Re: Divide by 0 - exception thrown?

From:

"Carl Daniel [VC++ MVP]" <cpdaniel_remove_this_and_nospam@mvps.org.nospam>

Newsgroups:

microsoft.public.vc.language

Date:

Tue, 17 Oct 2006 19:54:00 -0700

Message-ID:

<eY7OrCm8GHA.4552@TK2MSFTNGP05.phx.gbl>

David Wilkinson wrote:

Jason Doucette wrote:

2. Could be this only happened when I printed from my own
application; I don't remember.

Quoted from: http://www.codeguru.com/forum/showthread.php?p=1473151

"...any code that relies on third-party software, i.e. loading of
drivers, then there is your risk of having the FPU control word
change on you. The HP printer drivers from some time back were
notorious for changing the state of the FPU control word whenever
they were used." This was likely the issue, David.
Can you confirm this?

Jason:

I just use the printing capability provided by MFC-docview. Presumably
this activates the driver of the selected printer.

Correct.

Be aware: we're using the term "driver" loosely here. There are
kernel-mode Drivers (files that end in .SYS usually), and then there are
various kinds of user-mode plug-ins to support hardware that are sometimes
referred to as drivers. Kernel mode drivers will NEVER corrupt your FP
state - the OS makes sure that can't happen. User-mode drivers, however,
run in the context of user-mode threads - sometimes that means your thread!

Printers in particular have large and complex user-mode drivers and
frequently don't include any kernel-mode device driver components at all.
These "drivers" run partially or entirely in the context of the thread that
initiated the printing operation. If some part of a user mode driver that
runs in your thread changes the FP control word, then you'll experience the
trouble documented in the CodeGuru article.

-cd