This reminds me of similar struggles that I had about a year ago. I posted a question about my situation (How to use Win32::API to access variable in DLL file?) and got very useful help from BrowserUk about how accomplish what I wanted using just the Win32 module. You might want to check it out to see if the information there might help you get started.

Of course, that was dealing with variables. For functions, you would use Win32::API. The combination of the post linked above and some sample code below might help get you going in the right direction.

use strict;

use Win32::API;

# Load the DLL
my $dll = Win32::LoadLibrary('CrappyLibrary.dll') || die $^E;

# Import the function
my $func = new Win32::API('CrappyLibrary.dll','RegisterClient2','PP','
+I');
if (not defined $func) {die "Unable to import 'RegisterClient2' functi
+on.\n";}

my $client_id = 1;
my $ip_addr = "192.168.1.1";

# Call the function
my $value = $func->Call($client_id,$ip_addr);

# unload DLL
Win32::FreeLibrary($dll);
[download]

Hope this helps!

If I try it with this syntax ('PP', 'I'), the perl interpreter crashes (I get that lovely "The program Perl Command Line Interpreter encountered an error and needs to close" dialog box.)

it gave me an error message: Can't call method "Call" on an undefined value at (eval 4) line 2.

From the error message, it seems likely that it either: failed to load the dll; or locate the function. If you added an error check, it might tell you which, and why. Eg:

Win32::API->Import(
    $S{DLL_path}, 
    'int RegisterClient2(int *pnClientId, char *pszIPAddress)'
) or die $^E;
[download]

use Inline C => Config => MYEXTLIB => 'd:\path\to\CrappyLibrary.dll',

That should point to the CrappyLibrary.lib, not the .dll. You do have the .lib file?

Do you have the utility: dumpbin.exe on your system?

As for the Win32::API method, I think it finds both the dll and the function in it. If it failed at either task, it would croak something like "Undefined sub &main::RegisterClient2 in..." - which it did, when I misspelled the path. I'll try to check $^E tomorrow, but the fact that the whole program crashed when I used the $function = Win32::API->new(), $function->Call() syntax doesn't fill me with too much hope.

As for the Inline method: no, no .lib, only the .dll. I've found some advice on the net that said MinGW is able to use the dll directly. However, there might be a path problem related to MinGW's setup (or whatever) here that I can't figure out.

I don't have dumpbin.exe, at least I'm not aware of it. (Can't tell now, as I'm writing from a different machine)

Given this C:

#include <stdio.h>

__declspec(dllexport) int
RegisterClient2(int *pnClientId, const char *pszIPAddress) {
    printf( "id:%d  addr: %s\n", *pnClientId, pszIPAddress );
    return 12345;
}
[download]

Compiled to a DLL like this:

C:\test>cl /LD /MT 853196dll.c
Microsoft (R) C/C++ Optimizing Compiler Version 15.00.21022.08 for x64
Copyright (C) Microsoft Corporation.  All rights reserved.

853196dll.c
Microsoft (R) Incremental Linker Version 9.00.21022.08
Copyright (C) Microsoft Corporation.  All rights reserved.

/out:853196dll.dll
/dll
/implib:853196dll.lib
853196dll.obj
   Creating library 853196dll.lib and object 853196dll.exp
[download]

And this Inline::C:

#! perl -slw
use strict;
use Inline C => Config => BUILD_NOISY => 1, LIBS => 'c:\test\853196dll
+.lib';
use Inline C => <<'END_C',  NAME => '_853198_IC', CLEAN_AFTER_BUILD =>
+ 0;

int RegClient( SV *id, SV *IP ) {
    int c_id = SvIV( id );
    char *c_ip = SvPVX( IP );
    return RegisterClient2( &c_id, c_ip );
}

END_C

print RegClient( 123, 'fred' );
[download]

Running the Perl code gives:

C:\test>853196-ic.pl
Starting Build Preprocess Stage
Finished Build Preprocess Stage

Starting Build Parse Stage
Finished Build Parse Stage

Starting Build Glue 1 Stage
Finished Build Glue 1 Stage

Starting Build Glue 2 Stage
Finished Build Glue 2 Stage

Starting Build Glue 3 Stage
Finished Build Glue 3 Stage

Starting Build Compile Stage
  Starting "perl Makefile.PL" Stage
Writing Makefile for _853198_IC
  Finished "perl Makefile.PL" Stage

  Starting "make" Stage

Microsoft (R) Program Maintenance Utility Version 9.00.21022.08
Copyright (C) Microsoft Corporation.  All rights reserved.

