bpo-35461: Document C API functions which suppress exceptions. (GH-11119)

diff --git a/Doc/c-api/objbuffer.rst b/Doc/c-api/objbuffer.rst
index e7f4fde..9ad7c57 100644
--- a/Doc/c-api/objbuffer.rst
+++ b/Doc/c-api/objbuffer.rst
@@ -39,7 +39,11 @@
 .. c:function:: int PyObject_CheckReadBuffer(PyObject *o)
 
    Returns ``1`` if *o* supports the single-segment readable buffer interface.
-   Otherwise returns ``0``.
+   Otherwise returns ``0``.  This function always succeeds.
+
+   Note that this function tries to get and release a buffer, and exceptions
+   which occur while calling correspoding functions will get suppressed.
+   To get error reporting use :c:func:`PyObject_GetBuffer()` instead.
 
 
 .. c:function:: int PyObject_AsWriteBuffer(PyObject *obj, void **buffer, Py_ssize_t *buffer_len)