Re: [PATCH] -var-update

[Daniel Jacobowitz <drow at false dot org>]

On Sun, May 21, 2006 at 10:25:24AM +1200, Nick Roberts wrote:
> Yes.  Perhaps my summary isn't precise, but it didn't work.  My patch uses
> value_at while coerce_ref uses value_at_lazy.  The comment says:
> 
>    Call value_at only if the data needs to be fetched immediately;
>    if we can be 'lazy' and defer the fetch, perhaps indefinately, call
>                                                     ^^^^^^^^^^^^
>    value_at_lazy instead.  value_at_lazy simply records the address of
>    the data and sets the lazy-evaluation-required flag.  The lazy flag
>    is tested in the value_contents macro, which is used if and when
>    the contents are actually required.
> 
> value_contents is not a macro (VALUE_CONTENTS used to be one) but a function,
> and doesn't test the lazy flag.

No:

const gdb_byte *
value_contents (struct value *value)
{ 
  return value_contents_writeable (value);
}

gdb_byte *
value_contents_writeable (struct value *value)
{ 
  if (value->lazy)
    value_fetch_lazy (value);
  return value_contents_raw (value);
}

If you take a look at the code you're patching, there should be a
nearby call to value_fetch_lazy or gdb_value_fetch_lazy in each case.
You want to be calling coerce_ref before you do that.  Also, see the
existing calls to release_value?  If you change var->value after that,
you're going to leak memory.

Try calling coerce_ref in here:

      if (gdb_evaluate_expression (var->root->exp, &var->value))
        {
          /* no error */

/* HERE */

          release_value (var->value);
          if (value_lazy (var->value))
            gdb_value_fetch_lazy (var->value);
        }
      else
        var->value = evaluate_type (var->root->exp);


-- 
Daniel Jacobowitz
CodeSourcery