[Rd] R/C++/memory leaks

Hin-Tak Leung hin-tak.leung at cimr.cam.ac.uk
Mon Feb 26 11:51:45 CET 2007

Read the help page of gc(). You need to run it with reset=TRUE for
the usage to drop back to original. i.e. gc(reset=TRUE). gc() on its
own doesn't quite do what you think it would do.

Ernest Turro wrote:
> Dear all,
> I have wrapped a C++ function in an R package. I allocate/deallocate  
> memory using C++ 'new' and 'delete'. In order to allow user  
> interrupts without memory leaks I've moved all the delete statements  
> required after an interrupt to a separate C++ function freeMemory(),  
> which is called using on.exit() just before the .C() call.
> I am concerned about the following. In square brackets you see R's  
> total virtual memory use (VIRT in `top`):
> 1) Load library and data [178MB] (if I run gc(), then [122MB])
> 2) Just before .C [223MB]
> 3) Just before freeing memory [325MB]
> 4) Just after freeing memory [288MB]
> 5) After running gc() [230MB]
> So although the freeMemory function works (frees 37MB), R ends up  
> using 100MB more after the function call than before it. ls() only  
> returns the data object so no new objects have been added to the  
> workspace.
> Do any of you have any idea what could be eating this memory?
> Many thanks,
> Ernest
> PS: it is not practical to use R_alloc et al because C++ allocation/ 
> deallocation involves constructors/destructors and because the C++  
> code is also compiled into a standalone binary (I would rather avoid  
> maintaining two separate versions).
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