[Bug middle-end/46325] New: [4.6 Regression] gfortran.dg/char_initialiser_actual.f90 FAILs with -fstack-protector

[Bug middle-end/46325] New: [4.6 Regression] gfortran.dg/char_initialiser_actual.f90 FAILs with -fstack-protector

[zsojka at seznam dot cz]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=46325

           Summary: [4.6 Regression]
                    gfortran.dg/char_initialiser_actual.f90 FAILs with
                    -fstack-protector
           Product: gcc
           Version: 4.6.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: middle-end
        AssignedTo: unassigned@gcc.gnu.org
        ReportedBy: zsojka@seznam.cz


Output:
$ gfortran char_initialiser_actual.f90 -fstack-protector
$ ./a.out 
Aborted

Tested revisions:
r166306 - fail
r165699 - fail
r163636 - OK
4.5 r165781 - OK

[Bug middle-end/46325] [4.6 Regression] gfortran.dg/char_initialiser_actual.f90 FAILs with -fstack-protector

[hjl.tools at gmail dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=46325

H.J. Lu <hjl.tools at gmail dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |NEW
   Last reconfirmed|                            |2010.11.06 03:30:06
                 CC|                            |rth at gcc dot gnu.org
   Target Milestone|---                         |4.6.0
     Ever Confirmed|0                           |1

--- Comment #1 from H.J. Lu <hjl.tools at gmail dot com> 2010-11-06 03:30:06 UTC ---
It is caused by revision 165240:

http://gcc.gnu.org/ml/gcc-cvs/2010-10/msg00423.html

[Bug fortran/46325] [4.6 Regression] gfortran.dg/char_initialiser_actual.f90 FAILs with -fstack-protector

[jakub at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=46325

Jakub Jelinek <jakub at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Priority|P3                          |P4
                 CC|                            |jakub at gcc dot gnu.org
          Component|middle-end                  |fortran

--- Comment #2 from Jakub Jelinek <jakub at gcc dot gnu.org> 2010-11-10 16:07:32 UTC ---
The problem is that we choose to put A.19 and parm.22 into the same partition:

;; Function char_initialiser (MAIN__)

Partition 0: size 15 align 16
        x, offset 0
Partition 5: size 48 align 16
        parm.22, offset 0
        A.19, offset 0
Partition 3: size 48 align 16
        atmp.18, offset 0
Partition 4: size 48 align 16
        ptrtemp.16, offset 0
Partition 1: size 48 align 16
        y, offset 0

But A.19 is live until the end of function:
  D.1613_7 = (void * restrict) &A.19[0][1]{lb: 1 sz: 1};
  atmp.18.data = D.1613_7;
...
  D.1596_13 = &atmp.18;
...
  pfoo (&ptrtemp.16, 5, D.1596_13, 5);
  y = ptrtemp.16;
  parm.22.dtype = 369;
  parm.22.dim[0].lbound = 1;
  parm.22.dim[0].ubound = 3;
  parm.22.dim[0].stride = 1;
  parm.22.data = &x[0];
  parm.22.offset = -1;
  afoo (&y, &parm.22, 5, 5);
  return;
and thus when it is shared with parm.22 it is overwritten.

I'm using a reduced testcase:
program char_initialiser
  character*5, dimension(3) :: x
  character*5, dimension(:), pointer :: y
  x=(/"is Ja","ne Fo","nda  "/)
  y => pfoo ((/"is Ja","ne Fo","nda  "/))
  call afoo (y, x)
contains
  subroutine afoo(ch1, ch2)
     character*(*), dimension(:) :: ch1, ch2
     if (any(ch1 /= ch2)) call abort ()
  end subroutine afoo
  function pfoo(ch2)
     character*5, dimension(:), target  :: ch2
     character*5, dimension(:), pointer :: pfoo
     pfoo => ch2
  end function pfoo
end program

If this is actually valid Fortran (i.e. the lifetime of
(/"is Ja","ne Fo","nda  "/)
when passed as actual argument to pfoo doesn't end with the return from pfoo),
then it would be a Fortran FE bug - A.19 which is used as the data area for the
atmp.18 temporary whose address is passed to pfoo, is declared in a BLOCK which
starts before atmp.18 definition but doesn't end at the end of function, but
right after y = ptrtemp.16; stmt (and parm.22 correctly starts living just for
the setup of afoo parameters and lives over the actual afoo call.  Thus there
is nothing wrong on the expansion side that it decided to coalesce the two
variables, it is either a FE bug or invalid testcase.

