Calling Fortran from R: "Funny sized logical array"

Question

Here is a funny problem I am encountering with R and Fortran.

Consider the following Fortran subroutine:

! foo.f90
subroutine fun(n, x)
  implicit none
  integer, intent(in) :: n
  logical, intent(in) :: x(n)
  integer :: i

  write(*,*) pack([(i, i=1, n)], x)

end subroutine fun

When compiled with R CMD SHLIB foo.f90 and called in R with

dyn.load("foo.so")
x <- c(TRUE ,FALSE)
f <- .Fortran("fun", 2L, as.logical(x))

I get the error message:

Fortran runtime error: Funny sized logical array

When the same subroutine is called from a Fortran program,

! test.f90
program test
  implicit none
  logical :: x(2)

  x = [.true., .false.]
  call fun(2, x)

contains

  include "foo.f90"

end program test

no error occurs:

$ gfortran foo.f90 test.f90 -o test
$ ./test 
           1

Potential culprit: The Fortran compiler I am using for this example. I used GNU Fortran 9.2.1. I noticed the same problem with gfortran 8.3.0, but no errors with earlier versions 7.4.0, 6.5.0 and 5.5.0. But why would the Fortran program test.f90 with the same subroutine work here? (even when the same flags used by R CMD SHLIB are used to compile foo.f90 and test.f90: -fno-optimize-sibling-calls -fpic -ggdb -O0 -Wall -Wextra -pedantic -fimplicit-none -fcheck=all -fbacktrace).

This looked funny at the beginning, but after some time playing around with this problem, this is getting frustrating...

Thanks in advance for your help.

More details:

> sessionInfo()
R version 3.6.1 (2019-07-05)
Platform: x86_64-pc-linux-gnu (64-bit)
Running under: Ubuntu 18.04.3 LTS

Matrix products: default
BLAS:   /usr/lib/x86_64-linux-gnu/blas/libblas.so.3.7.1
LAPACK: /usr/lib/x86_64-linux-gnu/lapack/liblapack.so.3.7.1

locale:
 [1] LC_CTYPE=en_US.UTF-8       LC_NUMERIC=C              
 [3] LC_TIME=en_US.UTF-8        LC_COLLATE=en_US.UTF-8    
 [5] LC_MONETARY=en_US.UTF-8    LC_MESSAGES=en_US.UTF-8   
 [7] LC_PAPER=en_US.UTF-8       LC_NAME=C                 
 [9] LC_ADDRESS=C               LC_TELEPHONE=C            
[11] LC_MEASUREMENT=en_US.UTF-8 LC_IDENTIFICATION=C       

attached base packages:
[1] stats     graphics  grDevices utils     datasets  methods   base     

loaded via a namespace (and not attached):
[1] compiler_3.6.1

Calling Fortran from R: "Funny sized logical array"

0 Answers