2002-05-11 Daniel Jacobowitz <drow@mvista.com>

[deliverable/binutils-gdb.git] / gdb / valarith.c

diff --git a/gdb/valarith.c b/gdb/valarith.c
index c3d537a192353c15a76305cf1de5cf2d33b2d152..cc067cb4b518f7fc0f0755f5422235a62833cb50 100644 (file)
--- a/gdb/valarith.c
+++ b/gdb/valarith.c
@@ -43,12 +43,50 @@ static struct value *value_subscripted_rvalue (struct value *, struct value *, i
 void _initialize_valarith (void);
 \f
 
+/* 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;
-  register int len;
+  LONGEST sz;
   struct type *type1, *type2, *valptrtype;
 
   COERCE_NUMBER (arg1);
@@ -77,12 +115,12 @@ value_add (struct value *arg1, struct value *arg2)
          valint = arg1;
          valptrtype = type2;
        }
-      len = TYPE_LENGTH (check_typedef (TYPE_TARGET_TYPE (valptrtype)));
-      if (len == 0)
-       len = 1;                /* For (void *) */
+
+      sz = find_size_for_pointer_math (valptrtype);
+
       retval = value_from_pointer (valptrtype,
                                   value_as_address (valptr)
-                                  + (len * value_as_long (valint)));
+                                  + (sz * value_as_long (valint)));
       VALUE_BFD_SECTION (retval) = VALUE_BFD_SECTION (valptr);
       return retval;
     }
@@ -104,7 +142,8 @@ value_sub (struct value *arg1, struct value *arg2)
       if (TYPE_CODE (type2) == TYPE_CODE_INT)
        {
          /* pointer - integer.  */
-         LONGEST sz = TYPE_LENGTH (check_typedef (TYPE_TARGET_TYPE (type1)));
+         LONGEST sz = find_size_for_pointer_math (type1);
+
          return value_from_pointer (type1,
                                     (value_as_address (arg1)
                                      - (sz * value_as_long (arg2))));