[Bug fortran/96986] [8/9/10/11 Regression] Explicit interface required: volatile argument for ENTRY subroutine

["sgk at troutmask dot apl.washington.edu" <gcc-bugzilla@gcc.gnu.org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=96986

--- Comment #7 from Steve Kargl <sgk at troutmask dot apl.washington.edu> ---
On Sat, Jan 02, 2021 at 07:53:17PM +0000, anlauf at gcc dot gnu.org wrote:
> https://gcc.gnu.org/bugzilla/show_bug.cgi?id=96986
> 
> --- Comment #6 from anlauf at gcc dot gnu.org ---
> (In reply to kargl from comment #5)
> >    If the ENTRY statement is in a subroutine subprogram, an additional
> >    subroutine is defined by that subprogram.  The name of the subroutine
> >    is entry-name. The dummy arguments of the subroutine are those
> >    specified in the ENTRY statement
> 
> Well, I stumbled over the "additional subroutine".
> 
> I assume that the "additional subroutine" wouldn't exist without the containing
> subprogram in the first place.  Maybe a consultation of c.l.f. could help.
> 

Not sure what you think clf will provide.  Seems clear to me that

subroutine volatile_test()
   integer, volatile :: va
   entry fun_a()
   return
   entry fun_b(va)
      call fun_c()
   return
end subroutine volatile_test

is equivalent

subroutine volatile_test()
   integer, volatile :: va
   return
      call fun_c()
   return
end subroutine volatile_test

subroutine fun_a()
   integer, volatile :: va
   return
      call fun_c()
   return
end subroutine fun_a()

subroutine fun_b(va)
   integer, volatile :: va
   call fun_c()
   return
end subroutine fun_b 

Here, only fun_b() requires an explicit interface if it is
used in another scoping unit.  AFAICT, a programmer is  
required to add 

interface
   subroutine fun_b(va)
      integer, volatile :: va
   end subroutine fun_b
end interface

to that scoping unit.