sunnyagarwal008 has asked for the wisdom of the Perl Monks concerning the following question:

Hi, As I said, its just a wrapper over C functions, there's not much of code in it (works with Dynaloader and AutoLoader). It works fine if I use this module alone. Here is the code: 
package ABC;

$ABC::VERSION = '0.02';

use strict;
use vars qw($VERSION @ISA @EXPORT @EXPORT_OK);

require Exporter;
require DynaLoader;
require AutoLoader;

@ISA = qw(Exporter AutoLoader DynaLoader);

# Items to export into callers namespace by default.
@EXPORT = qw(
         new_time_var
         dl_ascii_to_date
         dl_ascii_to_time
         dl_close_cache
);
@EXPORT_OK = qw();

bootstrap ABC $VERSION;

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and here is the wrapper module: 
package PQR;
use strict;
use vars qw($VERSION @ISA @EXPORT @EXPORT_OK);

require Exporter;
require AutoLoader;
use ABC;

$PQR::VERSION = $ABC::VERSION;

@ISA = qw(Exporter AutoLoader);
@EXPORT = qw(
         new_time_var
         dl_ascii_to_date
         dl_ascii_to_time
         dl_close_cache
            );
            
@EXPORT_OK = qw();

sub new_time_var
{
    return ABC::new_time_var(@_);
}

sub dl_ascii_to_date
{
    return ABC::dl_ascii_to_date(@_);
}

sub dl_ascii_to_time
{
    return ABC::dl_ascii_to_time(@_);
}

sub dl_close_cache
{
    return ABC::dl_close_cache(@_);    
}

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The actual subroutine signatures are: 
<new_time_var>()
<dl_ascii_to_date>(<string>)
<dl_ascii_to_time>(<string>, <dtp>)
<dl_close_cache>(<dcp>)

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When I test this using a script I get the following errors: 
>/u/agarwsun/test> perl -wc test.pl

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Prototype mismatch: sub PQR::new_time_var () vs none at /u/agarwsun/projects/packages/datelib/lib/perl5/5.8.6/i86pc-solaris/PQR.pm line 71.
Subroutine new_time_var redefined at /u/agarwsun/projects/packages/datelib/lib/perl5/5.8.6/i86pc-solaris/PQR.pm line 67.
Prototype mismatch: sub PQR::dl_ascii_to_date ($) vs none at /u/agarwsun/projects/packages/datelib/lib/perl5/5.8.6/i86pc-solaris/PQR.pm line 76. Subroutine dl_ascii_to_date redefined at /u/agarwsun/projects/packages/datelib/lib/perl5/5.8.6/i86pc-solaris/PQR.pm line 74.
Prototype mismatch: sub PQR::dl_ascii_to_time ($$) vs none at /u/agarwsun/projects/packages/datelib/lib/perl5/5.8.6/i86pc-solaris/PQR.pm line 81.
If I do not re-export the functions in PQR, and extend from ABC, I don't get the errors related to redefining subroutines, but I still get prototype mismatch errors:
Prototype mismatch: sub ABC::new_time_var () vs none at /u/agarwsun/projects/packages/datelib/lib/perl5/5.8.6/i86pc-solaris/PQR.pm line 22.
Prototype mismatch: sub ABC::dl_ascii_to_date ($) vs none at /u/agarwsun/projects/packages/datelib/lib/perl5/5.8.6/i86pc-solaris/PQR.pm line 27.
Prototype mismatch: sub Deshaw::DateLib::dl_ascii_to_time ($$) vs none at /u/agarwsun/projects/packages/datelib/lib/perl5/5.8.6/i86pc-solaris/PQR.pm line 32.

Replies are listed 'Best First'.
Re: Creating wrapper over a wrapper (prototype mismatch)
by moritz (Cardinal) on May 05, 2010 at 10:17 UTC
    What's the prototype of wrapper::ABC?

    You can disable prototype checking by adding a & in front wrapper::ABC(@_) but that might not always do you (or the original author of wrapper::ABC) wanted.

    Perl 6 - links to (nearly) everything that is Perl 6.
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Re: Creating wrapper over a wrapper
by Anonymous Monk on May 05, 2010 at 10:19 UTC
    That is very poor interface design which you should accomplish using variants of Exporter.

    i get errors saying that there is a prototype mismatch between the ABC here and wrapper::ABC. Can

    You should always copy/paste error message, and post code that reproduces the error (see How (Not) To Ask A Question for more)

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      Sorry, i replaced the actual question.
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Re: Creating wrapper over a wrapper
by almut (Canon) on May 05, 2010 at 14:09 UTC

    Try 

    use ABC ();

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    i.e., don't import the original functions into your PQR namespace, if you're going to define wrapper functions of the same name.

    (When writing just "use ABC;" the functions are automatically imported because they are in the @EXPORT array (as opposed to @EXPORT_OK) — see Exporter.)

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      use ABC ();

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      This also doesn't work. I still get errors.
      Too many arguments for ABC::new_time_var at /u/agarwsun/projects/packages/datelib/lib/perl5/5.8.6/i86pc-solaris/ABC.pm line 71, near "@_)"

      Not enough arguments for ABC::dl_ascii_to_time at /u/agarwsun/projects/packages/datelib/lib/perl5/5.8.6/i86pc-solaris/Deshaw/ABC.pm line 81, near "@_)"

      Not enough arguments for ABC::dl_compare at /u/agarwsun/projects/packages/datelib/lib/perl5/5.8.6/i86pc-solaris/Deshaw/ABC.pm line 91, near "@_)"

      The actual signatures of these subroutines are: 
      <new_time_var>() 
<dl_ascii_to_date>(<string>) 
<dl_ascii_to_time>(<string>, <dtp>)

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        Well, if the ABC::new_time_var function is declared with a prototype of (), meaning no arguments, you cannot call it with arguments in your wrapper, like ABC::new_time_var(@_).  Similarly for the other two functions.

        See also other threads on using prototypes here, to better understand how prototypes work in Perl (hint: they don't act like in C).

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