Sigh... The crash is a subprocess started with fork is not entirely unexpected, although I had hoped that the current version of _scproxy would be safe enough.

A number of Apple frameworks detect that a process called fork after they initialized and then explictly crash (basicly a call to abort()). In this case it appears to just not work correctly.

I'm not sure how to fix this, other than spawning a small helper program to query the proxy settings. That could get prohibitively expensive when fetching a lot of URLs though (and an RPC system might run into the a similar problem after calling fork...)