[Rd] The finalizer of the externalPtr does not work when closing R?

[Tomas Kalibera]

+ 5.13 of Writing R Extensions

Tomas
On 4/3/20 3:04 PM, Gábor Csárdi wrote:
> See R_RegisterCFinalizerEx() and set onexit to nonzero. Here:
> https://github.com/wch/r-source/blob/9353ddfa8d30069ad8975e0364307d710f2488d5/src/include/Rinternals.h#L1279-L1280
>
> Gabor
>
> On Fri, Apr 3, 2020 at 1:56 PM Wang Jiefei <szwjf08 using gmail.com> wrote:
>> Hi all,
>>
>> I found that the finalizer of the externalPtr is not called when R is
>> quitting. However, manually calling GC() works fine. This behavior is
>> observed on devel R 2020-04-02 r78142 on Win and R 3.6.3 on Ubuntu.  I make
>> a reproducible package here: https://github.com/Jiefei-Wang/example
>>
>> Here is the detail of how to reproduce the problem, I create a temporary
>> file in the package root path and make an external pointer. The finalizer
>> of the external pointer will delete the  temporary file when it is called.
>> In the first round, I manually remove the external pointer from the global
>> environment and call GC() to verify if the finalizer is programmed
>> properly. The temporary file is deleted successfully. Then I create the
>> file and the pointer again and close the R session without saving the
>> global environment. Since the external pointer is removed when closing R,
>> so the finalizer should be called in this procedure. However, the temp file
>> still exists after closing the R session.
>>
>> Here is the test code(which can be found in inst/example/example.R)
>>
>> ## Create a temporary file
>> tmpFile <- paste0(system.file(package = "testPackage"), "/tmp")
>> tmpFile
>> file.create(tmpFile)
>> file.exists(tmpFile)
>> ## Create an external pointer whose finalizer will delete
>> ## the file when the variable is not in used
>> x <- testPackage:::makeExtPtr(file.remove,tmpFile)
>> ## GC is working fine
>> rm(list="x")
>> gc()
>> file.exists(tmpFile)
>>
>> ## Create the temporary file again
>> file.create(tmpFile)
>> file.exists(tmpFile)
>> x <- testPackage:::makeExtPtr(file.remove,tmpFile)
>> ## Quit R session without explicitly cleaning the working space
>> quit(save = "no")
>>
>>
>> ##=====Open a new R session=======
>> ## The temporary file still exist
>> tmpFile <- paste0(system.file(package = "testPackage"), "/tmp")
>> file.exists(tmpFile)
>>
>> Not sure if this behavior is designed on purpose, but it sounds wired to me
>> and can cause memory leaking if not properly handled.
>>
>> Best,
>> Jiefei
>>
>>          [[alternative HTML version deleted]]
>>
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