More info about the cycle detector.
diff --git a/Doc/ext/extending.tex b/Doc/ext/extending.tex
index a0a0440..0051a02 100644
--- a/Doc/ext/extending.tex
+++ b/Doc/ext/extending.tex
@@ -1248,10 +1248,12 @@
them so long as there are no finalizers implemented in Python
(\method{__del__()} methods). When there are such finalizers, the
detector exposes the cycles through the \ulink{\module{gc}
-module}{../lib/module-gc.html}. The \module{gc} module also exposes
+module}{../lib/module-gc.html} (specifically, the \code{garbage}
+variable in that module). The \module{gc} module also exposes a way
+to run the detector (the \function{collect()} function), as well as
configuration interfaces and the ability to disable the detector at
runtime. The cycle detector is considered an optional component;
-though it is included by default, it can be disabled at compile time
+though it is included by default, it can be disabled at build time
using the \longprogramopt{without-cycle-gc} option to the
\program{configure} script on \UNIX{} platforms (including Mac OS X)
or by removing the definition of \code{WITH_CYCLE_GC} in the