[Bug fortran/60500] New: Spurious warning on derived type initialization

[Bug fortran/60500] New: Spurious warning on derived type initialization

[jonathan.hogg at stfc dot ac.uk]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=60500

            Bug ID: 60500
           Summary: Spurious warning on derived type initialization
           Product: gcc
           Version: 4.8.1
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: fortran
          Assignee: unassigned at gcc dot gnu.org
          Reporter: jonathan.hogg at stfc dot ac.uk

The following code:

module spurious_warning
   implicit none

   type :: ntype
      integer :: level = 1
   end type ntype
contains
   subroutine sub1(n1, n2, st)
      integer, intent(in) :: n1, n2
      integer, intent(out) :: st

      type(ntype), dimension(:), allocatable :: work1
      integer, dimension(:), allocatable :: work2

      allocate(work1(n1), stat=st)
      if(st.ne.0) return

      allocate(work2(n2), stat=st)
      if(st.ne.0) return
   end subroutine sub1
end module spurious_warning

Produces the following spurious warning:
[user@host]$ gfortran-4.8 -O2 -Wall -c bug.f90
bug.f90: In function ‘sub1’:
bug.f90:12:0: warning: ‘work1.dim[0].ubound’ may be used uninitialized in this
function [-Wmaybe-uninitialized]
       type(ntype), dimension(:), allocatable :: work1
 ^

With the following compiler version:
GNU Fortran (Ubuntu 4.8.1-2ubuntu1~12.04) 4.8.1

Notes:
Removal of -O2 removes the sprurious warning.
Removal of the second allocation removes spurious warning.
Removal of default value in type definition removes spurious warning.

Working theory: The automatic initialization accesses array size as part of
implementation?
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To: gcc-bugs@gcc.gnu.org
Subject: [Bug middle-end/60500] [4.7/4.8/4.9 Regression] Spurious warning on derived type initialization
Date: Tue, 11 Mar 2014 11:14:00 -0000
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http://gcc.gnu.org/bugzilla/show_bug.cgi?id`500

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |NEW
   Last reconfirmed|                            |2014-03-11
          Component|fortran                     |middle-end
            Summary|Spurious warning on derived |[4.7/4.8/4.9 Regression]
                   |type initialization         |Spurious warning on derived
                   |                            |type initialization
     Ever confirmed|0                           |1

--- Comment #1 from Dominique d'Humieres <dominiq at lps dot ens.fr> ---
No warning when compiling the test with r176695 (2011-07-23), warning with
r176935 (2011-07-29).

[Bug middle-end/60500] [4.7/4.8/4.9 Regression] Spurious warning on derived type initialization

[rguenth at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=60500

Richard Biener <rguenth at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Target Milestone|---                         |4.7.4

[Bug fortran/60500] [4.7/4.8/4.9 Regression] Spurious warning on derived type initialization

[rguenth at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=60500

Richard Biener <rguenth at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Keywords|                            |wrong-code
          Component|middle-end                  |fortran

--- Comment #2 from Richard Biener <rguenth at gcc dot gnu.org> ---
The value is used uninitialized on the work1.data == NULL error path:

                  work1.data = (void * restrict) __builtin_malloc (MAX_EXPR
<D.2352, 1>);
                  if (work1.data == 0B)
                    {
                      stat.0 = 5014;
                    }
                }
              }
          }
        if ((logical(kind=4)) __builtin_expect ((integer(kind=8)) (stat.0 ==
0), 1, 33))
          {
            work1.dtype = 297;
            work1.dim[0].lbound = 1;
            work1.dim[0].ubound = (integer(kind=8)) *n1;
            work1.dim[0].stride = 1;
            work1.offset = -1;
          }
        if ((logical(kind=4)) __builtin_expect ((integer(kind=8)) (stat.0 !=
0), 0, 33)) goto L.1;
        L.1:;
        *st = stat.0;
        {
          struct ntype D.2358;
          struct ntype ntype.3;
          integer(kind=8) D.2356;
          integer(kind=8) D.2355;
          integer(kind=8) D.2354;
          struct ntype[0:] * restrict D.2353;

          D.2353 = (struct ntype[0:] * restrict) work1.data;
          D.2354 = work1.offset;
          D.2355 = work1.dim[0].lbound;
          D.2356 = work1.dim[0].ubound;
          ntype.3.level = 1;
          D.2358 = ntype.3;
          {
            integer(kind=8) S.4;

            S.4 = D.2355;
            while (1)
              {
                if (S.4 > D.2356) goto L.3;
                (*D.2353)[S.4 + D.2354] = D.2358;
                S.4 = S.4 + 1;
              }
            L.3:;

possibly the L.1 label is misplaced?  At least the result would crash if
malloc returned NULL.

Frontend wrong-code bug.

[Bug fortran/60500] [4.7/4.8/4.9 Regression] Spurious warning on derived type initialization

[rguenth at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=60500

Richard Biener <rguenth at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Priority|P3                          |P4

[Bug fortran/60500] [4.7/4.8/4.9/4.10 Regression] Spurious warning on derived type initialization

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=60500

Richard Biener <rguenth at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Target Milestone|4.7.4                       |4.8.4

--- Comment #3 from Richard Biener <rguenth at gcc dot gnu.org> ---
The 4.7 branch is being closed, moving target milestone to 4.8.4.

[Bug fortran/60500] [4.8/4.9/5 Regression] Spurious warning on derived type initialization

[jakub at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=60500

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Target Milestone|4.8.4                       |4.8.5

--- Comment #4 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
GCC 4.8.4 has been released.

[Bug fortran/60500] [4.8/4.9/5 Regression] Spurious warning on derived type initialization

[mikael at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=60500

Mikael Morin <mikael at gcc dot gnu.org> changed:

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

--- Comment #5 from Mikael Morin <mikael at gcc dot gnu.org> ---
(In reply to Richard Biener from comment #2)
> possibly the L.1 label is misplaced?  At least the result would crash if
> malloc returned NULL.
> 
Mmh, yes;  it seems L.1 should come after the (default-)initialization of the
just allocated array.
There is nothing that can be done inside gfc_trans_allocate, because
initialization comes from a frontend-generated statement after the allocate
statement (introduced at revision r164305).

[Bug fortran/60500] [4.8/4.9/5/6 Regression] Spurious warning on derived type initialization

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=60500

Richard Biener <rguenth at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Target Milestone|4.8.5                       |4.9.3

--- Comment #6 from Richard Biener <rguenth at gcc dot gnu.org> ---
The gcc-4_8-branch is being closed, re-targeting regressions to 4.9.3.

[Bug fortran/60500] [4.9/5/6 Regression] Spurious warning on derived type initialization

[jakub at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=60500

--- Comment #7 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
GCC 4.9.3 has been released.

[Bug fortran/60500] [4.9/5/6 Regression] Spurious warning on derived type initialization

[jakub at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=60500

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Target Milestone|4.9.3                       |4.9.4