in reply to Re^16: Perl crash during perl_clone
in thread Perl crash during perl_clone

Hi BrowserUk,

Thanks again for the response. I will try tomorrow, but I'm also fairly positive, these versions will work for me too..Fundamentally, there seems no issue with callbacks perse, as long as I comply with your comment that.

If I try to pass the callback addresses by code-reference instead of name, I too get traps. I don't know why, so don't do that.

Although, it is strange why the code-ref way works, reliably, for one of my callbacks registered this way.

I had tried, but the SWIG typemaps I have currently did not allow the 'modulename:subname' format to register the callbacks. I'll have to dig into that more. Will hopefully have good news to share tomorrow!

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Re^18: Perl crash during perl_clone
by BrowserUk (Patriarch) on Nov 08, 2010 at 15:42 UTC
    I had tried, but the SWIG typemaps I have currently did not allow the 'modulename:subname' format to register the callbacks.

    I don't understand this. The SWIG stuff wraps the registering of the CCB, not the PCB.

    So you "register" the PCB--by storing the SV* you pass into your code. You then call that stored SV* (using call_sv()) when the SWIG stuff calls back you CCB.

    I agree that call_sv() should handle coderefs (according to the documentation; I even think I've done it in the past on 5.8x era perls), but every time I've tried it recently, it falls in a heap with coderefs (with or without threads involved), and works as advertised with a function name. So I stick with the latter. It does mean you have to name the callbacks rather than use anonymous subs or blocks, but that is an acceptable limitation (for me).

    I having trouble understanding why you cannot do the same?

    Examine what is said, not who speaks -- Silence betokens consent -- Love the truth but pardon error.
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      I may have made some other mistake when I tried the SWIG wrapper experiment.

      Its quite late in the night here and I hope I'm not celebrating too early: I think I figured out the cause for the seg-faults in the sample code (myModule version) and my real project.

      The problem seems to be that the \&module:sub syntax is somehow a temporary reference and was out of scope by the time my callback was invoked. The reason it worked in one of my callbacks was sheer coincidence: a scalar that was holding a reference to the sub was still in scope when the callback is called.

      In the RegisterCB function, by doing a newSVsv() and then using that new SV as the PCB always seem to keep the reference in scope/valid when the PCB is called. This newSVsv() was in the first version of my code that did the perl_clone, but I had removed it along with a bunch of other code, thinking it was not necessary.

      I'll try to reconfirm tomorrow when I'm more awake :-) Let me know if it works for you and if it makes sense.

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        Let me know if it works for you and if it makes sense.

        Sorry, you lost me there ) I can't see where you could put newSVsv() in RegisterCB(); much less need to...

        'fraid you'll have to draw me a picture of that one :)

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