[Patch, fortran] PR87127 - External function not recognised from within an associate block

[Paul Richard Thomas <paul dot richard dot thomas at gmail dot com>]

This patch is pretty self-explanatory. I have checked that a sensible
errors are given if 'exfunc' in the testcase is referenced if it is a
variable.

Bootstrapped and regtested on FC29/x86_64 - OK for trunk?

Paul

2019-03-30  Paul Thomas  <pault@gcc.gnu.org>

    PR fortran/87127
    * resolve.c (check_host_association): If an external function
    is typed but not declared explicitly to be external, change the
    old symbol from a variable to an external function.

2019-03-30  Paul Thomas  <pault@gcc.gnu.org>

    PR fortran/87127
    * gfortran.dg/external_procedures_4.f90: New test.

Index: gcc/fortran/resolve.c
===================================================================
*** gcc/fortran/resolve.c	(revision 269160)
--- gcc/fortran/resolve.c	(working copy)
*************** resolve_procedure:
*** 5615,5625 ****


  /* Checks to see that the correct symbol has been host associated.
!    The only situation where this arises is that in which a twice
!    contained function is parsed after the host association is made.
!    Therefore, on detecting this, change the symbol in the expression
!    and convert the array reference into an actual arglist if the old
!    symbol is a variable.  */
  static bool
  check_host_association (gfc_expr *e)
  {
--- 5615,5628 ----


  /* Checks to see that the correct symbol has been host associated.
!    The only situations where this arises are:
! 	(i)  That in which a twice contained function is parsed after
! 	     the host association is made. On detecting this, change
! 	     the symbol in the expression and convert the array reference
! 	     into an actual arglist if the old symbol is a variable; or
! 	(ii) That in which an external function is typed but not declared
! 	     explicitly to be external. Here, the old symbol is changed
! 	     from a variable to an external function.  */
  static bool
  check_host_association (gfc_expr *e)
  {
*************** check_host_association (gfc_expr *e)
*** 5709,5714 ****
--- 5712,5737 ----
  	  gfc_resolve_expr (e);
  	  sym->refs++;
  	}
+       /* This case corresponds to a call, from a block or a contained
+ 	 procedure, to an external function, which has not been declared
+ 	 as being external in the main program but has been typed.  */
+       else if (sym && old_sym != sym
+ 	       && !e->ref
+ 	       && sym->ts.type == BT_UNKNOWN
+ 	       && old_sym->ts.type != BT_UNKNOWN
+ 	       && sym->attr.flavor == FL_PROCEDURE
+ 	       && old_sym->attr.flavor == FL_VARIABLE
+ 	       && sym->ns->parent == old_sym->ns
+ 	       && sym->ns->proc_name
+ 	       && (sym->ns->proc_name->attr.flavor == FL_LABEL
+ 		   || sym->ns->proc_name->attr.flavor == FL_PROCEDURE))
+ 	{
+ 	  old_sym->attr.flavor = FL_PROCEDURE;
+ 	  old_sym->attr.external = 1;
+ 	  old_sym->attr.function = 1;
+ 	  old_sym->result = old_sym;
+ 	  gfc_resolve_expr (e);
+ 	}
      }
    /* This might have changed!  */
    return e->expr_type == EXPR_FUNCTION;
Index: gcc/testsuite/gfortran.dg/external_procedures_4.f90
===================================================================
*** gcc/testsuite/gfortran.dg/external_procedures_4.f90	(nonexistent)
--- gcc/testsuite/gfortran.dg/external_procedures_4.f90	(working copy)
***************
*** 0 ****
--- 1,28 ----
+ ! { dg-do run }
+ !
+ ! Test the fix for PR87127 in which the references to exfunc cause
+ ! the error "‘exfunc’ at (1) is not a function".
+ !
+ ! Contributed by Gerhard Steinmetz  <gscfq@t-online.de>
+ !
+ function exfunc(i)
+   implicit none
+   integer :: exfunc,i
+   exfunc = 2*i
+ end function
+
+ ! contents of test.f90
+ program test
+   implicit none
+   integer :: exfunc,i
+   integer,parameter :: array(2)=[6,7]
+   associate(i=>array(2))            ! Original bug
+     if (exfunc(i) .ne. 2*i) stop 1
+   end associate
+   i = 99
+   call foo
+ contains
+   subroutine foo()                  ! Comment #3
+     if (exfunc(i) .ne. 2*i) stop 2
+   end subroutine foo
+ end program