Random memory corruption on the Linux bots

[catamorphism]

For example: http://buildbot.rust-lang.org/builders/auto-linux-64-nopt-t/builds/1193/steps/test/logs/stdio

I don't think the change that I made in this commit ( #10002 ) could have caused this problem.

[alexcrichton]

Closing, I don't think this is too actionable any more.