How do I tell XS that a reference OR undef is OK for a parameter (c)?

I think I would just pass c to the XSub as an SV, and then let the XSub determine whether c is a reference or not ( using SvROK(c) ). Once the XSub knows what it has, you can then have it take whatever steps are needed to pass satisfactory values on to the C routine.
If the XSub needs to know whether c is an object or not, use sv_isobject(c): 
use warnings;
use Math::BigInt;
use strict;

use Inline C => Config =>
    BUILD_NOISY => 1,
    USING => 'ParseRegExp';  


use Inline C => <<'END';

int is_ref(SV * x) {
    if(SvROK(x)) return 1;
    return 0;
}

int is_obj(SV * x) {
    if(sv_isobject(x)) return 1;
    return 0;
}

END

my $undef;
my $ref = \$undef;
my $obj = Math::BigInt->new(0);

for($undef, $ref, $obj) {
   print is_ref($_), " ", is_obj($_), "\n";
}

# Output:
# 0 0
# 1 0
# 1 1

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In reply to Re: XS: How to enable passing ref or undef? by syphilis
in thread XS: How to enable passing ref or undef? by tlhackque

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