gfortran -std=f2008 compile flag errors if call fseek present - fortran

Question

I'm trying to enforce a Fortran 2008 consistency check with gfortran. When I compile with -std=f2008, I get the following error:
Undefined symbols for architecture x86_64:
"_fseek_", referenced from:
_MAIN__ in ccJtOcKa.o
ld: symbol(s) not found for architecture x86_64
collect2: error: ld returned 1 exit status
The following simple test program shows the issue. It compiles and runs fine without the -std=f2008, but doesn't compile when this flag is set.
program main
implicit none
integer :: i
open(unit=10, file='test.bin', access='stream')
write(10) 100
!fseek works, but will not compile with -std=f2008
call fseek(10, -4, 1)
read(10) i
print *, i
end program
This works:
gfortran main.f90
This gives the error:
gfortran -std=f2008 main.f90
I'm using MacPorts version of gfortran 8.2
GNU Fortran (MacPorts gcc8 8.2.0_3) 8.2.0
Copyright (C) 2018 Free Software Foundation, Inc.
This is free software; see the source for copying conditions. There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
Is fseek not a part of the fortran 2008 standard? If so, is there an alternative way to do this?

Answer 1

FSEEK an an extension intrinsic subroutine which is unnecessary for stream access. You can just read from any position you want
read(10, pos=42) i
You can also get the current position with the inquire statement.
inquire(unit=10, pos=current_pos)

Answer 2

As others have indicated, FSEEK is not in a Fortran standard. The Fortran standard does, however, permit a processor to supply additional intrinsics subprograms. To avoid the problem you are having, you can use the -fall-intrinsics option. Thus, gfortran -std=f2008 -fall-intrinsics will try to adhere to the Fortran 2008 standard with the exceptional that all intrinsic subprograms supplied by gfortran are available.