Problem on XS module loading

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

Hi monks! I'm learning how to use XS. I want to have an C++ refcounted object that use an perl HV for ref-counting and custom data storage. However I got a weird error message while loading my module:

Can't load 'blib/arch/auto/xstest/xstest.so' for module xstest: blib/a
+rch/auto/xstest/xstest.so: undefined symbol: _ZN10Referenced15_perl_m
+g_vtableE at /usr/lib64/perl5/5.12.3/x86_64-linux/DynaLoader.pm line 
+200.
 at show.pl line 3
Compilation failed in require at show.pl line 3.
BEGIN failed--compilation aborted at show.pl line 3.
[download]

I'm using gentoo linux, gcc version 4.4.5, perl version 5.12

Comment on Problem on XS module loading Download Code

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Re: Problem on XS by BrowserUk (Patriarch) on Oct 28, 2011 at 03:53 UTC
You are suffering from the fact that XS was never designed to work with C++. C++ does Name Mangling. `_ZN10Referenced15_perl_mg_vtableE` is what the PerlAPI symbol `perl_mg_vtable` looks like after your C++ compiler has performed its mangling algorithm upon it. As PerlAPIs are built with C, which doesn't use (compatible) name-mangling, ne'er the twain shall meet. It is very difficult to try and "fix up" such mismatches because C++ name mangling is not standardised across different compilers. With the rise and rise of 'Social' network sites: 'Computers are making people easier to use everyday' Examine what is said, not who speaks -- Silence betokens consent -- Love the truth but pardon error. "Science is about questioning the status quo. Questioning authority". In the absence of evidence, opinion is indistinguishable from prejudice.	[reply] [d/l] [select]
Re^2: Problem on XS by llancet (Friar) on Oct 28, 2011 at 04:38 UTC
I guessed it might be caused by C++ issue. But in document perlxs, there is a chapter of "using XS with C++", so there may be some magics?	[reply]
Re^3: Problem on XS by BrowserUk (Patriarch) on Oct 28, 2011 at 04:56 UTC
so there may be some magics? Truthfully, I don't know. I know enough to diagnose the problem, but not enough to resolve it. From what I see in that section -- and the rest of the document -- there doesn't appear to be any mention of how to persuade the C++ compiler to not mangle the names of Perl's C APIs called from within the XS code. The normal way of doing this -- thereby allowing C apis to be called from C++ code -- is to use `extern "C"{}` as described here As far as I can tell that would require you to modify Perl's header files, which doesn't seem right. With the rise and rise of 'Social' network sites: 'Computers are making people easier to use everyday' Examine what is said, not who speaks -- Silence betokens consent -- Love the truth but pardon error. "Science is about questioning the status quo. Questioning authority". In the absence of evidence, opinion is indistinguishable from prejudice.	[reply] [d/l]
Re^3: Problem on XS by Anonymous Monk on Oct 28, 2011 at 07:33 UTC
so there may be some magics? IIRC, last time you asked about XS/C++ you got links to several working examples, which show `#ifdef __cplusplus extern "C" {` [download] So what do you have?	[reply] [d/l]
Re^4: Problem on XS by llancet (Friar) on Oct 28, 2011 at 08:18 UTC
Re^5: Problem on XS by Anonymous Monk on Oct 28, 2011 at 23:38 UTC
Some notes below your chosen depth have not been shown here
Re: Problem on XS by Anonymous Monk on Oct 28, 2011 at 03:52 UTC
Problem on XS <<<< effective node title goes here :) see How do I compose an effective node title? For example Can't load .so for module undefined symbol Using said title as search terms yields DBD::Oracle install fail, Re^2: Fuse and fuse_loop, Do XS-components require special considerations with CGI? [SOLVED], which deal with this topic and explain about ldd...	[reply]