I think the following would do:

my $CheckLen = Win32::API->new('...', 'CheckLen', 'P', 'V')
    or die ...;

sub CheckLen {
    $len = pack('L', $_[0]);
    $CheckLen->Call($len);
    $_[0] = unpack('L', $len);
}
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Of course, you could also try the prototype method of loading your function.

yea i tried this wiwth pack/unpack the only issue i have is with initialisation of len=0 : in my c function i have a check: if len==0 return ERROR, but this doesnt get called ..? thx

GrandFather restored original content

yea i tried this with pack/unpack the only issue i have is with initialisation of len=0 : in my c function i have a check: if len==0 return ERROR, but this doesnt get called ..? thx

GrandFather restored original content

len is will never be NULL pointer. It'll never be zero. If you want the ability to pass NULL, we'll have to do more work. Which of the following is true?

• Did you mean to allow NULL to be passed?
• Did you forget to dereference len?
• Was choosing to pass a pointer a mistake?

And then there's return ERROR; in a function of return type void...

Show your code, not a description