Additionally, is there a perlapi that will say what it thinks the type of THIS is?

You can find out what ST(0) is with: 
warn("ST(0) is of type %s\n", HvNAME(SvSTASH(SvRV(ST(0)))));

[download]
A demo: 
use Inline C => Config =>
    BUILD_NOISY => 1;

use Inline C => <<'EOC';

void foo(SV * x) {
    dXSARGS;
    if (sv_isobject(ST(0)))
        warn("ST(0) is of type %s\n", HvNAME(SvSTASH(SvRV(ST(0)))));
    else warn("Not an object\n");
    XSRETURN(0);
}


EOC

use Math::BigInt;
my $obj = Math::BigInt->new(17);
foo($obj);

[download]
Cheers,
Rob

In reply to Re: sv_derived_from gives a confsing result by syphilis
in thread sv_derived_from gives a confsing result by geoffleach

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