Compiling geoip-c for ruby 2.0.0 vs 1.9.3 mkmf error

for_1.9.3.c

// Compile with:
// export RUBY_DIR=$HOME/.rvm/rubies/ruby-1.9.3-p448
// gcc-4.6 -o for_1.9.3 -I$RUBY_DIR/include/ruby-1.9.1/x86_64-darwin12.4.1 -I$RUBY_DIR/include/ruby-1.9.1/ruby/backward -I$RUBY_DIR/include/ruby-1.9.1 -Iext/geoip -D_XOPEN_SOURCE -D_DARWIN_C_SOURCE   -I/usr/local/opt/libyaml/include -I/usr/local/opt/readline/include -I/usr/local/opt/libksba/include -I/usr/local/opt/openssl/include  -O3 -ggdb -Wall -Wextra -Wno-unused-parameter -Wno-parentheses -Wno-long-long -Wno-missing-field-initializers -Wpointer-arith -Wwrite-strings -Wdeclaration-after-statement -Wimplicit-function-declaration  -fno-common -pipe  for_1.9.3.c  -L. -L$RUBY_DIR/lib -L/usr/local/opt/libyaml/lib -L/usr/local/opt/readline/lib -L/usr/local/opt/libksba/lib -L/usr/local/opt/openssl/lib -L.  -L/usr/local/opt/libyaml/lib -L/usr/local/opt/readline/lib -L/usr/local/opt/libksba/lib -L/usr/local/opt/openssl/lib -liconv  -lruby.1.9.1 -lGeoIP -liconv  -lpthread -ldl -lobjc

#include "ruby.h"

int t() { GeoIP_record_by_ipnum(); return 0; }
int main(int argc, char **argv)
{
  if (argc > 1000000) {
    printf("%p", &t);
  }

  return 0;
}

for_2.0.0.c

// Compile with
// export RUBY_DIR=$HOME/.rvm/rubies/ruby-2.0.0-p247
// /usr/bin/clang -o for_2.0.0 -I$RUBY_DIR/include/ruby-2.0.0/x86_64-darwin12.3.0 -I$RUBY_DIR/include/ruby-2.0.0/ruby/backward -I$RUBY_DIR/include/ruby-2.0.0 -Iext/geoip -D_XOPEN_SOURCE -D_DARWIN_C_SOURCE -D_DARWIN_UNLIMITED_SELECT -D_REENTRANT   -O3 -I/Users/mpapis/.sm/pkg/active/include -fPIC -pipe  for_2.0.0.c  -L. -L$RUBY_DIR/lib -L. -Z -L/Users/mpapis/.sm/pkg/active/lib -L/usr/lib -fPIC -Bstatic -fstack-protector    -arch x86_64  -liconv  -lruby-static -lGeoIP -liconv  -lpthread -ldl -lobjc

#include "ruby.h"

extern int t(void);
int t(void) { void ((*volatile p)()); p = (void ((*)()))GeoIP_record_by_ipnum; return 0; }
int main(int argc, char **argv)
{
  if (argc > 1000000) {
    printf("%p", &t);
  }

  return 0;
}