How to expand the scope of a subroutine inside a subroutine?

3

Thank you @ivanpribec . Yeah the example I showed is not too good.
The real code contains a little bit MPI, and it is more like

subroutine A(...)
...
do i = 1, n
  if ( rank ==0 ) then
! rank 0 cpu do the job. 
! However at some point if rank 0 find error, 
! it wants to inform all the cores to return
  ... long god damn code ...
    if (detected some error) then
     quit= .true. 
     goto 100
    else
      quit = .false. 
    endif
  ...  long god damn code  ...
  endif
100 continue
  call broadcast(quit) 
  if (quit) then return
! all core will wait here for rank 0 to broadcast if quit or not. 
! if quit is true then all the cores return.
enddo
...
end subroutine A

  1. It looks like in this case, if rank 0 detects some error, and it wants all the cores to return, I can think of the not-so-adorable goto statement is convenient. All the cores will run at 100, and wait for the broadcast, when quit is true, all the cores return subroutine A.
    Is there some other way can achieve this?
    I mean, if rank 0 detects something wrong, if inform all the cores to stop or return or whatever.

  2. if I want to make

  ... long god damn code ...
    if (detected some error) then
     quit= .true. 
     goto 100
    else
      quit = .false. 
    endif
  ...  long god damn code  ...

into a sub subroutine inside subroutine A, call it longcode, like

subroutine A(...)
...
do i = 1, n
  if ( rank ==0 ) then
! rank 0 cpu do the job. 
! However at some point if rank 0 find error, 
! it wants to inform all the cores to return
    call longcode(...)
  endif
100 continue
  call broadcast(quit) 
  if (quit) then return
! all core will wait here for rank 0 to broadcast if quit or not. 
! if quit is true then all the cores return.
enddo
...
contains
subroutine longcode(...)
! seems need to use alternative return, 
! so that it return to 100 in the main subroutine. 
end subroutine longcode
end subroutine A

It seems the alternative return will be needed in sub subroutine longcode.
Is there some more modern way that can let sub subroutine longcode jump to some places in the main subroutine A?

Sorry it is a little bit chaotic, lol.

Is there cases where goto statement is really useful and needed?