[J3] Is BIND (C [ , NAME = scalar-default-char-constant-expr ]) where scalar-default-char-constant-expr has zero length legal?

[Daniel C Chen]

Thanks Jon.

This makes sense and it is also the expected behavior of the user who
reported this issue. XLF, however, ignores the BIND attribute at the
moment. I couldn't find the wording in the standard that specifies the
behavior you have though.

Daniel

XL Fortran Development, Fortran Standard Representative
IBM Toronto Software Lab
Phone: 905-413-3056
Tie: 969-3056
Email: cdchen at ca.ibm.com
http://www.ibm.com/software/awdtools/fortran/xlfortran



From:	"Steidel, Jon L via J3" <j3 at mailman.j3-fortran.org>
To:	General J3 interest list <j3 at mailman.j3-fortran.org>
Cc:	"Steidel, Jon L" <jon.l.steidel at intel.com>
Date:	01/08/2019 11:31 AM
Subject:	Re: [J3] Is BIND (C [ , NAME =
            scalar-default-char-constant-expr ]) where
            scalar-default-char-constant-expr has zero length legal?
Sent by:	"J3" <j3-bounces at mailman.j3-fortran.org>



Hi Daniel,

Ifort (and NAG 6.1) appear to treat this as if NAME= was not specified.
When I simplified the test case to

program main
use iso_c_binding
interface
  subroutine foo (a) bind(c,name = "")
    real a
  end
end interface

call foo (1.0)
end

Both compilers compile without error or warning, and fail in the link/load
step with an undefined reference to “foo” or “foo_”.  So it looks like the
Fortran name is used when NAME= is a zero length string.

-jon
      From: J3 [mailto:j3-bounces at mailman.j3-fortran.org] On Behalf Of
      Daniel C Chen via J3
      Sent: Tuesday, January 8, 2019 11:06 AM
      To: General J3 interest list <j3 at mailman.j3-fortran.org>
      Cc: Daniel C Chen <cdchen at ca.ibm.com>
      Subject: [J3] Is BIND (C [ , NAME =
      scalar-default-char-constant-expr ]) where
      scalar-default-char-constant-expr has zero length legal?



      Consider the following code example:

      module example

      abstract interface
      subroutine sighandler_t(signum) bind(c)
      integer, value :: signum
      end subroutine
      end interface

      contains

      subroutine foo
      call bar(sighandler)
      end subroutine

      subroutine bar(proc)
      procedure(sighandler_t) :: proc
      end subroutine

      subroutine sighandler(signum) bind(c,name='') ! NAME has zero length
      integer, value :: signum
      print *, signum
      end subroutine sighandler

      end module

      At 8.5.5, the standard says

      R808 language-binding-spec is BIND (C [ , NAME = scalar-
      default-char-constant-expr ])
      ...
      "If the value of the scalar-default-char-constant-expr after
      discarding leading and trailing blanks has nonzero
      length, it shall be valid as an identifier on the companion processor
      ."

      But the standard doesn't specify what if the scalar-
      default-char-constant-exprhas zero length.

      Question: Should it be treated
      1. as if the NAME specified is not specified or
      2. the compiler should ignore the BIND attribute all together?

      Thanks,

      Daniel

      XL Fortran Development, Fortran Standard Representative
      IBM Toronto Software Lab
      Phone: 905-413-3056
      Tie: 969-3056
      Email: cdchen at ca.ibm.com
      http://www.ibm.com/software/awdtools/fortran/xlfortran





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