extconf.rb in raindrops-0.4.0

- old
+ new

@@ -5,7 +5,33 @@
 have_func('munmap', 'sys/mman.h') or abort 'munmap() not found'
 
 have_func("rb_struct_alloc_noinit")
 have_func('rb_thread_blocking_region')
 
+checking_for "GCC 4+ atomic builtins" do
+  src = <<SRC
+int main(int argc, char * const argv[]) {
+        volatile unsigned long i = 0;
+        __sync_add_and_fetch(&i, argc);
+        __sync_sub_and_fetch(&i, argc);
+        return 0;
+}
+SRC
+
+  if try_run(src)
+    $defs.push(format("-DHAVE_GCC_ATOMIC_BUILTINS"))
+    true
+  else
+    false
+  end
+end or have_header('atomic_ops.h') or abort <<-SRC
+
+libatomic_ops is required if GCC 4+ is not used.
+See http://www.hpl.hp.com/research/linux/atomic_ops/
+
+Users of Debian-based distros may run:
+
+  apt-get install libatomic-ops-dev
+SRC
+
 dir_config('raindrops')
 create_makefile('raindrops_ext')