lamchob has asked for the wisdom of the Perl Monks concerning the following question:

Intro

I'm trying to create a PerlXS-Modul, that uses a C++ Class. Before diving into the complex matter, I wanted to create a little Test, to see how the basics work, since this is my first time using PerlXS. Luckily I tumbled upon this http://www.perlmonks.org/?node_id=853194 thread, which is a pretty awesome piece of knowledge. So I started to create my own litte Testclass, according to the example in the tutorial.

The Problem

While 'make' works without errors, but the include ( make test etc.) of the modul into a perl script fails with the following error: 
Error:  Can't load '/home/dr/Abby/XS/Mytest/blib/arch/auto/Mytest/Myte
+st.so' for module Mytest: /home/dr/Abby/XS/Mytest/blib/arch/auto/Myte
+st/Mytest.so: undefined symbol: _ZN7MyClassD1Ev at /usr/lib/perl/5.14
+/DynaLoader.pm line 184.

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I tried to as close a possibly with the tutorial, but something is off, and I don't know what. Has anyone seen something similar? Any hints?

Code

I created the folder structure using h2xs -A -n Mytest In there I created a folder, called 'myclass', where the code for my C++ Class

C++ Part

myclass.h 
#ifndef MyClass_H
#define MyClass_H

class MyClass {
public:
    MyClass(int a, int b);
    ~MyClass();
    int area();
private:
    int length;
    int width;
};

#endif

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myclass.cpp 
#include "myclass.h"

using namespace std;

MyClass::MyClass (int length, int width) {
    this->length = length;
    this->width = width;
}

int MyClass::area() {
    return this->length*this->width;
}
</class>

Makefile.PL
This I basically took from the Tutorial mentioned in the Into, and adj
+usted it to my changes. 
<code>
use ExtUtils::MakeMaker;
my ( $CC, $Verbose ) = ( 'g++', 1 );
WriteMakefile(
    NAME    => 'Mytest::myclass',
    SKIP    => [qw(all static static_lib dynamic dynamic_lib)],
    clean   => {'FILES' => 'libmyclass$(LIB_EXT) unitTest'},
    CC      => $CC, # Our CPP compiler
    LD      => '$(CC)',
    CCFLAGS => '-fPIC', # this instructs the CPP compiler to use "Posi
+tion independence", basically a shared library, more details here
                            # http://www.fpx.de/fp/Software/tcl-c++/tc
++l-c++.html
);
sub MY::top_targets {
'
all :: static
pure_all :: static
static :: libmyclass$(LIB_EXT)

libmyclass$(LIB_EXT): $(O_FILES)
        $(AR) cr libmyclass$(LIB_EXT) $(O_FILES)
        $(RANLIB) libmyclass$(LIB_EXT)

bin: $(O_FILES)
        $(LD) $(O_FILES) -o unitTest
';
}

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To test all these I wrote a litte unitTest, which worked fine. So I can safely assume, that my problem is not within the C++ part.

XS-Part and Makefile.PL

Mytest.xs 
#include "EXTERN.h"
#include "perl.h"
#include "XSUB.h"

#include "ppport.h"
#include "myclass/myclass.h"


MODULE = Mytest        PACKAGE = Mytest        

MyClass*
MyClass::new(int a, int b)

int 
MyClass::area()

void 
MyClass::DESTROY()

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typemap  MyClass *      T_PTROBJ Makefile.PL 
use 5.014002;
use ExtUtils::MakeMaker;
# See lib/ExtUtils/MakeMaker.pm for details of how to influence
# the contents of the Makefile that is written.
my $CC = 'g++';

WriteMakefile(
    NAME              => 'Mytest',
    VERSION_FROM      => 'lib/Mytest.pm', # finds $VERSION
    PREREQ_PM         => {}, # e.g., Module::Name => 1.1
    CC                => $CC, # Our CPP compiler
    LD                => '$(CC)',
    ($] >= 5.005 ?     ## Add these new keywords supported since 5.005
      (ABSTRACT_FROM  => 'lib/Mytest.pm', # retrieve abstract from mod
+ule
       AUTHOR         => 'Dennis Rieber <dr@>') : ()),
    LIBS              => [''], # e.g., '-lm'
    DEFINE            => '', # e.g., '-DHAVE_SOMETHING'
    INC               => '-I.', # e.g., '-I. -I/usr/include/other'
  # Un-comment this if you add C files to link with later:
    # OBJECT            => '$(O_FILES)', # link all the C files too
    MYEXTLIB          => 'myclass/libmyclass$(LIB_EXT)',
#    TYPEMAPS          => ['perlobject.map' ],
);

sub MY::postamble {
'
$(MYEXTLIB): myclass/Makefile
    cd myclass && $(MAKE) $(PASSTHRU)
';
}

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t/Mytest.t 
# Before `make install' is performed this script should be runnable wi
+th
# `make test'. After `make install' it should work as `perl Mytest.t'

#########################

# change 'tests => 1' to 'tests => last_test_to_print';

use strict;
use warnings;

use Test::More tests => 2;
BEGIN { use_ok('Mytest') };

my $class = new Mytest::MyClass(2,3);
is($class->area(), 6, 'area_ok')

#########################

# Insert your test code below, the Test::More module is use()ed here s
+o read
# its man page ( perldoc Test::More ) for help writing this test scrip
+t.

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MANIFEST 
Changes
Makefile.PL
MANIFEST
Mytest2.xs
ppport.h
README
t/Mytest2.t
lib/Mytest2.pm

[download]
This should be all the relevant code, or did I miss something?

