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Relatively large expansion of the docs for gc.garbage.

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Tim Peters 2001-11-18 04:51:17 +00:00
parent 36515e28ed
commit af0a883041
1 changed files with 19 additions and 5 deletions
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24
Doc/lib/libgc.tex
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@ -79,7 +79,8 @@ Return the current collection thresholds as a tuple of
\end{funcdesc}
The following variable is provided for read-only access:
The following variable is provided for read-only access (you can
mutate its value but should not rebind it):
\begin{datadesc}{garbage}
A list of objects which the collector found to be unreachable
@ -88,9 +89,22 @@ contains only objects with \method{__del__()} methods.\footnote{Prior to
Python 2.2, the list contained all instance objects in unreachable
cycles, not only those with \method{__del__()} methods.}
Objects that have
\method{__del__()} methods and create part of a reference cycle cause
the entire reference cycle to be uncollectable. If
\constant{DEBUG_SAVEALL} is set, then all unreachable objects will
\method{__del__()} methods and are part of a reference cycle cause
the entire reference cycle to be uncollectable, including objects
not necessarily in the cycle but reachable only from it. Python doesn't
collect such cycles automatically because, in general, it isn't possible
for Python to guess a safe order in which to run the \method{__del__()}
methods. If you know a safe order, you can force the issue by examining
the \var{garbage} list, and explicitly breaking cycles due to your
objects within the list. Note that these objects are kept alive even
so by virtue of being in the \var{garbage} list, so they should be
removed from \var{garbage} too. For example, after breaking cycles, do
\code{del gc.garbage[:]} to empty the list. It's generally better
to avoid the issue by not creating cycles containing objects with
\method{__del__()} methods, and \var{garbage} can be examined in that
case to verify that no such are being created.
If \constant{DEBUG_SAVEALL} is set, then all unreachable objects will
be added to this list rather than freed.
\end{datadesc}
@ -132,5 +146,5 @@ a leaking program.
\begin{datadesc}{DEBUG_LEAK}
The debugging flags necessary for the collector to print
information about a leaking program (equal to \code{DEBUG_COLLECTABLE |
DEBUG_UNCOLLECTABLE | DEBUG_INSTANCES | DEBUG_OBJECTS | DEBUG_SAVEALL}).
DEBUG_UNCOLLECTABLE | DEBUG_INSTANCES | DEBUG_OBJECTS | DEBUG_SAVEALL}).
\end{datadesc}