        C:\Perl64\bin\perl.exe C:\Perl64\lib\ExtUtils\xsubpp  -typem
        cl -c  -IC:/test  -nologo -GF -W3 -MD -Zi -DNDEBUG -Ox -GL 
_853198_IC.c
_853198_IC.xs(7) : warning C4244: 'initializing' : conversion from '
_853198_IC.xs(9) : warning C4013: 'RegisterClient2' undefined; assum
Running Mkbootstrap for _853198_IC ()
        C:\Perl64\bin\perl.exe -MExtUtils::Command -e "chmod" -- 644
        C:\Perl64\bin\perl.exe -MExtUtils::Mksymlists  -e "Mksymlists
        link -out:blib\arch\auto\_853198_IC\_853198_IC.dll -dll -nolo
2.lib" "C:\Program Files\Microsoft SDKs\Windows\v6.1\Lib\X64\winspool
rosoft SDKs\Windows\v6.1\Lib\X64\uuid.lib" "C:\Program Files\Microsof
\Microsoft Visual Studio 9.0\VC\Lib\amd64\msvcrt.lib" -def:_853198_IC
   Creating library blib\arch\auto\_853198_IC\_853198_IC.lib and obje
Generating code
Finished generating code
        if exist blib\arch\auto\_853198_IC\_853198_IC.dll.manifest mt
        if exist blib\arch\auto\_853198_IC\_853198_IC.dll.manifest de
        C:\Perl64\bin\perl.exe -MExtUtils::Command -e "chmod" -- 755
        C:\Perl64\bin\perl.exe -MExtUtils::Command -e "cp" -- _85319
        C:\Perl64\bin\perl.exe -MExtUtils::Command -e "chmod" -- 644 
  Finished "make" Stage

  Starting "make install" Stage

Microsoft (R) Program Maintenance Utility Version 9.00.21022.08
Copyright (C) Microsoft Corporation.  All rights reserved.

Files found in blib\arch: installing files in blib\lib into architectu
+re 
Installing C:\test\_Inline\lib\auto\_853198_IC\_853198_IC.dll
Installing C:\test\_Inline\lib\auto\_853198_IC\_853198_IC.exp
Installing C:\test\_Inline\lib\auto\_853198_IC\_853198_IC.lib
Installing C:\test\_Inline\lib\auto\_853198_IC\_853198_IC.pdb
  Finished "make install" Stage

  Starting Cleaning Up Stage
  Finished Cleaning Up Stage

Finished Build Compile Stage

id:123  addr: fred
12345
[download]

Whether you can adapt that to work with MinGW, and no .lib I don't know.

---

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.

RIP an inspiration; A true Folk's Guy

Do you at least know what calling convention the DLL was built with?

use strict;
use warnings;
use Inline C => Config =>
MYEXTLIB  => 'd:\path\to\CrappyLibrary.dll',
INC => '-Id:\path\to',
BUILD_NOISY => 1;

use Inline C => 'DATA';

my $result = RegisterClient2($client_id, $S{read_IP});

__DATA__
__C__
#include "Easy4ApiDef.h"
[download]

use strict;
use warnings;
use Inline C => Config =>
MYEXTLIB  => 'd:\path\to\CrappyLibrary.dll',
INC => '-Id:\path\to',
BUILD_NOISY => 1;

use Inline C => 'DATA';

my $client_id = 5; #numeric
my $read_IP = 'whatever'; #string
my $result = wrap_RegisterClient2($client_id, $S{read_IP});

__DATA__
__C__
#include "Easy4ApiDef.h"

int wrap_RegisterClient2(int cl_id, char* read_ip) {
  return RegisterClient2(cl_id, read_ip);
}
[download]

Thanks to the help from BrowserUK, I've already figured out that I have to write wrapper functions.

I've tried it the way you did above:



int wrap_RegisterClient2(int cl_id, char* read_ip) {
  return RegisterClient2(cl_id, read_ip);
}
[download]


but it doesn't work, I get the same error message as in the case without the wrapper.