Replies are listed 'Best First'.
Re: Unable to use created PerlXS Modul ( using c++ )
by Anonymous Monk on Feb 10, 2014 at 09:46 UTC

    Did libmyclass build successfully? What files did you get? Do any of these files (or their folder paths) get mentioned in Makefile? You should try adding those LIBS=-Ldirpath

    Also, all the myclass files should be in MANIFEST also

[reply]
      libmyclass builds successfully, and the test I created for it works fine. I added the myclass/myclass.h/.cpp and the Makefile.PL to the manifest. Added '-L/home/dr/Abby/XS/Mytest/myclass' to LIBS. myclass/libmyclass gets mentions in the Makefile as MYEXTLIB. Nothing solved the problem so far. This is the output of the make-command: 
      Skip blib/lib/Mytest.pm (unchanged)
cd myclass && make 
make[1]: Betrete Verzeichnis '/home/dr/Abby/XS/Mytest/myclass'
g++ -c   -fPIC -O2 -g   -DVERSION=\"\" -DXS_VERSION=\"\" -fPIC "-I/usr
+/lib/perl/5.14/CORE"   myclass.cpp
ar cr libmyclass.a myclass.o unitTest.o
: libmyclass.a
make[1]: Verlasse Verzeichnis '/home/dr/Abby/XS/Mytest/myclass'
make[1]: Betrete Verzeichnis '/home/dr/Abby/XS/Mytest/myclass'
make[1]: Für das Ziel »all« ist nichts zu tun.
make[1]: Verlasse Verzeichnis '/home/dr/Abby/XS/Mytest/myclass'
g++ -c  -I. -D_REENTRANT -D_GNU_SOURCE -DDEBIAN -fno-strict-aliasing -
+pipe -fstack-protector -I/usr/local/include -D_LARGEFILE_SOURCE -D_FI
+LE_OFFSET_BITS=64 -O2 -g   -DVERSION=\"0.01\" -DXS_VERSION=\"0.01\" -
+fPIC "-I/usr/lib/perl/5.14/CORE"   Mytest.c
Running Mkbootstrap for Mytest ()
chmod 644 Mytest.bs
rm -f blib/arch/auto/Mytest/Mytest.so
g++  -shared -O2 -g -L/usr/local/lib -fstack-protector Mytest.o  -o bl
+ib/arch/auto/Mytest/Mytest.so myclass/libmyclass.a    \
             \
      
chmod 755 blib/arch/auto/Mytest/Mytest.so
cp Mytest.bs blib/arch/auto/Mytest/Mytest.bs
chmod 644 blib/arch/auto/Mytest/Mytest.bs
Manifying blib/man3/Mytest.3pm

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      and this for make test 
      make[1]: Betrete Verzeichnis '/home/dr/Abby/XS/Mytest/myclass'
make[1]: Für das Ziel »all« ist nichts zu tun.
make[1]: Verlasse Verzeichnis '/home/dr/Abby/XS/Mytest/myclass'
PERL_DL_NONLAZY=1 /usr/bin/perl "-MExtUtils::Command::MM" "-e" "test_h
+arness(0, 'blib/lib', 'blib/arch')" t/*.t
t/Mytest.t .. 1/2 
#   Failed test 'use Mytest;'
#   at t/Mytest.t line 12.
#     Tried to use 'Mytest'.
#     Error:  Can't load '/home/dr/Abby/XS/Mytest/blib/arch/auto/Mytes
+t/Mytest.so' for module Mytest: /home/dr/Abby/XS/Mytest/blib/arch/aut
+o/Mytest/Mytest.so: undefined symbol: _ZN7MyClassD1Ev at /usr/lib/per
+l/5.14/DynaLoader.pm line 184.
#  at (eval 4) line 2
# Compilation failed in require at (eval 4) line 2.
# BEGIN failed--compilation aborted at (eval 4) line 2.
Can't locate object method "new" via package "Mytest" at t/Mytest.t li
+ne 14.
# Looks like you planned 2 tests but ran 1.
# Looks like you failed 1 test of 1 run.
# Looks like your test exited with 255 just after 1.
t/Mytest.t .. Dubious, test returned 255 (wstat 65280, 0xff00)
Failed 2/2 subtests 

Test Summary Report
-------------------
t/Mytest.t (Wstat: 65280 Tests: 1 Failed: 1)
  Failed test:  1
  Non-zero exit status: 255
  Parse errors: Bad plan.  You planned 2 tests but ran 1.
Files=1, Tests=1,  0 wallclock secs ( 0.03 usr  0.00 sys +  0.03 cusr 
+ 0.00 csys =  0.06 CPU)
Result: FAIL
Failed 1/1 test programs. 1/1 subtests failed.
make: *** [test_dynamic] Fehler 255

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Re: Unable to use created PerlXS Modul ( using c++ )
by lamchob (Initiate) on Feb 11, 2014 at 09:57 UTC

    I've been tinkering a bit, and found the following baviour: When the Classfunctions of the c++ class are placed in the headerfile or the class is directly defined in the head of the .xs file like this:

     class foo {
public:
  foo(int a) {
    value = a;
  }
private:
  int value;
}

    [download]
    (like in http://www.johnkeiser.com/perl-xs-c%2B%2B.html another neat XS/C++ source), everything works as expected. The moment the class-definition is separated from the actual code, eg. having a .h and a .cpp file, the tests begin to fail. Additionally, reproducing EXMAPLE 4 of perlxstut (including a pure c lib with separate .h and .c files, no c++) works just fine.

    Conclusion:

    From what I see, the problem is somewhere located in the process where libmyclass.a is bound into Mytest.so, or in the creation of libmyclass.a itself.

    PS: This is my first time posting something on perlmonks, and writing about your problem really hepls to think about it.wow. Any maybe this thread will help another lost XS-Soul on their journey...feels good, man :D

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