[Rd] [External] Something is wrong with the unserialize function

[iuke-tier@ey m@iii@g oii uiow@@edu]

Thanks for the report. Will look into it when I get a chance unless
someone else gets there first.

A simpler reprex:

## create and serialize a memmory-mapped file object
filePath <- "x.dat"
con <- file(filePath, "wrb")
writeBin(rep(0.0,10),con)
close(con)

library(simplemmap)
x <- mmap(filePath, "double")
saveRDS(x, file = "x.Rds")

## in a separate R process:
gctorture()
readRDS("x.Rds")

Looks like a missing PROTECT somewhere.

Best,

luke

On Thu, 29 Oct 2020, Jiefei Wang wrote:

> Hi all,
>
> I am not able to export an ALTREP object when `gctorture` is on in the
> worker. The package simplemmap can be used to reproduce the problem. See
> the example below
> ```
> ## Create a temporary file
> filePath <- tempfile()
> con <- file(filePath, "wrb")
> writeBin(rep(0.0,10),con)
> close(con)
>
> library(simplemmap)
> library(parallel)
> cl <- makeCluster(1)
> x <- mmap(filePath, "double")
> ## Turn gctorture on
> clusterEvalQ(cl, gctorture())
> clusterExport(cl, "x")
> ## x is an 0-length vector on the worker
> clusterEvalQ(cl, x)
> stopCluster(cl)
> ```
>
> you can find more info on the problem if you manually build a connection
> between two R processes and export the ALTREP object. See output below
> ```
>> con <- socketConnection(port = 1234,server = FALSE)
>> gctorture()
>> x <- unserialize(con)
> Warning message:
> In unserialize(con) :
>  cannot unserialize ALTVEC object of class 'mmap_real' from package
> 'simplemmap'; returning length zero vector
> ```
> It seems like  simplemmap did not get loaded correctly on the worker. If
> you run `library( simplemmap)` before unserializing the ALTREP, there will
> be no problem. But I suppose we should be able to unserialize objects
> without preloading the library?
>
> This issue can be reproduced on Ubuntu with R version 4.0.2 (2020-06-22)
> and Windows with R Under development (unstable) (2020-09-03 r79126).
>
> Here is the link to simplemmap:
> https://github.com/ALTREP-examples/Rpkg-simplemmap
>
> Best,
> Jiefei
>
> 	[[alternative HTML version deleted]]
>
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-- 
Luke Tierney
Ralph E. Wareham Professor of Mathematical Sciences
University of Iowa                  Phone:             319-335-3386
Department of Statistics and        Fax:               319-335-3017
    Actuarial Science
241 Schaeffer Hall                  email:   luke-tierney using uiowa.edu
Iowa City, IA 52242                 WWW:  http://www.stat.uiowa.edu