Re: R-alpha: Linux floating point fix

Peter Dalgaard BSA (pd@kubism.ku.dk)
17 Nov 1996 22:59:56 +0100


To: Thomas Lumley <thomas@biostat.washington.edu>
Subject: Re: R-alpha: Linux floating point fix
From: Peter Dalgaard BSA <pd@kubism.ku.dk>
Date: 17 Nov 1996 22:59:56 +0100
In-Reply-To: Thomas Lumley's message of Sun, 17 Nov 1996 11:12:43 -0800 (PST)
Message-Id: <x2vib4gz6r.fsf@bush.kubism.ku.dk>

Thomas Lumley <thomas@biostat.washington.edu> writes:

> It appears that R can mysteriously lose its ability to ignore floating 
> point errors (eg log(-1)) when code is dynamically loaded. The 
> survival4 library does this. Possibly the _init code in the loaded 
> library is responsible.  This may explain the conflicting messages about 
> log(-1) under Linux-ELF.

If you can demonstrate this with a simple program, I think it warrants
a post on the linux-gcc list. FPE's should be off once and for all
with the newer libraries. (- and with the older ones, linking with
-lieee should do the trick). I find it more than slightly weird that
something somehow should get the idea of meddling with the FPU control
word. 

Second best would be documentation that the dyn.load actually changes
the FPU-CW, a few well-placed test printouts should do the trick.

Note BTW that an *integer* divide-by-zero generates a non-maskable
SIGFPE. This is not a bug, it's POSIX! You just have to program around
that case.

-- 
   O__  ---- Peter Dalgaard             Blegdamsvej 3  
  c/ /'_ --- Dept. of Biostatistics     2200 Cph. N   
 (*) \(*) -- University of Copenhagen   Denmark      Ph: (+45) 35327918
~~~~~~~~~~ - (p.dalgaard@biostat.ku.dk)             FAX: (+45) 35327907
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