[Bug fortran/51286] New: function with print statement hangs when called as argument of a print statement

[Bug fortran/51286] New: function with print statement hangs when called as argument of a print statement

[stefano.borini at ferrara dot linux.it]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=51286

             Bug #: 51286
           Summary: function with print statement hangs when called as
                    argument of a print statement
    Classification: Unclassified
           Product: gcc
           Version: 4.6.2
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: fortran
        AssignedTo: unassigned@gcc.gnu.org
        ReportedBy: stefano.borini@ferrara.linux.it


This code hangs due to the "whatever" printing statement inside the function,
when called as an argument to print.

Wild guess is that it tries to get some lock during the Squared print, which is
already taken by the caller, but it's pure speculation. 

Tested on ifort, works as expected (no hang, two prints).

module Moo
contains
   subroutine main()

      print *, Squared(5)

   end subroutine

   function Squared(v)
      integer, intent(in) :: v
      integer :: Squared
      Squared = v*v
      print *, "whatever"
   end function
end module
program foo
   use Moo
   call main()
end program

[Bug fortran/51286] function with print statement hangs when called as argument of a print statement

[kargl at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=51286

kargl at gcc dot gnu.org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |kargl at gcc dot gnu.org

--- Comment #1 from kargl at gcc dot gnu.org 2011-11-23 18:06:09 UTC ---
Your code is invalid, because it is doing trying to do 
recursive IO.  From the Fortran 2003 standard:


An input/output statement that is executed while another
input/output statement is being executed is called a
recursive input/output statement.

A recursive input/output statement shall not identify an
external unit except that a child data transfer statement
may identify its parent data transfer statement external unit.

A data transfer statement that includes a derived-type
list item and that causes a user-defined derived-type
input/output procedure to be invoked is called a parent
data transfer statement.  A data transfer statement that
is executed while a parent data transfer statement is being
processed and that specifies the unit passed into a
user-defined derived-type input/output procedure is called
a child data transfer statement.

You are invoking undefined behavior, and are clearly 
getting an acceptable result.

[Bug fortran/51286] function with print statement hangs when called as argument of a print statement

[dominiq at lps dot ens.fr]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=51286

--- Comment #2 from Dominique d'Humieres <dominiq at lps dot ens.fr> 2011-11-23 18:26:41 UTC ---
Aren't you using some Mac OSX? If so, it is a duplicate of pr30617.

[Bug fortran/51286] function with print statement hangs when called as argument of a print statement

[dominiq at lps dot ens.fr]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=51286

Dominique d'Humieres <dominiq at lps dot ens.fr> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |RESOLVED
         Resolution|                            |DUPLICATE

--- Comment #3 from Dominique d'Humieres <dominiq at lps dot ens.fr> 2013-02-27 18:18:37 UTC ---
> Aren't you using some Mac OSX? If so, it is a duplicate of pr30617.

No answer, so closing as duplicate.

*** This bug has been marked as a duplicate of bug 30617 ***