If the platform supports the \function{putenv()} function, this
mapping may be used to modify the environment as well as query the
environment. \function{putenv()} will be called automatically when
-the mapping is modified.
+the mapping is modified. \note{On some platforms, including
+FreeBSD and Mac OS X, setting \code{environ} may cause memory leaks.
+Refer to the system documentation for putenv.}
If \function{putenv()} is not provided, this mapping may be passed to
the appropriate process-creation functions to cause child processes to
\function{fork()} and \function{execv()}.
Availability: most flavors of \UNIX, Windows.
+\note{On some platforms, including FreeBSD and Mac OS X,
+setting \code{environ} may cause memory leaks.
+Refer to the system documentation for putenv.}
+
When \function{putenv()} is
supported, assignments to items in \code{os.environ} are automatically
translated into corresponding calls to \function{putenv()}; however,