"The setting of errno after a successful call to a function is
unspecified unless the description of that function specifies that
errno shall not be modified."
However, free() in IEEE Std 1003.1-2008 does not mention its interaction
with errno, so MAY modify it after successful call
(it depends on particular free() implementation, OS-specific, etc.).
So, save errno across free() calls to make code portable and
POSIX-conformant.
2) Remove unused serrno assignment.
MFC after: 1 week
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