It works with BrowserUK's method. In fact, I have to go one step further:



int wRegisterClient2( SV *id, SV *IP ) {
    int c_id = SvIV( id );
    char *c_ip = SvPVX( IP );
    int result = RegisterClient2( &c_id, c_ip );
    printf("%d", c_id);
    sv_setiv(id, (IV) c_id);
    return result;
}
[download]


Basically, the purpose of this RegisterClient2 function is to establish contact with the instrument that listens on the given IP address, and it gives back a unique numeric id in nClientId that I have to use in further calls. And if I want to access this id from Perl, I have to write back the integer value into the SV that was passed to the wrapper.

So what follows now is me rolling up my sleeves and go elbow-deep into perlguts.

Thanks to the advice anyway.

I've tried it the way you did above:

int wrap_RegisterClient2(int cl_id, char* read_ip) {
  return RegisterClient2(cl_id, read_ip);
}
[download]

but it doesn't work, I get the same error message as in the case without the wrapper.

The problem, I believe, is that unless all the parameters, and the return type, are types that the default typemap knows how to handle, Inline::C doesn't wrap and export it. And it appears that the default typemap doesn't know how to handle int *.

So, whilst this works fine:

#! perl -slw
use strict;
#use Inline C => Config => BUILD_NOISY => 1;
use Inline C => <<'END_C',  NAME => '_test', CLEAN_AFTER_BUILD => 0;

int test( int i ) {
    return i;
}

END_C

print test( 123 );
__END__
C:\test>test
123
[download]

This doesn't:

#! perl -slw
use strict;
#use Inline C => Config => BUILD_NOISY => 1;
use Inline C => <<'END_C',  NAME => '_test', CLEAN_AFTER_BUILD => 0;

int test( int *i ) {
    return *i;
}

END_C

print test( 123 );

__END__
C:\test>test
Warning. No Inline C functions bound to Perl in C:\test\test.pl
Check your C function definition(s) for Inline compatibility

Use of inherited AUTOLOAD for non-method main::test() is deprecated at
+ C:\test\test.pl line 12.
Can't locate auto/main/test.al in @INC (@INC contains: C:\test\_Inline
+\lib C:/Perl64/site/lib C:/Perl64/lib .) at C:\test\test.pl line 12
[download]

There is the TYPEMAPS configuration option, but I haven't seen any (good) documentation on that. And finding the default typemap and looking at that doesn't yield many clues.

---

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.

RIP an inspiration; A true Folk's Guy

I've already figured out that I have to write wrapper functions.

Yes, the reference (in the update) to "yesterday's news" was meant to be acknowlegement of the fact that the isssue had already been resolved :-)

Cheers,
Rob

If int* doesn't work, I would use the following. It's basically the same as what you ended up doing using Inline::C, but in Pure Perl.

use Win32::API qw( );

my $register_client2 = Win32::API->new(
   $S{DLL_path}, 'RegisterClient2', 'PP', 'I',
);

sub register_client2 {
   my $ip = $_[1];
   my $id = pack('l', 0);  # Allocate space
   my $rv = $register_client2->Call($id, $ip);
   $_[0] = unpack('l', $id);
   return $rv;
}

register_client2(my $id, $ip)
   or die;
[download]

If the return value is just a boolean, you could do something more perlish.

sub register_client2 {
   my ($ip) = @_;
   my $id = pack('l', 0);  # Allocate space
   $register_client2->Call($id, $ip)
      or return ();
   return unpack('l', $id);
}

my ($id) = register_client2($ip)
   or die;
[download]

Note: psz would indicate char** rather than char*. That's confusing.

It turns out that my entire trip to Inline-land was useless¹, because Win32::SerialPort doesn't work for some reason if I use it.

However, I tried Win32::API again as a last resort, and it turned out that it works (and it doesn't crash) if and only if I import the functions like this:



my $RegisterClient2 = Win32::API->new($DLL, 'RegisterClient2', 'PP', '
+I', '_cdecl');
[download]


So my DLL was compiled with the _cdecl convention, and that's why it failed earlier.


---

1) not entirely useless, because I used to think that I can't use Inline on Windows at all. Now that I saw that it works, I have plans to rewrite some of the speed-critical parts of my earlier applications.

2) I agree that the DLL writer's version of Hungarian notation is confusing, but I can't do anything about it. I decided to go with it to stay in sync with the docs.