Subj : Re: JS_ValueToString and STRING_TO_JSVAL
To   : Weiyang Zhou
From : Brendan Eich
Date : Fri Aug 12 2005 05:06 pm

Weiyang Zhou wrote:
> If I have the following code, do I have to add str to root too?
> 
>     jsval argv[1];
>     jsval rval;
> 
>     JSString* str = JS_NewString(context, "arg from C", 10);
> 
>     argv[0] = STRING_TO_JSVAL(str);

If argv is as shown above, then yes, you need to register str or argv[0] 
by its address as a root, or do something else to protect the new string 
from GC.

If the above code were in a native function called by the JS engine 
itself, with argv as the fourth parameter (after argc, before rval as 
usual), then no, argv[0] is a local root, as described in that doc I 
linked to before (below).

/be

> 
>     JS_CallFunctionName(context, object, "myfunc", 1, argv, &rval);
> 
> 
> 
> "Brendan Eich" <brendan@meer.net> wrote in message 
> news:42FC29D9.8000408@meer.net...
> 
>>Weiyang Zhou wrote:
>>
>>
>>>What's the purpose of converting argv[i] to str, the assign str back to 
>>>argv[i]? In the end, argv[i] remain the same.
>>
>>
>>Not if !JSVAL_IS_STRING(argv[i]) beforehand.
>>
>>See http://www.mozilla.org/js/spidermonkey/gctips.html for why this is 
>>done in native methods such as Load.
>>
>>/be 
> 
> 
>

.