[Patch, gfortran] PR26257 - Segmentation fault, on function call with assumed shape array parameter

[Paul Thomas]

Paul Thomas wrote:

Ping!

Original is found on http://gcc.gnu.org/ml/fortran/2006-02/msg00553.html.

The patch has evolved slightly, although the principle is the same.  
Instead of testsing for the symbol possessing a namespace, the caller 
explicitly demands that the data and offset fields not be filled, 
through a new bitfield in gfc_se.

Again, regtested on FC3/Athlon.

Paul

> :ADDPATCH fortran:
>
> With reference to the attached testcase, the seg fault due to the 
> function being use associated - the segfault occurs via the route 
> gfc_conv_intrinsic_size => gfc_conv_expr_descriptor => 
> gfc_build_addr_expr, which is needed to calculate the potential offset 
> between the full array and the actual argument of SIZE, which is 
> assumed to be an array section.  However, seen from the main program, 
> the address of a dummy argument of a module procedure is not the most 
> readily available thing in the world - in fact, it has already gone 
> out of scope.
>
> Happily, SIZE does not need the offset or the data, come to that.  
> Thus a patch, in which we check that the symbol belongs to a namespace 
> before trying to provoke a segfault, judiciously deposited in 
> gfc_conv_expr_descriptor, does the job.  This patch is attached, 
> together with a testsuite version of the reduced PR testcase.
>
> Regtested on FC3/Athlon.
>
> OK for mainline and 4.1, when reopened?
>
> Paul
>
> 2006-02-29  Paul Thomas  <pault@gcc.gnu.org>
>
>    PR fortran/26257
>    * trans-array.c (gfc_conv_expr_descriptor): Exclude calculation of 
> the offset
>    for arrays without a namespace - ie. module procedure dummies.
>
> 2006-02-29  Paul Thomas  <pault@gcc.gnu.org>
>
>    PR fortran/26257
>    gfortran.dg/auto_char_len_3.f90: New test
>
>
>
>------------------------------------------------------------------------
>
>Index: gcc/fortran/trans-array.c
>===================================================================
>*** gcc/fortran/trans-array.c	(revision 111450)
>--- gcc/fortran/trans-array.c	(working copy)
>*************** gfc_conv_expr_descriptor (gfc_se * se, g
>*** 3789,3797 ****
>--- 3789,3800 ----
>    tree offset;
>    int full;
>    gfc_ref *ref;
>+   gfc_symbol *sym;
>  
>    gcc_assert (ss != gfc_ss_terminator);
>  
>+   sym = expr->expr_type == EXPR_VARIABLE ? expr->symtree->n.sym : NULL;
>+ 
>    /* TODO: Pass constant array constructors without a temporary.  */
>    /* Special case things we know we can pass easily.  */
>    switch (expr->expr_type)
>*************** gfc_conv_expr_descriptor (gfc_se * se, g
>*** 4143,4154 ****
>  	  dim++;
>  	}
>  
>!       /* Point the data pointer at the first element in the section.  */
>!       tmp = gfc_conv_array_data (desc);
>!       tmp = build_fold_indirect_ref (tmp);
>!       tmp = gfc_build_array_ref (tmp, offset);
>!       offset = gfc_build_addr_expr (gfc_array_dataptr_type (desc), tmp);
>!       gfc_conv_descriptor_data_set (&loop.pre, parm, offset);
>  
>        if (se->direct_byref)
>  	{
>--- 4146,4160 ----
>  	  dim++;
>  	}
>  
>!       if (!(sym && !sym->ns && !se->direct_byref))
>! 	{
>! 	  /* Point the data pointer at the first element in the section.  */
>! 	  tmp = gfc_conv_array_data (desc);
>! 	  tmp = build_fold_indirect_ref (tmp);
>! 	  tmp = gfc_build_array_ref (tmp, offset);
>! 	  offset = gfc_build_addr_expr (gfc_array_dataptr_type (desc), tmp);
>! 	  gfc_conv_descriptor_data_set (&loop.pre, parm, offset);
>! 	}
>  
>        if (se->direct_byref)
>  	{
>  
>
>------------------------------------------------------------------------
>
>! { dg-do run }
>! Test the fix for PR26257, in which the implicit reference to
>! chararray in the main program call of chararray2string would
>! cause a segfault in gfc_build_addr_expr.
>!
>! Based on the reduced testcase in the PR.
>module chtest
>contains
>  function chararray2string(chararray) result(text)
>    character(len=1), dimension(:) :: chararray    ! input
>    character(len=size(chararray, 1)) :: text      ! output
>    do i = 1,size(chararray,1)
>      text(i:i) = chararray (i)
>    end do
>  end function chararray2string
>end module chtest
>program TestStringTools
>  use chtest
>  character(len=52)               :: txt
>  character(len=1), dimension(52) :: chararr = &
>        (/(char(i+64),char(i+96), i = 1,26)/)
>  txt = chararray2string(chararr)
>  if (txt .ne. "AaBbCcDdEeFfGgHhIiJjKkLlMmNnOoPpQqRrSsTtUuVvWwXxYyZz") &
>        call abort ()
>end program TestStringTools
>  
>

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