segmentation fault in event-driven library wrapped with swig

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segmentation fault in event-driven library wrapped with swig

by Sri-26 :: Rate this Message:

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Hello SWIG, perl experts:

With good help from swig-users posts & Stephen Chan in particular, I've figured out how to wrap a C event-driven library with SWIG. SWIG is really nice tool! I'm able to call APIs and register perl-sub as callback into the C library. If I invoke the perl callback as part of an API invoked from Perl script, the callback is called (in perls main thread). However, when the same callback handler invokes the callback via a different thread (based on async event), it crashes at the "dSP;" line.

I've tried adding "dTX" before "dSP;" and also tried enabling more macros to match how my perl is built. So far no luck. The line that crashes is below (pre-processor output). "dTHX done" is printed, but crashes before "DSP done" is printed.

printf("entering perl callback handler...\n");
register PerlInterpreter *my_perl __attribute__((unused)) = ((PerlInterpreter *)pthread_getspecific((*Perl_Gthr_key_ptr(((void *)0)))));
printf("dTHX done...\n");
register SV **sp = (*Perl_Tstack_sp_ptr(((PerlInterpreter *)pthread_getspecific((*Perl_Gthr_key_ptr(((void *)0))))))); <-- CRASHES!!
printf("DSP done...\n");

The perl-callback handler code
------------------------------

void SWIG_Wrap_bsa_disc_callback(int event, tMy_MSG *p_data)
{
printf("entering perl callback handler...\n");
dTHX;
printf("dTHX done...\n");
dSP;
printf("DSP done...\n");
SV * sv = bsa_perl_disc_callback;
if (sv == (SV*)NULL)
croak("Internal error...\n");

printf("Preparing to call perl callback...\n");
PUSHMARK(SP);
XPUSHs(sv_2mortal(newSViv(event)));
printf("newSViv of %d done...\n", event);
XPUSHs(SWIG_NewPointerObj(SWIG_as_voidptr(p_data), SWIGTYPE_p_tMy_MSG, SWIG_SHADOW));
/* XPUSHs(sv_2mortal(newSVsv((SV *)p_data))); */
printf("newSVsv...\n");
PUTBACK;

printf("calling the Perl sub...\n");
/* Call the Perl sub */
call_sv(sv, G_DISCARD);
printf("Perl sub completed successfully...\n");
}

Options when running SWIG:
--------------------------

swig -includeall -I. -I <lots of others proj specific dirs> -perl5 -outdir <outdir> -module <module> my_api.i

Options when compliling _wrap.c:
--------------------------------

gcc -E -Dbool=char -fpic -D_REENTRANT -D_GNU_SOURCE -DTHREADS_HAVE_PIDS -DDEBIAN -fno-strict-aliasing -pipe -isystem /usr/local/include -D_LARGEFILE_SOURCE -D_FILE_OFFSET_BITS=64 -DSWIG -g -DMULTIPLICITY -DPERL_IMPLICIT_CONTEXT -DTHREADS_HAVE_PIDS -DUSE_LARGE_FILES -DUSE_PERLIO -DUSE_REENTRANT_API -DBSA_CLIENT -I/usr/lib/perl/5.8/CORE/

