gh-141370: document undefined behavior of Py_ABS() (GH-141439)

diff --git a/Doc/c-api/intro.rst b/Doc/c-api/intro.rst
index 6e1a9dcb35543bb3e1defdd325be76dfbb05a45b..c76cc2f70ecccffebd9edfcf5ba056e5a07d4e46 100644 (file)
--- a/Doc/c-api/intro.rst
+++ b/Doc/c-api/intro.rst
@@ -121,6 +121,10 @@ complete listing.
 
    Return the absolute value of ``x``.
 
+   If the result cannot be represented (for example, if ``x`` has
+   :c:macro:`!INT_MIN` value for :c:expr:`int` type), the behavior is
+   undefined.
+
    .. versionadded:: 3.3
 
 .. c:macro:: Py_ALWAYS_INLINE