-fdump-tree-origin contains:

...
  {
    integer(kind=8) D.1598;
    character(kind=1)[0:][1:5] * ifm.21;
    struct array1_unknown * D.1596;
    character(kind=1) A.19[3][1:5];
    struct array1_unknown atmp.18;
    static character(kind=1)[1:5] * A.17[3] = {&"is Ja"[1]{lb: 1 sz: 1}, &"ne
Fo"[1]{lb: 1 sz: 1}, &"nda  "[1]{lb: 1 sz: 1}};
    struct array1_unknown ptrtemp.16;

    atmp.18.dtype = 369;
    atmp.18.dim[0].stride = 1;
    atmp.18.dim[0].lbound = 0;
    atmp.18.dim[0].ubound = 2;
    atmp.18.data = (void * restrict) &A.19;
    atmp.18.offset = 0;
    {
      integer(kind=8) S.20;

      S.20 = 0;
      while (1)
        {
          if (S.20 > 2) goto L.5;
          __builtin_memmove ((void *) &(*(character(kind=1)[3][1:5] * restrict)
atmp.18.data)[S.20], (void *) A.17[S.20], 5);
          S.20 = S.20 + 1;
        }
      L.5:;
    }
    D.1596 = &atmp.18;
    ifm.21 = (character(kind=1)[0:][1:5] *) D.1596->data;
    D.1598 = (D.1596->dim[0].ubound - D.1596->dim[0].lbound) + 1;
    pfoo (&ptrtemp.16, 5, D.1596, 5);
    y = ptrtemp.16;
  }
  {
    struct array1_unknown parm.22;

    parm.22.dtype = 369;
    parm.22.dim[0].lbound = 1;
    parm.22.dim[0].ubound = 3;
    parm.22.dim[0].stride = 1;
    parm.22.data = (void *) &x[0];
    parm.22.offset = -1;
    afoo (&y, &parm.22, 5, 5);
  }

[Bug fortran/46325] [4.6 Regression] gfortran.dg/char_initialiser_actual.f90 FAILs with -fstack-protector

[jakub at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=46325

--- Comment #3 from Jakub Jelinek <jakub at gcc dot gnu.org> 2010-11-10 16:11:21 UTC ---
BTW, even 4.4 has the character(kind=1) A.20[3][1:5]; var referenced into the
actual arg to pfoo in a block which doesn't overlap the block of the afoo call.

[Bug fortran/46325] [4.6 Regression] gfortran.dg/char_initialiser_actual.f90 FAILs with -fstack-protector

[burnus at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=46325

Tobias Burnus <burnus at gcc dot gnu.org> changed:

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

--- Comment #4 from Tobias Burnus <burnus at gcc dot gnu.org> 2010-11-11 21:58:42 UTC ---
(In reply to comment #2)
> If this is actually valid Fortran

Short answer: The reduced test program in comment 2 is invalid according to the
Fortran standard. Long answer below.


> program char_initialiser
>   character*5, dimension(3) :: x
>   character*5, dimension(:), pointer :: y
>   x=(/"is Ja","ne Fo","nda  "/)

So far so good. "y" is a pointer and "x" is a nonpointer, nontarget which thus
may not alias.


>   y => pfoo ((/"is Ja","ne Fo","nda  "/))

By itself, it looks valid.


