Incorrect IFUNC use in libpthread for fork, vfork wrapper [BZ #19861]

[Andreas Schwab]

The usual problem with a non-tail-call vfork is that subsequent calls in
the child overwrite the return address on the stack so that when vfork
returns the second time it doesn't return to the original caller in the
parent.  That doesn't necessarily lead to a crash, but you get a wrong
control flow.

Andreas.

-- 
Andreas Schwab, SUSE Labs, schwab@suse.de
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