Description:
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From user note 110923:

I think there's a bug in the sample code.

If curl_multi_select() returns -1, the do..while loop just keeps calling it until it returns something else.

So if repeated calles to curl_multi_select() can return -1 indefinitely (and the comments on the manual page for that function suggest it can), then the example code will just go into an infinite loop.

I'd post a fixed version, but I'm not sure what a return value of -1 actually implies:  Does it mean the entire multi-stack has failed somehow, or can we continue calling curl_mulit_exec()?