>   function pfoo(ch2)
>      character*5, dimension(:), target  :: ch2
>      character*5, dimension(:), pointer :: pfoo
>      pfoo => ch2
>   end function pfoo

Also this function looks valid as "ch2" is a target (at least in the scope of
"pfoo"). However, as the actual argument associated with "pfoo" (namely "x") is
not a target, the pointer "pfoo" has the pointer associations status
"undefined" after "pfoo" -- that's still valid. Thus:

  y => pfoo ((/"is Ja","ne Fo","nda  "/))

is equivalent to

  y => <undefined pointer>

However, the following line is invalid:
    call afoo (y, x)
as the dummy arguments of "afoo" are not pointers and "y" has the status
undefined.


To put this in some legalize by quoting from Fortran 2008:

"12.5.2.4 Ordinary dummy variables" [...] "If the dummy argument has the TARGET
attribute and the effective argument does not have the TARGET attribute or is
an array section with a vector subscript, any pointers associated with the
dummy argument become undefined when execution of the procedure completes."

And: "7.1.9.2 Type, type parameters, and shape of a primary"
"If the pointer is not associated with a target, it may appear as a primary
only as an actual argument in a reference to a procedure whose corresponding
dummy argument is declared to be a pointer, or as the target in a pointer
assignment statement."

[Bug fortran/46325] [4.6 Regression] gfortran.dg/char_initialiser_actual.f90 FAILs with -fstack-protector

[jakub at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=46325

--- Comment #5 from Jakub Jelinek <jakub at gcc dot gnu.org> 2010-11-11 22:18:35 UTC ---
(In reply to comment #4)
> >   y => pfoo ((/"is Ja","ne Fo","nda  "/))
> 
> However, as the actual argument associated with "pfoo" (namely "x") is
> not a target

Well, the actual argument associated with pfoo here is not x but
(/"is Ja","ne Fo","nda  "/)
but if the same thing applies to it too, then the
gfortran.dg/char_initialiser_actual.f90 testcase is invalid too and thus should
be nuked.

[Bug fortran/46325] [4.6 Regression] gfortran.dg/char_initialiser_actual.f90 FAILs with -fstack-protector

[burnus at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=46325

--- Comment #6 from Tobias Burnus <burnus at gcc dot gnu.org> 2010-11-11 22:32:26 UTC ---
(In reply to comment #5)
> Well, the actual argument associated with pfoo here is not x but
> (/"is Ja","ne Fo","nda  "/)

Well, the effective argument nevertheless does not have the TARGET attribute.
Thus I believe the same argument applies and the test case is invalid.

>  y => <undefined pointer>

Actually, already that line is invalid (per 7.1.9.2).

> but if the same thing applies to it too, then the
> gfortran.dg/char_initialiser_actual.f90 testcase is invalid too and thus should
> be nuked.

Well, not nuked but modified:

@@ -26,3 +26,4 @@ contains
      character*5, dimension(:), pointer :: pfoo
-     pfoo => ch2
+     allocate(pfoo(size(ch2)))
+     pfoo = ch2
   end function pfoo

[Bug fortran/46325] [4.6 Regression] gfortran.dg/char_initialiser_actual.f90 FAILs with -fstack-protector

[burnus at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=46325

--- Comment #7 from Tobias Burnus <burnus at gcc dot gnu.org> 2010-11-11 23:02:10 UTC ---
Author: burnus
Date: Thu Nov 11 23:02:03 2010
New Revision: 166628

URL: http://gcc.gnu.org/viewcvs?root=gcc&view=rev&rev=166628
Log:
2010-11-11  Jakub Jelinek <jakub@redhat.com>
            Tobias Burnus <burnus@net-b.de>

    PR fortran/46325
    * gfortran.dg/char_initialiser_actual.f90: Make test case valid. 

Modified:
    trunk/gcc/testsuite/ChangeLog
    trunk/gcc/testsuite/gfortran.dg/char_initialiser_actual.f90

[Bug fortran/46325] [4.6 Regression] gfortran.dg/char_initialiser_actual.f90 FAILs with -fstack-protector

[burnus at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=46325

Tobias Burnus <burnus at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |RESOLVED
         Resolution|                            |FIXED

--- Comment #8 from Tobias Burnus <burnus at gcc dot gnu.org> 2010-11-11 23:03:43 UTC ---
Close as FIXED.

Thanks Zdenek for the report and thanks Jakub for the analysis.