Path: utzoo!utgpu!jarvis.csri.toronto.edu!cs.utexas.edu!tut.cis.ohio-state.edu!pt.cs.cmu.edu!b.gp.cs.cmu.edu!ralf
From: ralf@b.gp.cs.cmu.edu (Ralf Brown)
Newsgroups: comp.sys.ibm.pc
Subject: Re: Environment problems
Keywords: environment
Message-ID: <8371@pt.cs.cmu.edu>
Date: 9 Mar 90 23:53:12 GMT
References: <1990Mar7.073215.23815@agate.berkeley.edu> <16558@orstcs.CS.ORST.EDU> <25F5EB94.8142@maccs.dcss.mcmaster.ca> <1990Mar8.162123.4418@cec1.wustl.edu> <25F7EFC0.10904@maccs.dcss.mcmaster.ca>
Organization: Carnegie-Mellon University, CS/RI
Lines: 34

In article <25F7EFC0.10904@maccs.dcss.mcmaster.ca> cs4g6ag@maccs.dcss.mcmaster.ca (Stephen M. Dunn) writes:
}In article <1990Mar8.162123.4418@cec1.wustl.edu> jcb2647@cec1.wustl.edu (James Christopher Beard) writes:
}$ [...] Another reason to either upgrade (to 4.01) or
}$downgrade (to 3.1) from 3.2.  (Others include the floating-point bug
}$in 3.2 [...]
}
}   What floating-point bug?  DOS doesn't handle floating-point math.

From the Turbo C 1.5 README file:

    DOS 3.2 has a bug in its handling of floating exceptions.  When
    an exception occurs, the system allocates a local stack for the
    exception handler.  Unfortunately, when a system stack gets
    allocated, it never gets deallocated.  The default number of
    stacks is 8.  After 9 floating point exceptions occur, the system
    hangs and a cold reboot is required.  Typical exceptions are
    overflow and divide by zero.  The stacks are not reclaimed when
    a program terminates, so a program which divides by zero once
    will crash the machine if run 9 times.  To avoid this problem,
    you can either:

        1. Not use DOS 3.2.
        2. Obtain a patch from IBM or Microsoft which fixes the
           bug, and install it on your copy of DOS.
        3. Not use a floating point coprocessor.
        4. Disable the exception trapping in your Turbo C program.
           You can do this easily by calling the _clear87() library
           function.  For example,

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