[Bug fortran/93599] New: [9/10 regression] Bug in fortran asynchronous I/O wait function

[seurer at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=93599

            Bug ID: 93599
           Summary: [9/10 regression] Bug in fortran asynchronous I/O wait
                    function
           Product: gcc
           Version: 10.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: fortran
          Assignee: unassigned at gcc dot gnu.org
          Reporter: seurer at gcc dot gnu.org
  Target Milestone: ---

The test case testsuite/libgomp.fortran/async_io_4.f90 fails erratically on
powerpc64 often with thousands, even tens of thousands, of successful runs
between failures.  It fails on both LE and BE and on power 7, 8, and 9. 
Looking at the gcc test results mailing list I see a few failures for this on
aarch64 and even one for x86 as well though I do not know if it is the same
issue.

>From testing today the failures have occurred since the test case was added in
gcc 9 in svn revision r263750 which is
g:2b4c90656132abb8b8ad155d345c7d4fbf1687c9, r9-2544.  This revision is

    Author: Nicolas Koenig <koenigni@gcc.gnu.org>
    Date:   Tue Aug 21 18:48:59 2018 +0000
    re PR fortran/25829 ([F03] Asynchronous IO support)


When it fails it always fails at the "stop 1" (see below).  It looks like the
call "wait (20)" is what is not working as when it hits the stop 1 the value of
the variable "i" is still 41.

The test case actually doesn't fail (I hesitate to say it works) if built with
a compiler from before this revision.  (note the test case was actually added
in this revision) 


Before the revision the call to wait becomes:

bl _gfortran_st_wait

0x00000000100009a0               
00000035.plt_call._gfortran_st_wait@@GFORTRAN_8

after the revision it becomes

bl _gfortran_st_wait_async

0x0000000010000b20               
00000035.plt_call._gfortran_st_wait_async@@GFORTRAN_9


I am not sure if that is something in the fortran library or what.


Shortened test case from testsuite/libgomp.fortran/async_io_4.f90:

! { dg-do run { target fd_truncate } }
!TODO: Move these testcases to gfortran testsuite
! once compilation with pthreads is supported there

! Test BACKSPACE for synchronous and asynchronous I/O
program main

  integer i, n, nr
  real x(10), y(10)

  ! PR libfortran/20068
  open (20, status='scratch', asynchronous="yes")
  write (20,*, asynchronous="yes" ) 1
  write (20,*, asynchronous="yes") 2
  write (20,*, asynchronous="yes") 3
  rewind (20)
  i = 41
  read (20,*, asynchronous="yes") i
  wait (20)
  if (i .ne. 1) stop 1

end program