http://www.perlmonks.org?node_id=1069902

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

i have .h and .cpp file:

say_hi.h:

   extern "C" {
      void say_hi();
   }

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say_hi.cpp:

   #include <cstdio>
   #include "say_hi.h"
   void say_hi(){
   printf("hello workd!\n");
   }

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then i compile this with

g++ -I. -fPIC -c *.cpp
g++ -shared *.o -I. -olibsay_hi.so

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then use perl Inline CPP to call it:

>perl -e 'use Inline CPP=>q{  \
 #include "say_hi.h" \
 void test(){return say_hi(); } \
 }, INC=>"-I.",LIBS=>"-lsay_hi"; test()'

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Here I got:

perl: symbol lookup error: /home/xxx/test_so/_Inline/lib/auto/e_8555/e_8555.so: undefined symbol: say_hi

But if I test the .so file with below .cpp file test.cpp:

#include "say_hi.h"
main() {
  say_hi();
}

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Compile it:

g++ -L. -lsay_hi test.cpp -o test

Run the test:

>test
hello workd!

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Is there something wrong with my Perl (v5.8.0), or did I miss anything?

thanks a lot!

Replies are listed 'Best First'.
Re: use Inline CPP to call function in so file not working
by syphilis (Archbishop) on Jan 09, 2014 at 06:04 UTC
    If you're wanting to link directly to 'libsay_hi.so', you might need to make use of the MYEXTLIB config option: 
    use Inline CPP => Config => MYEXTLIB => '/full/path_to/libsay_hi.so';

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    Cheers,
    Rob
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[d/l]

      If you're wanting to link directly to 'libsay_hi.so', you might need to make use of the MYEXTLIB config option:

      That seems to go over a lot smoother than using LIBS => "-l ..." option

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      This works! Many Thanks!
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Re: use Inline CPP to call function in so file not working
by davido (Cardinal) on Jan 09, 2014 at 04:18 UTC

    I think Anonymous Monk has provided enough for you to get things going.

    If there's something in the POD that needs clarification, with the hindsight of having resolved your issue, please let me know. If it's something that would also be applicable to Inline::C, let syphilis know. We try to keep the documentation as approachable as possible, though given the complexity involved, it's easy to fall short in that regard. ;)


    Dave

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[reply]
[d/l]
[select]
        So far I've tried all sugestions to solve my problem ...

        I've just done some checking with Inline::C (not Inline::CPP), and it seems that you should also be able to link directly to the .so file using 
        LIBS => '-L/path/to/so_file -lsay_hi',

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        If that works with Inline::C (which it seems to), the same thing should probably be working with Inline::CPP.
        Of course, if libsay_hi.so is already in a location where the linker will find it, then the "-L/path/to/so_file" part should not be necessary.

        Could you double-check using "LIBS" with Inline::CPP ?

        I was initially of the view that EU::MM might do things that prevented you from linking directly to a shared object using the "LIBS" option - and that MYEXTLIBS would then be the *only* way of achieving this.
        But, like I say, this now seems to me to *not* be the case - with Inline::C and perl-5.18.0 at least.

        Cheers,
        Rob
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[d/l]

        as I followed the instructions and examples there then end up with this question. I think other perl user will proberbly ask the same.

        While I believe adding examples is good, I doubt other perl users will probably ask the same, because 90% of the time you're connecting to an existing libfoobar.a you're not creating your own libfoobar.a (which is regular c/c++ programming)

        Answers from Anonymous Monk:

        You're confused by PerlMonks codewrapping feature, I never suggested -l+say_hi , I suggested you create a libsay_hi.a through whatever means, so that when you say -lsay_hi and g++/gcc/ld looks for libsay_hi.a it can find one

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Re: use Inline CPP to call function in so file not working
by Anonymous Monk on Jan 09, 2014 at 04:03 UTC

    Is there something wrong with my Perl (v5.8.0)

    Yes, many many things detailed in the various perldeltas

    or did I miss anything?

    Yes you did. When you say -lsay_hi this means look for libsay_hi.a which maybe links to libsay_hi.so , or maybe is a static library

    You're missing libsay_hi.a

    Another tip is use 

    use Cwd();
use Inline C => Config => BUILD_NOISY => 1, CLEAN_AFTER_BUILD => 0;
use Inline CPP => <<'END', NAME => 'doodle', INC => "-I.", LIBS => "-l
+say_hi";
#include "say_hi.h"
void test(){
    return say_hi();
} 

END
test();
__END__

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    and then examine doodle directory to work out whats what .
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[d/l]

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