Ruby 1.9.3 is driving me insane

gistfile1.txt

# extconf.rb
require 'mkmf'
$CFLAGS += " -std=c99" # Doesn't help
create_makefile('foo')

# foo.c
#include "ruby.h"

static VALUE foo_bar(VALUE self){
  const char* bar = "bar";
  printf("We here?\n");
  VALUE val = rb_str_new2(bar);

  return val;
}

void Init_foo(){
  VALUE cFoo = rb_define_class("Foo", rb_cObject);

  rb_define_method(cFoo, "bar", foo_bar, 0);
}

# Output of ruby-1.9.3-p194 when I run "ruby extconf.rb"
foo.c: In function ‘foo_bar’:
foo.c:6: warning: ISO C90 forbids mixed declarations and code