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Re: Changing the "enclosing_type" of a value structure
- To: Andrew Cagney <ac131313 at cygnus dot com>
- Subject: Re: Changing the "enclosing_type" of a value structure
- From: Jim Ingham <jingham at apple dot com>
- Date: Mon, 14 Aug 2000 11:32:07 -0700
- CC: <gdb at sources dot redhat dot com>
Also sprach Andrew Cagney:
> Jim Ingham wrote:
>
>> /* If we have the full object, but for some reason the enclosing
>> type is wrong, set it *//* pai: FIXME -- sounds iffy */
>
> I like the comment...
Yeah, this is the sort of thing that really warms your heart after you have
spent a couple of days chasing down memory corruption...
>
>> return (value_ptr) xrealloc (val, sizeof (struct type)
>> + TYPE_LENGTH (new_type));
>
> Should it simply refuse to expand a type? That extra data becomes
> undefined in general?
>
The sketch I sent in the last note was not right. You have to change the
lazy flag - which will take care of your objection (though in all the code
paths I could see the data had not been read when this switch was done) -
and you have to stick the new value back into the value chain, or the old
value will get freed, which is BAD. Here is another - better - version.
This one seems to work pretty well.
value_ptr
value_change_enclosing_type (value_ptr val, struct type *new_encl_type)
{
/* If you follow the code, most of the time that this function
is called, the types are the same... So shortcut this case. */
if (new_encl_type == VALUE_ENCLOSING_TYPE (val))
{
return val;
}
else if (TYPE_LENGTH (new_encl_type)
> TYPE_LENGTH (VALUE_ENCLOSING_TYPE (val)))
{
value_ptr old_val = val;
register value_ptr prev;
val = (value_ptr) xrealloc (old_val, sizeof (struct value)
+ TYPE_LENGTH (new_encl_type));
/* We have to make sure this ends up in the same place in the value
chain as the original copy, so it's clean-up behavior is the same.
If the value has been released, this is a waste of time, but there
is no way to tell that in advance, so... */
if (old_val != all_values)
{
for (prev = all_values; prev != NULL; prev = prev->next)
{
if (prev->next == old_val)
{
prev->next = val;
break;
}
}
}
}
VALUE_ENCLOSING_TYPE (val) = new_encl_type;
/* If we had to change the enclosing type, the data in the value
is no longer good. Setting lazy back to 1 will force it to be
reread. */
VALUE_LAZY (val) = 1;
return val;
}
Jim
--
Jim Ingham jingham@apple.com
Apple Computer