[PATCH] vbscript: Fixed CBool

[Jacek Caban]

On 04/30/14 02:42, Shuai Meng wrote:
> Thank you.
>
>
> 2014-04-30 1:13 GMT+08:00 Piotr Caban <piotr.caban at gmail.com
> <mailto:piotr.caban at gmail.com>>:
>
>     On 04/29/14 17:25, Shuai Meng wrote:
>
>         2014-04-29 22:25 GMT+08:00 Piotr Caban <piotr.caban at gmail.com
>         <mailto:piotr.caban at gmail.com>
>         <mailto:piotr.caban at gmail.com <mailto:piotr.caban at gmail.com>>>:
>
>             No, I mean that you should do something like this:
>             VARIANT v;
>             ...
>             V_VT(&v) = VT_EMPTY;
>             hr = VariantChangeType(..., &v);
>             if(FAILED(hr))
>                  return hr;
>             ...
>
>             if(res)
>                  *res = v;
>             else
>                  VariantClear(&v);
>
>           what will be returned after  *res =  v; or VariantClear(&v); ?
>
>     S_OK, because the function has succeeded.
>
>  
> Then I think this the same as return  VariantChangeType directly. How
> about writing like this:
>
> if(res)
> {
>     V_VT(res) = VT_EMPTY;
>     return VariantChangeType(res, arg, 0, VT_BOOL);
> }
> return S_OK;
>
> Because whether the change succeed or not, VariantChangeType will
> return a value indicating the situation.

Even if res is NULL (meaning that the return value is not used by the
script), the semantic of the code needs to be the same as if it was
used. It's just an optimization and optimizations can't change
semantics. For example:

call CBool("blah")

needs to return an error and you need to perform the conversion to
recognize the error. An other example why this is wrong is if you try to
convert an object. In such case, default value getter needs to be called
(and it's called by VariantChangeType in this case).

Jacek
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