[Numpy-discussion] f2py: Can anyone tell me why this simple call-back example fails?

Dave Lang dave.seattledl@gmail....
Wed Nov 12 18:06:44 CST 2008


My system......

Ubuntu v8.0.4;   Gnu gcc v4.0.3;    g95  v0.92

Python  v2.5.2;    Numpy v1.2.1;    f2py  v2.5972

Hope someone can see what's wrong here?

thanks

Dave Lang


..............Here is the F90 code...........
! PROGRAM TO DEMONSTRATE PYTHON-->F90  AND  F90-->PYTHON INTERFACE
        SUBROUTINE CBSET(N, call_back)
!f2py   intent(in) N
!f2py   intent(callback) call_back
        EXTERNAL call_back
        INTEGER N, m

! IDENTIFY THAT FORTRAN IS EXECUTING & WHO CALLED CBSET
        PRINT *,'Enter CBSET.F, N=',N

        IF(N .EQ. 1) THEN
           PRINT *,'  in CBSET: This Call originated to test call-back'
           PRINT *,'  in CBSET: Make callback to PYTHON...EXPECT reply'
           m=1
           CALL call_back(m)
           PRINT *,'  in CBSET: Returned from call-back to PYTHON'
        END IF

        IF(N .EQ. 2) THEN
           PRINT *,'  in CBSET: Call came from Python to test Py->For'
        END IF

        RETURN
        END


..............Here is the f2py created Signature code...........
!    -*- f90 -*-
! Note: the context of this file is case sensitive.

python module cbset__user__routines
    interface cbset_user_interface
        subroutine call_back(m) ! in :foo:CBSET.F90:cbset:unknown_interface
            intent(callback) call_back
            integer :: m
        end subroutine call_back
    end interface cbset_user_interface
end python module cbset__user__routines
python module foo ! in
    interface  ! in :foo
        subroutine cbset(n) ! in :foo:CBSET.F90
            use cbset__user__routines
            integer intent(in) :: n
            intent(callback) call_back
            external call_back
        end subroutine cbset
    end interface
end python module foo

! This file was auto-generated with f2py (version:2_5972).
! See http://cens.ioc.ee/projects/f2py2e/



..............Here is the Python Main Program code...........
# Main Python program to test nominal "wrap" and "call back"
import foo

def main():
    print 'HELLO, pymain is about to call CBSET to test f2py operation'
    print 'BUT, 1st test call_back subr from within python itself'
    call_back(979)

#test "Python --> FORTRAN" (nominal wrap) from Python
    print 'NOW, call CBSET to test Python --> FORTRAN wrap'
    n = 2
    foo.cbset(n, call_back)

#test "FORTRAN --> Python" (call-back) scheme as seen from Python
    print 'NOW, call CBSET to test FORTRAN --> Python call-back'
    n = 1
    foo.cbset(n, call_back)

# define call-back routine
def call_back(m):
        m +=20
        print '..Confirming call_back, Python is entered from Fortran'
        print '..in call_back: m = ', m
        return
# end of call-back defn

if __name__ =='__main__':
    main()


..............Here is the execution result...........
david@david-desktop:~/Pyth/ACB$ python pymain.py
HELLO, pymain is about to call CBSET to test f2py operation
BUT, 1st test call_back subr from within python itself
..Confirming call_back, Python is entered from Fortran
..in call_back: m =  999
NOW, call CBSET to test Python --> FORTRAN wrap
 Enter CBSET.F, N=           2
   in CBSET: Call came from Python to test Py->For
NOW, call CBSET to test FORTRAN --> Python call-back
 Enter CBSET.F, N=           1
   in CBSET: this Call originated to test call-back
   in CBSET: Make callback to PYTHON...EXPECT reply
Segmentation fault
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