https://gcc.gnu.org/bugzilla/show_bug.cgi?id=89299
--- Comment #5 from Jonathan Wakely <redi at gcc dot gnu.org> ---
For now I suggest this patch for the docs:
--- a/gcc/doc/extend.texi
+++ b/gcc/doc/extend.texi
@@ -6815,6 +6815,11 @@ does not allow the exception to be caught, only to
perform an action.
It is undefined what happens if @var{cleanup_function} does not
return normally.
+In C++ the @var{cleanup_function} must be a normal function.
+Other types of callable such as a function templates,
+lambda expressions or function objects with @code{operator()}
+are not supported.
+
@item common
@itemx nocommon
@cindex @code{common} variable attribute
