Subj : Re: how to make C functions return array to js?
To   : netscape.public.mozilla.jseng
From : Oyku Gencay <oyku@sbt.com.tr>
Date : Thu Mar 18 2004 01:28 am

Thanks a lot. I've misssed that document, it helped. Checking and 
returning JS_FALSE helped to catch where the errror was. I should 
already have done it. I'm trying to extend perl binding of SpiderMonkey 
and debugging XS is like hell. Now I correctly got arrays going from-to 
perl from-to JS, now I'll try binding perl hashes to js objects.

Cheers,
Oyku

Brendan Eich wrote:
> Oyku Gencay wrote:
> 
>> Hi folks,
>>
>> How can I return an array to javascript from a C function? I have a 
>> native C function which returns an array.  When I run this I get a 
>> segfault.
> 
> 
> Where?  What stack?
> 
>> The function code is;
>>
>> static JSBool
>> TestingArraysAsReturn(JSContext *cx, JSObject *obj, uintN argc,
>>     jsval *argv, jsval *rval) {
>>
>> JSObject *js_array ;
>> js_array = JS_NewArrayObject(cx,0,NULL);
>> for (i = 1 ; i <= 5 ; ++i) {
>>     jsval *js;
>>     js = STRING_TO_JSVAL(JS_NewStringCopyZ(cx, "testing"));
> 
> 
> Bug: you are assigning a jsval to a jsval* here, surely your compiler 
> warned you?
> 
> You want jsval v = STRING_TO_JSVAL(str); where str is set to the result 
> of JS_NewStringCopyZ, and you test that result against null first, 
> returning false to handle out-of-memory errors.
> 
>>     JS_SetElement(cx,js_array,i,js);
> 
> 
> So you want &v, not js, here.
> 
>> }
>> *rval = OBJECT_TO_JSVAL(js_array);
>> return JS_TRUE;
>> }
> 
> 
> Please also read http://www.mozilla.org/js/spidermonkey/gctips.html, 
> note the need to root as you go.  Storing *rval late is not good -- what 
> if the GC ran from one of the JS_NewStringCopyZ calls?
> 
> /be

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