Re: Calling External DLL functions in Perl using Inline


<ben.sommer@xxxxxxx> wrote

> Taking that DLL example from the Inline::C cookbook...
>
> http://search.cpan.org/~ingy/Inline-0.44/C/C-Cookbook.pod#Win32
>
> use Inline C => DATA =>
> LIBS => '-luser32';
>
> $text = "@ARGV" || 'Inline.pm works with MSWin32. Scary...';
>
> WinBox('Inline Text Box', $text);
>
> __END__
> __C__
>
> #include <windows.h>
>
> int WinBox(char* Caption, char* Text) {
> return MessageBoxA(0, Text, Caption, 0);
> }
>
>
> That config directive "LIBS => '-luser32'" looks pretty key right? It
> says 'go call "user32.dll", right? Wrong. It does nothing. Remove it
> and the code compiles and runs the same.

No - I think that LIBS directive is saying "link to libuser32.a" - which you
should find in Cygwin's gcc/lib folder.
I think that script builds ok when you remove the LIBS directive because
libuser32.a is linked to automatically. That automatic linking is built in
by the ExtUtils modules. To verify, insert the following at the top of the
script:

use Inline C => Config =>
BUILD_NOISY => 1;

Then make some change to the C code in that script (to force it to rebuild -
add or delete some white space is sufficient).

Then re-run the script. Somewhere in the output you should see 'libuser32.a'
mentioned (along with a heap of other libs).

> Its the windows.h include file
> that makes this example - and probably all Win32 dlls - work under
> cygwin, thanks to all the hand-rolled header files in
> /usr/include/w32api.

You'll possibly find you don't even have to specifically include windows.h
either. Your Inline::C code will automatically include 'perl.h' and that
might lead to the inclusion of 'windows.h'. On my perls that's the way it
is, anyway. 'perl.h' includes 'win32.h' which includes 'windows.h'. It might
be different under Cygwin.

> I'd love to hear from people using Inline::C under
> cygwin with gcc and a _custom_ DLL file.
> How do you manage to link it.

To link directly to a dll (which is possible with gcc, but not with
Microsoft compilers) you specify the 'MYEXTLIB' config directive - eg:

MYEXTLIB => "/full_path/to_dll/MyDLL.dll",

> How do are you able to include your own header files?

You just list them as you would in normal C code. You can use the 'INC'
config directive to specify the directory that they are in (if they're not
already in some standard location):

INC => "-I/full_path/to_folder/that_contains/my_includes",

> Please prove me
> wrong! I'd even listen to people having success with ActiveState perl
> and Visual Studio (ugh).

I use gcc (MinGW) most of the time - but that's using 'gcc' in a native
Win32 environment - not in a Cygwin environment. I also use MSVC++ 7.0
(.NET) which is a very good compiler - though, for me, a little cumbersome
to use. I prefer to use MinGW as I find I'm a lot more comfortable with it.
I would never use Cygwin - for various reasons (most of which don't apply to
everybody .... or do I mean "anybody" ? :-).

>Off to post to the cygwin list...
>

For Inline::C questions, the best forum is the Inline mailing list. (See
http://lists.perl.org/index.cgi :-)

Cheers,
Rob


.

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