Re: Trivial fix in value_sub

[Jim Ingham <jingham at apple dot com>]

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