[PATCH] Fix GC PCH bug in dwarf2out.c (PR c++/79821)

[Jason Merrill]

OK.

On Mon, Mar 6, 2017 at 3:56 PM, Jakub Jelinek <jakub@redhat.com> wrote:
> Hi!
>
> gengtype.c considers all GC arrays with char/unsigned char/signed char
> element type as strings, for which it computes size e.g. in gt_pch_note_object
> using:
>   if (note_ptr_fn == gt_pch_p_S)
>     (*slot)->size = strlen ((const char *)obj) + 1;
>   else
>     (*slot)->size = ggc_get_size (obj);
> That is really undesirable if the array is actually a collection of random
> bytes rather than a NUL terminated string - then we can either compute
> smaller size if there are zeros in the array, or if unlucky enough and there
> are no zero bytes until end of mapped region, segfault.
>
> Fixed by avoiding the gt_pch_*_S handling by using void * pointer instead.
>
> Bootstrapped/regtested on x86_64-linux and i686-linux, and Rainer has kindly
> tested it on sparc*-solaris* where it caused bootstrap issues.  Ok for
> trunk?
>
> 2017-03-06  Jakub Jelinek  <jakub@redhat.com>
>
>         PR c++/79821
>         * dwarf2out.h (dw_vec_const): Change array type from unsigned char *
>         to void * for PCH reasons.
>         * dwarf2out.c (output_loc_operands, output_die): Cast
>         v.val_vec.array to unsigned char *.
>
> --- gcc/dwarf2out.h.jj  2017-01-01 12:45:37.000000000 +0100
> +++ gcc/dwarf2out.h     2017-03-06 12:13:48.809589411 +0100
> @@ -163,7 +163,7 @@ enum dw_val_class
>  /* Describe a floating point constant value, or a vector constant value.  */
>
>  struct GTY(()) dw_vec_const {
> -  unsigned char * GTY((atomic)) array;
> +  void * GTY((atomic)) array;
>    unsigned length;
>    unsigned elt_size;
>  };
> --- gcc/dwarf2out.c.jj  2017-02-25 09:17:44.000000000 +0100
> +++ gcc/dwarf2out.c     2017-03-06 12:15:52.668958458 +0100
> @@ -2020,7 +2020,7 @@ output_loc_operands (dw_loc_descr_ref lo
>                 elt_size /= 2;
>                 len *= 2;
>               }
> -           for (i = 0, p = val2->v.val_vec.array;
> +           for (i = 0, p = (unsigned char *) val2->v.val_vec.array;
>                  i < len;
>                  i++, p += elt_size)
>               dw2_asm_output_data (elt_size, extract_int (p, elt_size),
> @@ -2273,7 +2273,7 @@ output_loc_operands (dw_loc_descr_ref lo
>                   elt_size /= 2;
>                   len *= 2;
>                 }
> -             for (i = 0, p = val2->v.val_vec.array;
> +             for (i = 0, p = (unsigned char *) val2->v.val_vec.array;
>                    i < len;
>                    i++, p += elt_size)
>                 dw2_asm_output_data (elt_size, extract_int (p, elt_size),
> @@ -10105,7 +10105,7 @@ output_die (dw_die_ref die)
>                 elt_size /= 2;
>                 len *= 2;
>               }
> -           for (i = 0, p = a->dw_attr_val.v.val_vec.array;
> +           for (i = 0, p = (unsigned char *) a->dw_attr_val.v.val_vec.array;
>                  i < len;
>                  i++, p += elt_size)
>               dw2_asm_output_data (elt_size, extract_int (p, elt_size),
>
>         Jakub