• I am reporting a bug others will be able to reproduce and not asking a question or requesting a new feature.

System information including:

• OpenCoarrays Version: 2.10.1
• Fortran Compiler: gfortran gcc version 11.3.0 (Ubuntu 11.3.0-1ubuntu1~22.04)
• C compiler used for building lib: gcc version 11.3.0
• Installation method: Cmake from source using git clone (followed instructions from Modern Fortran by Milan Curic)

cd OpenCoarrays
mkdir build
cd build
FC=gfortran CC=gcc cmake ..
make
make install

• All flags & options passed to the installer: FC=gfortran, CC=gcc
• Output of uname -a: Linux DESKTOP-OB8O7DS 5.10.16.3-microsoft-standard-WSL2 #1 SMP Fri Apr 2 22:23:49 UTC 2021 x86_64 x86_64 x86_64 GNU/Linux
• MPI library being used: Debian OpenMPI v.4.1.2
• Machine architecture and number of physical cores: x86_64, 4 physical cores, 2 threads/core
• Version of CMake: 3.22.1

To help us debug your issue please explain:

What you were trying to do (and why)

I'm trying to run cafrun in serial. The bug occurred for the tally test from https://github.com/sourceryinstitute/OpenCoarrays/blob/main/GETTING_STARTED.md. However, the same bug also occurred running the serial program ./weather_stats (my original goal), compiled from https://github.com/modern-fortran/weather-buoys.

What happened (include command output, screenshots, logs, etc.)

cafrun -np 4 tally yielded Test passed as expected.
However, simply running ./tally or cafrun -np 1 tally yields the following:

[DESKTOP-OB8O7DS:10249] *** An error occurred in MPI_Win_create
[DESKTOP-OB8O7DS:10249] *** reported by process [304545793,0]
[DESKTOP-OB8O7DS:10249] *** on communicator MPI COMMUNICATOR 3 DUP FROM 0
[DESKTOP-OB8O7DS:10249] *** MPI_ERR_WIN: invalid window
[DESKTOP-OB8O7DS:10249] *** MPI_ERRORS_ARE_FATAL (processes in this communicator will now abort,
[DESKTOP-OB8O7DS:10249] *** and potentially your MPI job)

Cloning the Modern Fortran weather-buoys repo and compiling weather_stats, the same thing occured: the program ran with 2 processors but not 1. When run with 1 processor, I get the above error.

What you expected to happen

I expected Test passed as before.

Step-by-step reproduction instructions to reproduce the error/bug

$ cat tally.f90
 program main
 use iso_c_binding, only : c_int
 use iso_fortran_env, only : error_unit
 implicit none
 integer(c_int) :: tally
 tally = this_image() ! this image's contribution
 call co_sum(tally)
 verify: block
 integer(c_int) :: image
 if (tally/=sum([(image,image=1,num_images())])) then
 write(error_unit,'(a,i5)') "Incorrect tally on image ",this_image()
 error stop
 end if
 end block verify
 ! Wait for all images to pass the test
 sync all
 if (this_image()==1) print *,"Test passed"
 end program
$ caf tally.f90 -o tally
$ cafrun -np 1 ./tally

OR for the weather-buoy example

git clone https://github.com/modern-fortran/weather-buoys.git
cd weather-buoys
make weather_stats
./weather_stats