Thread safety

The IO-Fortran-Library promotes thread-safety by explicitly enforcing recursion with the recursive keyword on all module procedures. However, performing I/O in parallel regions has the tendency to result in unexpected behavior. For instance, inspect the output of the following program with multiple coarray images:

program main
    use io_fortran_lib
    implicit none (type, external)

    call echo("Hello from image "//str(this_image()), file="hello.txt")
end program main

This program will result in conflicts as multiple images attempt to write to the same file concurrently. The proper way to compose this program is by nesting echo inside a critical block to enforce strict thread-safety in the region:

program main
    use io_fortran_lib
    implicit none (type, external)

    critical
        call echo("Hello from image "//str(this_image()), file="hello.txt")
    end critical
end program main

Another common scenario involves performing I/O on a single image, which is thread-safe:

program main
    use io_fortran_lib
    implicit none (type, external)

    if ( this_image() == 1 ) then
        call echo("Hello from image "//str(this_image()), file="hello.txt")
    end if
end program main