Re: [MI] lvalues and variable_editable

[Vladimir Prus <ghost@cs.msu.su>]

Nick Roberts wrote:

> --- 1747,1752 ----
> *************** value_get_print_value (struct value *val
> *** 1799,1804 ****
> --- 1778,1808 ----
> return thevalue;
> }
> 
> +
> + static int
> + variable_editable_pv (struct varobj *var)

Can we probably use "varobj_editable_pv". Using
varobj in some places, and "variable" in others
makes for confusing code.

> + {
> +   struct expression *exp;
> +   struct value *value;
> +
> +   if (CPLUS_FAKE_CHILD (var))
> +     return 0;
> +
> +   if (is_root_p (var))
> +     {
> +       if (!gdb_evaluate_expression (var->root->exp, &value))
> +       {
> +         /* We cannot proceed without a valid expression. */
> +         xfree (exp);
> +         return 0;
> +       }

Why do you evaluate this? The expression should already be
evaluated when creating varobj. So, using var->value should
be sufficient.

Also, why is_root_p check? It is possible to create varobj for
an expression the creates rvalue of structure type. The children of 
such varobj won't be lvalues, and won't be editable, but this code
won't catch this case.


> *************** varobj_value_is_changeable_p (struct var
> *** 1819,1837 ****
> --- 1822,1842 ----
> 
> type = get_value_type (var);
> 
> +
> switch (TYPE_CODE (type))
> {
> case TYPE_CODE_STRUCT:
> case TYPE_CODE_UNION:
> case TYPE_CODE_ARRAY:
> !     case TYPE_CODE_FUNC:
> !     case TYPE_CODE_METHOD:
> !       return 0;

In current gdb, assuming this declaration:

        void (*fp)();

I can create varobj for *fp:

        -var-create V * *fp

and V will be updated if fp changes. With your patch,
I get this:

        -var-create V * *fp
        ~"varobj.c:2180: internal-error: c_value_of_variable: Assertion `varobj_value_is_changeable_p (var)' failed.\n"
        ~"A problem internal to GDB has been detected,\n"
        ~"further debugging may prove unreliable.\n"
        ~"Quit this debugging session? (y or n) "


So, probably TYPE_CODE_FUNC should be handled in variable_editable_p.
I'm not sure about TYPE_CODE_METHOD -- I don't know how to construct
an object of that type using any possible expression.

- Volodya