gh-102013: Add PyUnstable_GC_VisitObjects (#102014)

1 files changed, 33 insertions, 0 deletions

diff --git a/Doc/c-api/gcsupport.rst b/Doc/c-api/gcsupport.rst
index 8c90d1e..cb5d64a 100644
--- a/Doc/c-api/gcsupport.rst
+++ b/Doc/c-api/gcsupport.rst
@@ -228,3 +228,36 @@ garbage collection runs.
    Returns the current state, 0 for disabled and 1 for enabled.
 
    .. versionadded:: 3.10
+
+
+Querying Garbage Collector State
+--------------------------------
+
+The C-API provides the following interface for querying information about
+the garbage collector.
+
+.. c:function:: void PyUnstable_GC_VisitObjects(gcvisitobjects_t callback, void *arg)
+
+   Run supplied *callback* on all live GC-capable objects. *arg* is passed through to
+   all invocations of *callback*.
+
+   .. warning::
+      If new objects are (de)allocated by the callback it is undefined if they
+      will be visited.
+
+      Garbage collection is disabled during operation. Explicitly running a collection
+      in the callback may lead to undefined behaviour e.g. visiting the same objects
+      multiple times or not at all.
+
+   .. versionadded:: 3.12
+
+.. c:type:: int (*gcvisitobjects_t)(PyObject *object, void *arg)
+
+   Type of the visitor function to be passed to :c:func:`PyUnstable_GC_VisitObjects`.
+   *arg* is the same as the *arg* passed to ``PyUnstable_GC_VisitObjects``.
+   Return ``0`` to continue iteration, return ``1`` to stop iteration. Other return
+   values are reserved for now so behavior on returning anything else is undefined.
+
+   .. versionadded:: 3.12
+
+