gh-89488: Add warning about `Py_BuildValue("p")` needing exact `int` (GH-135610)

diff --git a/Doc/c-api/arg.rst b/Doc/c-api/arg.rst
index 49dbc8d71cce621291d908200dd8e7e02941e9d5..ab9f9c4539ae9a0b691a5f23a26dbff511a9b5c8 100644 (file)
--- a/Doc/c-api/arg.rst
+++ b/Doc/c-api/arg.rst
@@ -686,6 +686,12 @@ Building values
    ``p`` (:class:`bool`) [int]
       Convert a C :c:expr:`int` to a Python :class:`bool` object.
 
+      Be aware that this format requires an ``int`` argument.
+      Unlike most other contexts in C, variadic arguments are not coerced to
+      a suitable type automatically.
+      You can convert another type (for example, a pointer or a float) to a
+      suitable ``int`` value using ``(x) ? 1 : 0`` or ``!!x``.
+
       .. versionadded:: 3.14
 
    ``c`` (:class:`bytes` of length 1) [char]