use strict;
use warnings;

use Inline C => <<'EOC';

/* As the function appears in AnyInt.pm */
long calc_32bit_signed_in_C(long input) {
  return (int32_t)((int32_t)input);
}

/* The same function, renamed to begin with an
   underscore, and return type altered to int */
int _calc_32bit_signed_in_C(int input) {
  return (int32_t)((int32_t)input);
}

EOC

print calc_32bit_signed_in_C(1073741824 + 1073741824), "\n";
print _calc_32bit_signed_in_C(1073741824 + 1073741824), "\n";

__END__

Outputs:
-2147483648
-2147483648