[pypy-commit] pypy default: Expand the docs

[arigo]

Author: Armin Rigo <arigo at tunes.org>
Branch: 
Changeset: r76670:2485283de005
Date: 2015-04-01 12:06 +0200
http://bitbucket.org/pypy/pypy/changeset/2485283de005/

Log:	Expand the docs

diff --git a/rpython/rlib/rgc.py b/rpython/rlib/rgc.py
--- a/rpython/rlib/rgc.py
+++ b/rpython/rlib/rgc.py
@@ -678,7 +678,12 @@
     """ This function does not do anything, but called from any annotated
     place, will tell that "func" is used to trace GC roots inside any instance
     of the type TP.  The func must be specified as "lambda: func" in this
-    call, for internal reasons.
+    call, for internal reasons.  Note that the func will be automatically
+    specialized on the 'callback' argument value.  Example:
+
+        def customtrace(gc, obj, callback, arg):
+            gc._trace_callback(callback, arg, obj + offset_of_x)
+        lambda_customtrace = lambda: customtrace
     """
 
 class RegisterGcTraceEntry(ExtRegistryEntry):