[Rd] Request: Increasing MAX_NUM_DLLS in Rdynload.c

Henrik Bengtsson henrik.bengtsson at gmail.com
Tue Dec 20 07:04:28 CET 2016

On reason for hitting the MAX_NUM_DLLS (= 100) limit is because some
packages don't unload their DLLs when they being unloaded themselves.
In other words, there may be left-over DLLs just sitting there doing
nothing but occupying space.  You can remove these, using:


Maybe that will help you get through your tests (as long as you're
unloading packages).  gcDLLs() will look at base::getLoadedDLLs() and
its content and compare to loadedNamespaces() and unregister any
"stray" DLLs that remain after corresponding packages have been

I think it would be useful if R CMD check would also check that DLLs
are unregistered when a package is unloaded
(https://github.com/HenrikBengtsson/Wishlist-for-R/issues/29), but of
course, someone needs to write the code / a patch for this to happen.


On Mon, Dec 19, 2016 at 6:01 PM, Steve Bronder
<sbronder at stevebronder.com> wrote:
> This is a request to increase MAX_NUM_DLLS in Rdynload.c in from 100 to 500.
> On line 131 of Rdynload.c, changing
> #define MAX_NUM_DLLS 100
>  to
> #define MAX_NUM_DLLS 500
> In development of the mlr package, there have been several episodes in the
> past where we have had to break up unit tests because of the "maximum
> number of DLLs reached" error. This error has been an inconvenience that is
> going to keep happening as the package continues to grow. Is there more
> than meets the eye with this error or would everything be okay if the above
> line changes? Would that have a larger effect in other parts of R?
> As R grows, we are likely to see more 'meta-packages' such as the
> Hadley-verse, caret, mlr, etc. need an increasing amount of DLLs loaded at
> any point in time to conduct effective unit tests. If  MAX_NUM_DLLS is set
> to 100 for a very particular reason than I apologize, but if it is possible
> to increase MAX_NUM_DLLS it would at least make the testing at mlr much
> easier.
> I understand you are all very busy and thank you for your time.
> Regards,
> Steve Bronder
> Website: stevebronder.com
> Phone: 412-719-1282
> Email: sbronder at stevebronder.com
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