I am currently working on updating the SDL bindings for Perl. I need to do some callbacks for functions that need function pointers as parameters. Some functions do not need threaded callbacks and I have been able to get these to work. SDL_EventFilter implementation . 
/* Static Memory for event filter call back */
static SV * eventfiltersv;

int eventfilter_cb( const void * event)
{

    dSP;
    int count;
    int filter_signal;
    SV * eventref = newSV( sizeof(SDL_Event *) );
    void * copyEvent = safemalloc( sizeof(SDL_Event) );
    memcpy( copyEvent, event, sizeof(SDL_Event) );
    ENTER;
    SAVETMPS;
    PUSHMARK(SP);
    
    XPUSHs( sv_setref_pv( eventref, "SDL::Event", (void *)copyEvent) )
+;
    PUTBACK;
    
    count = call_sv(eventfiltersv, G_SCALAR);

    SPAGAIN;

    if (count != 1 ) croak("callback returned more than 1 value\n");  
+  

    filter_signal = POPi;

    FREETMPS;
    LEAVE;

    return filter_signal;
}

void
events_set_event_filter(callback)
    SV* callback
    CODE:
    eventfiltersv = callback;
    
    SDL_SetEventFilter( (SDL_EventFilter *)eventfilter_cb);

[download]
However this same method falls apart for functions which may be threaded. The Threaded callbacks are used in time_set_timer and time_add_timer. This is what I have tried 
#ifndef aTHX_
#define aTHX_
#endif


#ifdef USE_THREADS
#define HAVE_TLS_CONTEXT
#endif

/* For windows  */
#ifndef SDL_PERL_DEFINES_H
#define SDL_PERL_DEFINES_H

#ifdef HAVE_TLS_CONTEXT
PerlInterpreter *parent_perl = NULL;
extern PerlInterpreter *parent_perl;
#define GET_TLS_CONTEXT parent_perl =  PERL_GET_CONTEXT;
#define ENTER_TLS_CONTEXT \
        PerlInterpreter *current_perl = PERL_GET_CONTEXT; \
            PERL_SET_CONTEXT(parent_perl); { \
                            PerlInterpreter *my_perl = parent_perl;
#define LEAVE_TLS_CONTEXT \
                            } PERL_SET_CONTEXT(current_perl);
#else
#define GET_TLS_CONTEXT         /* TLS context not enabled */
#define ENTER_TLS_CONTEXT       /* TLS context not enabled */
#define LEAVE_TLS_CONTEXT       /* TLS context not enabled */
#endif

#endif



#include <SDL.h>

SV* set_timersv;


Uint32 set_timer_cb( Uint32 interval)
{
    Uint32 retval;
    int back;
    SV* cmd;
    ENTER_TLS_CONTEXT
    dSP;

    cmd = (SV*)set_timersv;

    ENTER;
    SAVETMPS;
    PUSHMARK(SP);
    XPUSHs(sv_2mortal(newSViv(interval)));
    PUTBACK;

    if (0 != (back = call_sv(cmd,G_SCALAR))) {
        SPAGAIN;
        if (back != 1 ) Perl_croak (aTHX_ "Timer Callback failed!");
        retval = POPi;    
    } else {
        Perl_croak(aTHX_ "Timer Callback failed!");
    }

    FREETMPS;
    LEAVE;

    LEAVE_TLS_CONTEXT
    
    return retval;

}

int
time_set_timer ( interval, callback )
    Uint32 interval
    SV* callback
    CODE:
        set_timersv = callback;
        RETVAL = SDL_SetTimer(interval, set_timer_cb);
        
    OUTPUT:
        RETVAL

[download]
To build the new SDL Perl redesign code please refer to this link . My goal is to be able to do this 
use SDL;
use SDL::Time;

SDL::init(SDL_INIT_TIMER);
my $time = 0;
SDL::Timer::set_timer(100, sub { $time++; return $_[0]} );
print 'this will not print!'

[download]
Currently this will die silently even with valgrind.

In reply to Threaded Callbacks in XS by kthakore

Title:
Use:  <p> text here (a paragraph) </p>
and:  <code> code here </code>
to format your post, it's "PerlMonks-approved HTML":


  • Posts are HTML formatted. Put <p> </p> tags around your paragraphs. Put <code> </code> tags around your code and data!
  • Titles consisting of a single word are discouraged, and in most cases are disallowed outright.
  • Read Where should I post X? if you're not absolutely sure you're posting in the right place.
  • Please read these before you post! —
  • Posts may use any of the Perl Monks Approved HTML tags:
    a, abbr, b, big, blockquote, br, caption, center, col, colgroup, dd, del, details, div, dl, dt, em, font, h1, h2, h3, h4, h5, h6, hr, i, ins, li, ol, p, pre, readmore, small, span, spoiler, strike, strong, sub, summary, sup, table, tbody, td, tfoot, th, thead, tr, tt, u, ul, wbr
  • You may need to use entities for some characters, as follows. (Exception: Within code tags, you can put the characters literally.)
            For:     Use:
    & &amp;
    < &lt;
    > &gt;
    [ &#91;
    ] &#93;
  • Link using PerlMonks shortcuts! What shortcuts can I use for linking?
  • See Writeup Formatting Tips and other pages linked from there for more info.