[ ghc-Bugs-537295 ] div 0 0 give exception / endless loop

Bugs item #537295, was opened at 2002-03-31 01:36
Message generated for change (Comment added) made by snailtalk
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Category: Runtime System
Group: 5.02
>Status: Open
>Resolution: Remind
Priority: 5
Submitted By: geoff (snailtalk)
Assigned to: Simon Marlow (simonmar)
Summary: div 0 0 give exception / endless loop

Initial Comment:
There is a problem with the div in ghc, to reproduce:

start ghci and type div n 0 where n is any integer (so
div 3 0 would work)

on a linux box it gives a floating point exception
while on a BSD 4.4 box it gives and endless loop using
about 87 % of cpu.

I have verified this on both the latest release
(5.02.2) and 5.02.1.



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>Comment By: geoff (snailtalk)
Date: 2003-04-23 19:07

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It has come to my attention that it is still not fixed in
5.04.2 (my fault for not reading the exact nature of the
fix).  I assume because for SIGFPE in Unix, the result is
undefined after return from the signal handler.

Here is some sample code to demonstrate:

usage: signal (+|-)u (signal|sigaction)

options:
+u  : uninstall signal in sighandler
-u   : don't uninstall signal in sighandler
signal:  install using signal()
sigaction:  install using sigaction()
 
so for example, signal +u sigaction would install the
handler using sigaction and uninstall the signal in the
signal handler.  The signal is hardcoded to SIGFPE.


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Comment By: Simon Marlow (simonmar)
Date: 2002-07-02 11:30

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Fixed by not ignoring SIGFPE.

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