[webkit-dev] JSC: Callback functions returning exception, what should be the JSValueRef return?

Oliver Hunt oliver at apple.com
Tue Aug 11 11:22:57 PDT 2009

On Aug 11, 2009, at 11:13 AM, Brian Barnes wrote:

> Darin Adler wrote:
>> The design is that the return value is ignored. In theory, you can  
>> safely return anything, even a garbage pointer.
>>    -- Darin
> Just so I get the concept (how exceptions are handled is one of the  
> places that is completely different in Spidermonkey so it's one of  
> the biggest hurdles for me) -- when the class based SET property or  
> a STATIC FUNCTION is called, it detects when an exception is thrown  
> by my replacement of the JSValueRef *exception, correct?  There's  
> nothing else I have to trigger (in SM you have to implicitly trigger  
> by calling a function.)
> Also, when an exception I create reaches the top (where I originally  
> called into the script with JSObjectCallAsFunction) how can I  
> determine the line number where the exception happened?  I can't  
> seem to find this in the docs either.  If I have to do this when I  
> create the exception, that is also fine.

Alas there isn't really a nice way to determine where an exception  
occurred using the API, but through convention any object thrown gets  
a line number and sourceURL property attached to it.  When you tell  
JSC to execute a script you provide the initial line number and the  
url that it will attach to the exception.

You can then use normal JSC APIs to get those properties off the  
exception object.


> [>] Brian
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