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From "Alexey Varlamov" <alexey.v.varla...@gmail.com>
Subject Re: [vmi] Retrieving system properties (was: Re: [classlib][luni] update for bootstrapClassPath causes regression on DRL VM)
Date Thu, 14 Dec 2006 10:07:16 GMT
2006/12/13, Geir Magnusson Jr. <geir@pobox.com>:
>
>
> Gregory Shimansky wrote:
> > Alexey Varlamov wrote:
> >> 2006/12/13, Gregory Shimansky <gshimansky@gmail.com>:
> >>> Tim Ellison wrote:
> >>> > Alexey Varlamov wrote:
> >>> >> Is there any reason to distinguish these cases? I suppose no, then
> >>> >> returned NULL is fine.
> >>> >
> >>> > Maybe we do, i.e. where there is no value "-Dfoobar".  So perhaps we
> >>> > need to say that GetSystemProperty returns VMI_ERROR_NONE and sets
the
> >>> > the *valuePtr to NULL if there is no value; and returns a
> >>> > VMI_ERROR_NOT_FOUND if the property is undefined.
> >>>
> >>> Now I am confused. What is the difference between a property which has
> >>> no value and an undefined property?
> >>
> >> Some properties may act as a flag, e.g. -Djava.lang.SecurityManager.
> >> However, they have empty value in RI (interestingly, DRLVM ignores
> >> such arguments - must be a bug). So NULL value is still enough to
> >> indicate no such property is set.
> >
> > I don't see how we can distinguish such properties in drlvm using just
> > one function get_property(const char*, PropertyTable). It either returns
> > a valid pointer to the property string value or NULL.
> >
> > Also empty value in my understanding is still a valid value "".
>
> yes, but NULL and "" are still two different things.  I suspect that we
> should simply modify the API to have return code :
>
>    int status = get_property(const char* key, const char **value, table)
>
> so you can see if the key exists if you care.  You may not care.
>
> Or, add a new method
>
>   int status = has_key(char *key);
>
> depending on whatever criterion we use for this API.

There is such API:
VMEXPORT int is_property_set(const char* key, PropertyTable table_number);
Actually, NULL property values are allowable in drlvm just
historically, I see no strong reason to retain this.

>
> geir
>
> >
>
>

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