[Bug fortran/45128] New: Segmentation fault with -fwhole-file

[Bug fortran/45128] New: Segmentation fault with -fwhole-file

[dominiq at lps dot ens dot fr]

The following code (from pr40737)

! { dg-do compile }
module testmod
  implicit none
  type VARIABLES_MAILLE
      real :: cell_var
  end type VARIABLES_MAILLE
  type (VARIABLES_MAILLE), pointer, dimension( :) :: Hydro_vars
  real, pointer, dimension(:) :: Ro
end module testmod

program TF_AD_SPLITTING_DRIVER_PLANE
  use testmod
  implicit none
  Ro => Hydro_vars(1:2)%cell_var
end program

gives a Segmentation fault when compiled with -fwhole-file. The backtrace is

Program received signal EXC_BAD_ACCESS, Could not access memory.
Reason: KERN_INVALID_ADDRESS at address: 0x0000000000000018
0x00000001000d1d38 in gfc_trans_pointer_assignment (expr1=0x14191a3f0,
expr2=0x141919960) at ../../work/gcc/fortran/trans-expr.c:4768
4768                  gfc_add_modify (&lse.post, GFC_DECL_SPAN(decl), tmp);
(gdb) bt
#0  0x00000001000d1d38 in gfc_trans_pointer_assignment (expr1=0x14191a3f0,
expr2=0x141919960) at ../../work/gcc/fortran/trans-expr.c:4768
#1  0x00000001000a9ae6 in trans_code (code=0x14191a960, cond=0x0) at
../../work/gcc/fortran/trans.c:1109
#2  0x00000001000c7bd2 in gfc_generate_function_code (ns=<value temporarily
unavailable, due to optimizations>) at ../../work/gcc/fortran/trans-decl.c:4495
#3  0x000000010006b0bd in gfc_parse_file () at
../../work/gcc/fortran/parse.c:4253
#4  0x00000001000a496c in gfc_be_parse_file (set_yydebug=<value temporarily
unavailable, due to optimizations>) at ../../work/gcc/fortran/f95-lang.c:241
#5  0x00000001006990da in toplev_main (argc=2, argv=0x7fff5fbfd9d8) at
../../work/gcc/toplev.c:945
#6  0x0000000100001154 in start ()


-- 
           Summary: Segmentation fault with -fwhole-file
           Product: gcc
           Version: 4.6.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: fortran
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: dominiq at lps dot ens dot fr


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=45128

[Bug fortran/45128] Segmentation fault with -fwhole-file for subref_array_pointer

[burnus at gcc dot gnu dot org]

------- Comment #1 from burnus at gcc dot gnu dot org  2010-07-29 14:44 -------
Carry over the comment from PR 45125, where I had posted it initially (and
accidentally).

The segfault occurs for:

l.4768             gfc_add_modify (&lse.post, GFC_DECL_SPAN(decl), tmp);

It seems as if GFC_DECL_SPAN(decl) access a NULL pointer. That's
  decl->decl_common.lang_specific->span
where lang_specific == NULL.

While the dump has:

tf_ad_splitting_driver_plane ()
{
  extern integer(kind=8) span.0 = 0;
  [...]
    span.0 = 4;

the "span" variable does not really exist globally but is only created when
needed, cf.
http://gcc.gnu.org/git/?p=gcc.git;a=blob;f=gcc/fortran/trans-decl.c;hb=HEAD#l1243

gfc_get_symbol_decl:

1243   else if (sym->attr.subref_array_pointer)
1245       /* We need the span for these beasts.  */
1246       gfc_allocate_lang_decl (decl);

1249   if (sym->attr.subref_array_pointer)
1261       GFC_DECL_SPAN (decl) = span;

If one now recycles the definition for the array descriptor "desc" this
information is not present. I think the real solution is the new array
descriptor. I do not know how to fix this otherwise - except by always
generating a span variable.

Paul - any progress from the array-descriptor front?


-- 

burnus at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |pault at gcc dot gnu dot org
             Status|UNCONFIRMED                 |NEW
     Ever Confirmed|0                           |1
           Keywords|                            |ice-on-valid-code
   Last reconfirmed|0000-00-00 00:00:00         |2010-07-29 14:44:16
               date|                            |
            Summary|Segmentation fault with -   |Segmentation fault with -
                   |fwhole-file                 |fwhole-file  for
                   |                            |subref_array_pointer


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=45128

[Bug fortran/45128] Segmentation fault with -fwhole-file for subref_array_pointer

[paul dot richard dot thomas at gmail dot com]

------- Comment #2 from paul dot richard dot thomas at gmail dot com  2010-08-09 10:50 -------
Subject: Re:  Segmentation fault with -fwhole-file for 
        subref_array_pointer

Dear Tobias,

> If one now recycles the definition for the array descriptor "desc" this
> information is not present. I think the real solution is the new array
> descriptor. I do not know how to fix this otherwise - except by always
> generating a span variable.

This has occurred to me more than once!

>
> Paul - any progress from the array-descriptor front?

Yes, I made a small start whilst on vacation.  I have embarked on the
first step of the project, which is to add to the existing dimension
triplet the stride measure (sm) and extent fields.  On top of that, I
added an extra field to the descriptor itself, which does nothing but
uncover all the accesses to the descriptor fields that do not use the
ABI in trans-array.c.  I just reached the stage of plugging all the
segfaults arising from the latter.  The next step is to evaluate the
sm and extent fields, in parallel to the stride and upper fields, just
to check all is well.  Then will come the crucial step of using the
new fields for evaluation of array references.  I suspect that there
will be a substantial performance hit in the scalarizer and problems
with the library, both of which will require time to fix.  Then, the
stride and upper fields can be taken away.  Finally, all the extra
fields can be added to the descriptor.

I will have some time to work on this next week.

Cheers

Paul


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=45128

[Bug fortran/45128] Segmentation fault with -fwhole-file for subref_array_pointer

[jvdelisle at gcc dot gnu dot org]

------- Comment #3 from jvdelisle at gcc dot gnu dot org  2010-08-09 17:18 -------
Paul, can you send me a preview of the new descriptor structure so I can be
planning the internal unit I/O impacts if any.


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=45128

[Bug fortran/45128] Segmentation fault with -fwhole-file for subref_array_pointer

[paul dot richard dot thomas at gmail dot com]

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------- Comment #4 from paul dot richard dot thomas at gmail dot com  2010-08-15 16:32 -------
Subject: Re:  Segmentation fault with -fwhole-file for subref_array_pointer

Dear Jerry,


> ------- Comment #3 from jvdelisle at gcc dot gnu dot org  2010-08-09 17:18 -------
> Paul, can you send me a preview of the new descriptor structure so I can be
> planning the internal unit I/O impacts if any.

This is something that we will all have to agree.  At present, my work
is entirely devoted to getting the new dimension triplet working and
sorting out the side-effects of adding one or more new fields to the
descriptor. It's a real dog....... Still, I have four evenings that I
can devote to it this week :-)

Cheers

Paul


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=45128