Output from perl -V
-------------------

Summary of my perl5 (revision 5 version 8 subversion 8) configuration:
Platform:
osname=linux, osvers=2.6.24-19-server, archname=i486-linux-gnu-thread-multi
uname='linux palmer 2.6.24-19-server #1 smp sat jul 12 00:40:01 utc 2008 i686 gnulinux '
config_args='-Dusethreads -Duselargefiles -Dccflags=-DDEBIAN -Dcccdlflags=-fPIC -Darchname=i486-linux-gnu -Dprefix=/usr -Dprivlib=/usr/share/perl/5.8 -Darchlib=/usr/lib/perl/5.8 -Dvendorprefix=/usr -Dvendorlib=/usr/share/perl5 -Dvendorarch=/usr/lib/perl5 -Dsiteprefix=/usr/local -Dsitelib=/usr/local/share/perl/5.8.8 -Dsitearch=/usr/local/lib/perl/5.8.8 -Dman1dir=/usr/share/man/man1 -Dman3dir=/usr/share/man/man3 -Dsiteman1dir=/usr/local/man/man1 -Dsiteman3dir=/usr/local/man/man3 -Dman1ext=1 -Dman3ext=3perl -Dpager=/usr/bin/sensible-pager -Uafs -Ud_csh -Ud_ualarm -Uusesfio -Uusenm -Duseshrplib -Dlibperl=libperl.so.5.8.8 -Dd_dosuid -des'
hint=recommended, useposix=true, d_sigaction=define
usethreads=define use5005threads=undef useithreads=define usemultiplicity=define
useperlio=define d_sfio=undef uselargefiles=define usesocks=undef
use64bitint=undef use64bitall=undef uselongdouble=undef
usemymalloc=n, bincompat5005=undef
Compiler:
cc='cc', ccflags ='-D_REENTRANT -D_GNU_SOURCE -DTHREADS_HAVE_PIDS -DDEBIAN -fno-strict-aliasing -pipe -I/usr/local/include -D_LARGEFILE_SOURCE -D_FILE_OFFSET_BITS=64',
optimize='-O2',
cppflags='-D_REENTRANT -D_GNU_SOURCE -DTHREADS_HAVE_PIDS -DDEBIAN -fno-strict-aliasing -pipe -I/usr/local/include'
ccversion='', gccversion='4.2.3 (Ubuntu 4.2.3-2ubuntu7)', gccosandvers=''
intsize=4, longsize=4, ptrsize=4, doublesize=8, byteorder=1234
d_longlong=define, longlongsize=8, d_longdbl=define, longdblsize=12
ivtype='long', ivsize=4, nvtype='double', nvsize=8, Off_t='off_t', lseeksize=8
alignbytes=4, prototype=define
Linker and Libraries:
ld='cc', ldflags =' -L/usr/local/lib'
libpth=/usr/local/lib /lib /usr/lib
libs=-lgdbm -lgdbm_compat -ldb -ldl -lm -lpthread -lc -lcrypt
perllibs=-ldl -lm -lpthread -lc -lcrypt
libc=/lib/libc-2.7.so, so=so, useshrplib=true, libperl=libperl.so.5.8.8
gnulibc_version='2.7'
Dynamic Linking:
dlsrc=dl_dlopen.xs, dlext=so, d_dlsymun=undef, ccdlflags='-Wl,-E'
cccdlflags='-fPIC', lddlflags='-shared -L/usr/local/lib'

Characteristics of this binary (from libperl):
Compile-time options: MULTIPLICITY PERL_IMPLICIT_CONTEXT
PERL_MALLOC_WRAP THREADS_HAVE_PIDS USE_ITHREADS
USE_LARGE_FILES USE_PERLIO USE_REENTRANT_API
Built under linux
Compiled at Jan 14 2009 22:34:36
@INC:
/etc/perl
/usr/local/lib/perl/5.8.8
/usr/local/share/perl/5.8.8
/usr/lib/perl5
/usr/share/perl5
/usr/lib/perl/5.8
/usr/share/perl/5.8
/usr/local/lib/site_perl
.

output from gcc -v
------------------

gcc -v
Using built-in specs.
Target: i486-linux-gnu
Configured with: ../src/configure -v --enable-languages=c,c++,fortran,objc,obj-c++,treelang --prefix=/usr --enable-shared --with-system-zlib --libexecdir=/usr/lib --without-included-gettext --enable-threads=posix --enable-nls --with-gxx-include-dir=/usr/include/c++/4.2 --program-suffix=-4.2 --enable-clocale=gnu --enable-libstdcxx-debug --enable-objc-gc --enable-mpfr --enable-targets=all --enable-checking=release --build=i486-linux-gnu --host=i486-linux-gnu --target=i486-linux-gnu
Thread model: posix
gcc version 4.2.4 (Ubuntu 4.2.4-1ubuntu4)

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