Subj : Re: Help with embedding spidermonkey please!!!
To   : netscape.public.mozilla.jseng
From : Brendan Eich <brendan@meer.net>
Date : Sat Nov 08 2003 10:23 am

Georg Maaß wrote:

> Blacksage wrote:
>
>> ScriptEngine::ScriptEngine()
>> {
>>  cout << "Contstructor Start" << endl;
>>
>>  m_JSRunTime = NULL;
>>  m_JSContext = NULL;
>>  m_GlobalObject = NULL;
>>
>>  m_JSRunTime = JS_NewRuntime(4 * 1024 * 1024);
>>  m_JSContext = JS_NewContext(m_JSRunTime,  8 * 1024);
>>
>>  JSClass globalClass =
>
>
> naming a local variable globalClass does not make it global. After the 
> ScriptEngine constructor finished its work, the global object no 
> longer exists, because it was a local object. Define it as global 
> variable of the application [awful] or as member of the ScriptEngine 
> class [more flexible]. Do not define it as local variable of the 
> ScriptEngine constructor. This must crash or at least cause 
> unpredictionable results.


Thanks, Georg.  I wanted to add an explanation of why this is so: the JS 
engine uses the *address* of each JSClass as the unique-per-class (among 
all runtimes!) [[Class]] internal property value (see ECMA-262).  This 
internal property of all native objects tells us what class each belongs 
to, via pointer comparison or, more frequently, via calls through 
clasp->getProperty, etc. (or clasp->getObjectOps()->...).

Make each JSClass static and you'll be happy.

/be

.