I found if the dns loopup is slow, my libcurl request will block my Application’s main thread for seconds.
It makes me guess that my libcurl.a(from cocos2dx package) has async DNS support or not?
This isn’t a big problem(I’ve already solved the dns loopup speed problem), I just want to confirm it.
I am not sure. We just built from source code.
Now, the build project in my personal repo. It is not easy to build with SSL support. We will move all 3rd libraries into another repo someday.
Is there anyway to make sure if it is supported or not?
Thx for reply 
Refer to libcurl website, I see how to build libcurl with c-ares.
That is when build libcurl we need configure with “–enable-ares”.
So as you said, built from source code without any other options maybe not include the c-ares support. This answers the question I make.
Reference is here:
http://curl.haxx.se/dev/readme-ares.html
Thank you for your team’s nice job for build these libraries. They work very well in my project.
Thanks for the information.
We will try to find a way if it can be build without Android source code, which is not convenient.