Re: How to setup the DynaLoader in a dynamically loaded perl?

On second glance, you did not dlsym'ed boot_DynaLoader() that's why xs_init() had trouble.

This is a complete, compilable and runnable example:

/*
author: bliako
date:   05/05/2020
for:    https://perlmonks.org/?node_id=11116476

compile with:

$(perl -MConfig -e 'print $Config{cc}') a.c $(perl -MExtUtils::Embed -
+e ccopts -e ldopts) -o aaa -ldl

run with:

./aaa -e 'print "hello there, I am a tiny wee Perl!!\n"'

*/
#include <EXTERN.h>
#include <perl.h>
#include "XSUB.h"
#include <dlfcn.h>

// void boot_DynaLoader (pTHX_ CV* cv);
/* this declares a function pointer as opposed to an external function
+ above */
void (*boot_DynaLoader)(pTHX_ CV* cv);

void xs_init(pTHX) {
    static const char file[] = __FILE__;
    dXSUB_SYS;
    PERL_UNUSED_CONTEXT;
    newXS( "DynaLoader::boot_DynaLoader", boot_DynaLoader, file );
}

static PerlInterpreter *my_perl;
int main( int argc, char **argv, char **env ) {
    /* find path to shared library */
    /* open shared lib */
    void *handle = dlopen("/usr/lib64/libperl.so.5.28.2", RTLD_NOW);

    /* Get entry point for perl_alloc */
    void* (*perl_alloc)();
    perl_alloc = (void *(*)() )dlsym(handle, "perl_alloc");
        /* Get all the functions you will be using from the library, t
+his one is obvious */
    boot_DynaLoader = (void (*)(pTHX_ CV* cv) )dlsym(handle, "boot_Dyn
+aLoader");

    /* Call perl_alloc */
    my_perl = perl_alloc();

    /* and so on */
    perl_construct(my_perl);
    perl_parse( my_perl, xs_init, argc, argv, env );
    int result = perl_run(my_perl);
    perl_destruct(my_perl);
    perl_free(my_perl);
    PERL_SYS_TERM();
    return result;
}
[download]

Edit: added a typecast to boot_DynaLoader = (void (*)(pTHX_ CV* cv) )dlsym(handle, "boot_DynaLoader");

bw, bliako

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Re^2: How to setup the DynaLoader in a dynamically loaded perl? by sciurius (Beadle) on May 05, 2020 at 20:00 UTC
Thanks for your helpful suggestions. Your example compiles and runs, but: `$ ldd aaa linux-vdso.so.1 (0x00007ffd0e4c6000) libperl.so.5.30 => /lib64/libperl.so.5.30 (0x00007fe9264b5000) libpthread.so.0 => /lib64/libpthread.so.0 (0x00007fe926493000) libdl.so.2 => /lib64/libdl.so.2 (0x00007fe92648c000) libc.so.6 => /lib64/libc.so.6 (0x00007fe9262c3000) libm.so.6 => /lib64/libm.so.6 (0x00007fe92617d000) libcrypt.so.2 => /lib64/libcrypt.so.2 (0x00007fe926142000)` [download] So it is already linked to the perl shared library. If I remove -lperl from the link arguments I get: in function `xs_init': /home/jv/tmp/aaa.c:28: undefined reference to `PL_thr_key' /bin/ld: /home/jv/tmp/aaa.c:28: undefined reference to `pthread_getspe +cific' /bin/ld: /home/jv/tmp/aaa.c:28: undefined reference to `Perl_newXS' [download] EDIT: Managed to get it going by adding a Perl_newXS function as follows: `CV* Perl_newXS(pTHX_ const char name, XSUBADDR_t subaddr, const char +filename) { CV* (imp)(tTHX, const char, XSUBADDR_t, const char); imp = (CV ()(tTHX, const char, XSUBADDR_t, const char)) dlsym( h +andle, "Perl_newXS" ); return (imp)(my_perl, name, subaddr, filename); }` [download] The complete proof-of-concept program is now: #include <stdio.h> #include <stdlib.h> #include <dlfcn.h> #include <EXTERN.h> #include <perl.h> void handle; / for dl / static PerlInterpreter my_perl; void (boot_DynaLoader)(pTHX_ CV cv); CV* Perl_newXS(pTHX_ const char name, XSUBADDR_t subaddr, const char +filename) { CV* (imp)(tTHX, const char, XSUBADDR_t, const char); imp = (CV ()(tTHX, const char, XSUBADDR_t, const char)) dlsym( h +andle, "Perl_newXS" ); return (imp)(my_perl, name, subaddr, filename); } void xs_init(pTHX) { static const char file[] = __FILE__; dXSUB_SYS; PERL_UNUSED_CONTEXT; newXS( "DynaLoader::boot_DynaLoader", boot_DynaLoader, file ); } int main( int argc, char argv, char env ) { /* open shared lib / handle = dlopen("perl530.so", RTLD_LAZY); if ( !handle ) { fprintf( stderr, "%s\n", dlerror() ); exit(EXIT_FAILURE); } / Get entry point for perl_alloc / void (perl_alloc)(); perl_alloc = (void()()) dlsym(handle, "perl_alloc"); / Call perl_alloc / my_perl = (perl_alloc)(); /* perl_construct / void (perl_construct)(void); perl_construct = (void()(void)) dlsym(handle, "perl_construct"); (perl_construct)(my_perl); /* boot_DynaLoader / boot_DynaLoader = (void ()(pTHX_ CV* cv)) dlsym(handle, "boot_DynaL +oader"); /* perl_parse / void (perl_parse)(void, void, int, char, char); perl_parse = (void()(void, void, int, char, char)) dlsym(hand +le, "perl_parse"); (perl_parse)(my_perl, xs_init, argc, argv, env); /* perl_run / int (perl_run)(void); perl_run = (int()(void)) dlsym(handle, "perl_run"); int result = (perl_run)(my_perl); /* perl_destruct / void(perl_destruct)(void); perl_destruct = (void()(void)) dlsym(handle, "perl_destruct"); (perl_destruct)(my_perl); /* perl_free / void(perl_free)(void); perl_free = (void()(void)) dlsym(handle, "perl_free"); (perl_free)(my_perl); return result; } [download] Build with: `$(perl -MConfig -e 'print $Config{cc}') p.c $(perl -MExtUtils::Embed -e ccopts ) -o aaa -ldl -Wl,--rpath=.` Although it seems that dynamic loading is not yet functional... For example, this fails: `aaa -MFcntl=:flock -E "say 1+LOCK_NB" Undefined subroutine &Fcntl::LOCK_NB called at -e line 1.` [download]	[reply] [d/l] [select]
Re^3: How to setup the DynaLoader in a dynamically loaded perl? by bliako (Abbot) on May 05, 2020 at 21:06 UTC
As I said, you will need to `dlsym` anything that you may use later. However, when I did this: `CV* (Perl_newXS)(pTHX_ const char name, XSUBADDR_t subaddr, const ch +ar filename); .... Perl_newXS = (CV ()(pTHX_ const char name, XSUBADDR_t subaddr, cons +t char filename) )dlsym(handle, "Perl_newXS");` [download] I got `error: ‘Perl_newXS’ redeclared as different kind of symbol /usr/lib64/perl5/CORE/proto.h:2517:19: note: previous declaration of ‘ +Perl_newXS’ was here 2517 \| PERL_CALLCONV CV Perl_newXS(pTHX_ const char name, XSUBADDR_ +t subaddr, const char filename);` [download] So, that's a neat trick you have there! (though I would make `imp` static)	[reply] [d/l] [select]