in reply to Extending & Embedding Perl simultaneously: How to share a scalar between perl callback sub and main body?

Works for me (ActiveState Perl 10.1 on Windoze).

Did you miss the syntax error in your code (missing ; after until)? Try use warnings;

Here is my C:
#include "EXTERN.h"
#include "perl.h"
#include "XSUB.h"

#include "ppport.h"

#include "const-c.inc"

MODULE = MyModule        PACKAGE = MyModule        

INCLUDE: const-xs.inc

int
RegisterCB (SV *SubRef)

    CODE:
    
    ENTER;
    SAVETMPS;
    PUSHMARK(SP);
    
    XPUSHs(sv_2mortal(newSVpv("Some event",0)));
    XPUSHs(sv_2mortal(newSVpv("Some pdata",0)));
    
    PUTBACK;
    call_sv(SubRef, G_DISCARD);
    
    FREETMPS;
    LEAVE;
    
    RETVAL = 1;
    OUTPUT:
        RETVAL

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Here is the Perl (its a long time since I didn't use strict;):
use MyModule;
use warnings;

#shared scalar
$cb_done = 0;

#This cb would be invoked by the cloned interpreter in the
#C library.  This works fine.
sub cb_one
{
  ($event, $pdata) = @_;
  #This line is printed.
  print "event : ", $event, "\n";
  $cb_done = 1;
}

$status = MyModule::RegisterCB(\&main::cb_one);

do
{
   sleep (5);
} until ($cb_done == 1);

#This line is printed as $cb_done becomes 1 
#in the main of the perl script
print "CB was invoked : $cb_done\n";

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and here is the output:
C:\gash\MyModule>test.pl
Name "main::pdata" used only once: possible typo at C:\gash\MyModule\t
+est.pl line 11.
Name "main::status" used only once: possible typo at C:\gash\MyModule\
+test.pl line 17.
event : Some event
CB was invoked : 1

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Update: original code was not passing parameters to the callback.
Update 2: I hadn't freed the temporaries and closed the scope
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Re^2: Extending & Embedding Perl simultaneously: How to share a scalar between perl callback sub and main body?
by almut (Canon) on Dec 01, 2009 at 14:26 UTC

    My guess would be the problem is that the OP is using perl_clone() (which you are not), and that the callback code is being executed in the wrong (cloned) interpreter.   (As usual, it would help to see the OP's actual code, though...)

[reply]
[d/l]
      Thanks for all the comments!

      Apologies for typo in the code sample. I tried prefixing "our", but that didnt change the result.

      As almut said, I am using a cloned interpreter and the perl sub/callback is executed in the cloned interpreter context. So, is the problem in how I'm cloning it? Or does cloning by definition mean, I cannot "share". Here is a post describing how I've done the embedding.

      One "crude" way I can think of is to implement a "shared memory" API on C side to save/retrieve data between the subs and main. Perhaps CPAN has modules like this already..but I'm really hoping there is a more "natural" solution.

      http://markmail.org/thread/cjbhybjfikuirvud

      http://markmail.org/thread/inetppjegt5iecl5

[reply]
        Hi All,

        Hoping to get some pointers as I am really stuck here. I couldnt yet figure out the cause of the problem.

        I also couldnt find any package in CPAN to "hack" around this issue : most sharing related packages seem really geared toward multi-process, distributed sharing or persistance. None that are simple/for my case. I guess I've to write my own workaround? :(

        Thx

        ps: I'm in Asian timezone, hence the "delays" in responding back to posts.

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