Error: Unable to load gfortran compiled DLL in R ("symbol name not in load table")

Question

Well, I recently fell in love with Fortran (f90) and have been trying to understand the "kung-fu" of R and Fortran. I found several relevant and helpful questions here (e.g. this and this).

What I am trying to do:

I am (probably, trying to do something crazy) trying to call the following .f90 subroutines in R (x64) using .Fortran() function. Here is the test.f90 code:

! Computes the square of a number

Subroutine sr1(a,b)
!DEC$ ATTRIBUTES DLLEXPORT::sr1
!DEC$ ATTRIBUTES C, REFERENCE, ALIAS:'sr1' :: sr1

implicit none
integer a,b
b = a*a
End Subroutine sr1

! Computes the cube of a number
Subroutine sr2(x,y)   
!DEC$ ATTRIBUTES DLLEXPORT::sr2
!DEC$ ATTRIBUTES C, REFERENCE, ALIAS:'sr2' :: sr2

implicit none
integer x,y
y = x*x*x
End Subroutine sr2

I am compiling the above test.f90 code via gfortran on my Windows 10 machine by:

gfortran -shared -o test.dll test.f90

The compilation works and I get the test.dll. Now, in R. I try to load it:

 dyn.load("path_to_file/test.dll")

It works. But, it fails here:

> is.loaded("test")
[1] False

I already found a relevant question here. But, I could not get the clue to fix my problem. Can someone suggest some workaround to fix the issue?

Answer 1

I am not a big user of R, but my tests show that while

is.loaded("test_R")

indeed returns FALSE, both

is.loaded("sr1")

and

is.loaded("sr2")

return TRUE. But I did my tests on Linux and GCC which may interpret the extrnally visible subroutine names differently.