Re: Trivial fix in value_sub

[Jim Blandy <jimb@redhat.com>]

Great.  Please commit that.

Jim Ingham <jingham@apple.com> writes:

> Okay, how 'bout:
> 
> 2002-04-04  Jim Ingham  <jingham@apple.com>
> 
>          * valarith.c (find_size_for_pointer_math): New function,
> either returns
> 	   the size for a pointer's target, returns 1 for void *, or errors for
>          incomplete types.
>          (value_add, value_sub): use find_size_for_pointer_math.
> 
> Index: valarith.c
> ===================================================================
> RCS file: /cvs/src/src/gdb/valarith.c,v
> retrieving revision 1.14
> diff -c -w -p -r1.14 valarith.c
> *** valarith.c  2002/03/27 21:35:35     1.14
> --- valarith.c  2002/04/04 23:05:12
> *************** static struct value *value_subscripted_r
> *** 43,54 ****
>    void _initialize_valarith (void);
> 
> 
> 
>    struct value *
>    value_add (struct value *arg1, struct value *arg2)
>    {
>      struct value *valint;
>      struct value *valptr;
> !   register int len;
>      struct type *type1, *type2, *valptrtype;
> 
>      COERCE_NUMBER (arg1);
> --- 43,92 ----
>    void _initialize_valarith (void);
> 
> 
> 
> + /* Given a pointer, return the size of its target.
> +    If the pointer type is void *, then return 1.
> +    If the target type is incomplete, then error out.
> +    This isn't a general purpose function, but just a
> +    helper for value_sub & value_add.
> + */
> +
> + static LONGEST
> + find_size_for_pointer_math (struct type *ptr_type)
> + {
> +   LONGEST sz = -1;
> +   struct type *ptr_target;
> +
> +   ptr_target = check_typedef (TYPE_TARGET_TYPE (ptr_type));
> +
> +   sz = TYPE_LENGTH (ptr_target);
> +   if (sz == 0)
> +     {
> +       if (TYPE_CODE (ptr_type) == TYPE_CODE_VOID)
> +       sz = 1;
> +       else
> +       {
> +         char *name;
> +
> +         name = TYPE_NAME (ptr_target);
> +         if (name == NULL)
> +           name = TYPE_TAG_NAME (ptr_target);
> +         if (name == NULL)
> +           error ("Cannot perform pointer math on incomplete types, "
> +                  "try casting to a known type, or void *.");
> +         else
> +           error ("Cannot perform pointer math on incomplete type
> \"%s\", "
> +                  "try casting to a known type, or void *.", name);
> +       }
> +     }
> +   return sz;
> + }
> +
>    struct value *
>    value_add (struct value *arg1, struct value *arg2)
>    {
>      struct value *valint;
>      struct value *valptr;
> !   LONGEST sz;
>      struct type *type1, *type2, *valptrtype;
> 
>      COERCE_NUMBER (arg1);
> *************** value_add (struct value *arg1, struct va
> *** 77,88 ****
>            valint = arg1;
>            valptrtype = type2;
>          }
> !       len = TYPE_LENGTH (check_typedef (TYPE_TARGET_TYPE
> (valptrtype)));
> !       if (len == 0)
> !       len = 1;                /* For (void *) */
>          retval = value_from_pointer (valptrtype,
>                                     value_as_address (valptr)
> !                                  + (len * value_as_long (valint)));
>          VALUE_BFD_SECTION (retval) = VALUE_BFD_SECTION (valptr);
>          return retval;
>        }
> --- 115,126 ----
>            valint = arg1;
>            valptrtype = type2;
>          }
> !
> !       sz = find_size_for_pointer_math (valptrtype);
> !
>          retval = value_from_pointer (valptrtype,
>                                     value_as_address (valptr)
> !                                  + (sz * value_as_long (valint)));
>          VALUE_BFD_SECTION (retval) = VALUE_BFD_SECTION (valptr);
>          return retval;
>        }
> *************** value_sub (struct value *arg1, struct va
> *** 104,110 ****
>          if (TYPE_CODE (type2) == TYPE_CODE_INT)
>          {
>            /* pointer - integer.  */
> !         LONGEST sz = TYPE_LENGTH (check_typedef (TYPE_TARGET_TYPE
> (type1)));
>            return value_from_pointer (type1,
>                                       (value_as_address (arg1)
>                                        - (sz * value_as_long (arg2))));
> --- 142,149 ----
>          if (TYPE_CODE (type2) == TYPE_CODE_INT)
>          {
>            /* pointer - integer.  */
> !         LONGEST sz = find_size_for_pointer_math (type1);
> !
>            return value_from_pointer (type1,
>                                       (value_as_address (arg1)
>                                        - (sz * value_as_long (arg2))));
> 
> Jim
> 
> >
> > Jim Ingham <jingham@apple.com> writes:
> >> Okay, so to be consistent, I throw errors in both value_add &
> >> value_sub.  How about this:
> >
> > Superb!  Could you move the "fix up my size or report an error" code
> > into a function instead of repeating it?
> >
> --
> Jim Ingham                                   jingham@apple.com
> Developer Tools - gdb
> Apple Computer