R help - Jan 2001 - dyn.load the same code more than once?

Hi.  I'm still working on figuring out why some C code that interfaced
nicely with R-1.1.1 is causing segmentation faults in R-1.2.0.  Brian
Ripley advised me that R-1.2.0 can be more sensitive to array overruns
than was R-1.1.1, so I'm looking for overruns.  But in the course of
running R with a debugger I've come across something else.

Without thinking about it much, I put the dyn.load statement loading my
compiled code into the function immediately before the code is called.
This means that the dyn.load call is being executed over and over.  This
has never seemed to cause a problem, but under the debugger I get an error
after several times that some address cannot be accessed (the exact
address changes from time to time).  If I'm not in the debugger, this
doesn't happen, but perhaps it has something to do with my eventual memory
corruption.

So my question is:  can multiple loading of code cause a problem?  If so,
what kind? 

Also, I'll try loading the code in my .First function instead.  Can this
lead to any problems (like memory issues if I load lots of functions)?

I'm working on an alpha running Red Hat Linux.

Thanks,

Matt Wiener


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On Fri, 5 Jan 2001, Matthew Wiener wrote:
> 
> Hi.  I'm still working on figuring out why some C code that interfaced
> nicely with R-1.1.1 is causing segmentation faults in R-1.2.0.  Brian
> Ripley advised me that R-1.2.0 can be more sensitive to array overruns
> than was R-1.1.1, so I'm looking for overruns.  But in the course of
> running R with a debugger I've come across something else.
> 
> Without thinking about it much, I put the dyn.load statement loading my
> compiled code into the function immediately before the code is called.
> This means that the dyn.load call is being executed over and over.  This
> has never seemed to cause a problem, but under the debugger I get an error
> after several times that some address cannot be accessed (the exact
> address changes from time to time).  If I'm not in the debugger, this
> doesn't happen, but perhaps it has something to do with my eventual
memory
> corruption.
> 
> So my question is:  can multiple loading of code cause a problem?  If so,
> what kind? 
Well, there are finite resources in src/unix/dynload.c, like for 100
loads.
> Also, I'll try loading the code in my .First function instead.  Can
this
> lead to any problems (like memory issues if I load lots of functions)?
Not at all.  You only load the code, don't find all the entry points.
It is what we advise.
> 
> I'm working on an alpha running Red Hat Linux.
> 
> Thanks,
> 
> Matt Wiener
> 
> 
>
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> r-help mailing list -- Read http://www.ci.tuwien.ac.at/~hornik/R/R-FAQ.html
> Send "info", "help", or "[un]subscribe"
> (in the "body", not the subject !)  To: r-help-request at
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>
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> 
-- 
Brian D. Ripley,                  ripley at stats.ox.ac.uk
Professor of Applied Statistics,  http://www.stats.ox.ac.uk/~ripley/
University of Oxford,             Tel:  +44 1865 272861 (self)
1 South Parks Road,                     +44 1865 272860 (secr)
Oxford OX1 3TG, UK                Fax:  +44 1865 272595

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