Comp Sci Can‘t call a subroutine name in a subroutine in Fortran90

[pilipili2021]

Homework Statement

Coding by ifort
Try to call a uncertain name subroutine

Relevant Equations

NONE

Here is the code for example:

PROGRAM  main
  CALL B()
  CALL CaoB(B)
  
  contains
   
  subroutine B()
  IMPLICIT NONE
  write (*,*) 'fk'
  end subroutine B

 subroutine CaoB(fcn)
 implicit none

 INTERFACE
   SUBROUTINE fcn()
     IMPLICIT NONE
   END SUBROUTINE fcn
 END INTERFACE

 write (*,*) '1'
 call B() 
 write (*,*) '2'
 call fcn()
 write (*,*) '3'

 end subroutine CaoB 

END

Then I compile it.

ifort main.F90

It seems no error. Then run it.

./a.outIt show that

fk
1
fk
2
forrtl: severe (174): SIGSEGV, segmentation fault occurred
Image PC Routine Line Source
a.out 000000000040492A Unknown Unknown Unknown
libpthread-2.31.s 00007F15A65153C0 Unknown Unknown Unknown
Unknown 00007FFFC18B82C0 Unknown Unknown Unknown

Surely there is something wrong when I call the subroutine fcn, which it should be named as B.

So, what should I do? what's wrong? Please let me know if any of you have any ideas or any comments.

thank you

 

[BvU]

which it should be named as B

How does the main program know that ?
[edit] Or rather: the calling program, in this case CaoB

$\$

 

[pilipili2021]

How does the main program know that ?

$\$

Thank you for your reply.

Do you mean add some code like 'external B' or 'external fcn'? That not works.

In the subroutine 'CaoB' it have a subroutine name 'fcn' determined by the interface. When I call 'CaoB(B)', 'B' as a subroutine name should be instead of 'fcn' in the subroutine 'CaoB'. It should be, but something goes wrong.

 

[DrClaude]

Your program appears to be fine. I have checked both with GNU Fortran (GCC) 10.2.0 and ifort version 2021.2.0 20210228.

 

[pilipili2021]

Thank you for your reply！
It's a great help.
May be my environment have some problems.
my ifort version is 2021.4.0

So confused.

 

[DrClaude]

Thank you for your reply！
It's a great help.
May be my environment have some problems.
my ifort version is 2021.4.0

So confused.

Problems are usually fixed with newer versions .

By the way, my ifort is on Linux.

 

[pilipili2021]

Problems are usually fixed with newer versions .

By the way, my ifort is on Linux.

My ifort is on ubuntu 20.04 , also on Linux.
Everything worked well before my hard disk suddenly broken.
May problems created with newer versions

 

[pilipili2021]

finally I find the problem.

If I code like

Call CaoB()
contains
subroutine B()

the error comes.

If I move subroutine B out of 'contains' like

subroutine B()

subroutine something
call CaoB()
end subroutine something

Then the problem is solved.