Problem with openacc routine and character variable

Hello, I am trying to use openacc in a fortran software. This subroutine can reproduce the problem that I have at the moment:

!$acc routine (NN) seq
      SUBROUTINE NN(C)
      CHARACTER(LEN=20) C    
      CHARACTER(LEN=20) PARM_TMP
      
      PARM_TMP = "HELLO"

      C = PARM_TMP
      RETURN
      END

But when I compile it, it fails:

pgf90 -Mnomain  -acc -ta=nvidia -Minfo=accel -I./  -c m4.f 
PGF90-S-0000-Internal compiler error. Call in OpenACC region to procedure with no acc routine information - pgf90_str_copy (m4.f: 10)
nn:
      2, Generating acc routine seq
      8, Accelerator restriction: call to 'pgf90_str_copy' with no acc routine information
  0 inform,   0 warnings,   1 severes, 0 fatal for nn

Any clue?

Hi esepulveda26247,

Unfortunately we don’t support the Fortran string library on the device. We’ll eventually move the entire Fortran run time over to the device, but for now you wont be able to perform string manipulation in OpenACC device code with PGI.

Sorry,
Mat