/null 2>&1; then

Sure enough, the lockup can easily be reproduced from the DJGPP bash
prompt with a similar command:

  sed 's/x//' < /dev/null > /dev/null

which hangs in the same way.  If I omit the >/dev/null redirection, then
endless garbage data is spewed to the console instead of the expected
nothing at all.

On a "real" POSIX-y system, this should exit with success since reading
from /dev/null will always return 0 (EOF).  I replaced the entire test
with a simple "true" in the config.status script, and things ran fine.
Another instance came up later during the build, with a command similar
to:

  cat /dev/null > file

This is expected to produce an empty output file, but instead, gigabytes
of garbage are written.  Seems to be pretty much the same root problem.

While in this case I can work around these problems, should DJGPP be
presenting a /dev/null that works properly?

Cheers,
  Nick

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