WG14 N2350 made very clear that it is an UB having type definitions within "offsetof" [1]. This patch enhances the implementation of macro alignof_slot to use builtin "_Alignof" to avoid undefined behavior on when using std=c11 or newer
clang 16+ has started to flag this [2] Fixes build when using -std >= gnu11 and using clang16+ [1] https://www.open-std.org/jtc1/sc22/wg14/www/docs/n2350.htm [2] https://reviews.llvm.org/D133574 Signed-off-by: Khem Raj <raj.k...@gmail.com> --- ChangeLog | 5 +++++ lib/alignof.h | 2 ++ 2 files changed, 7 insertions(+) diff --git a/ChangeLog b/ChangeLog index fb467a3c14..71d7f7b7f6 100644 --- a/ChangeLog +++ b/ChangeLog @@ -1,3 +1,8 @@ +2023-01-15 Khem Raj <raj.k...@gmail.com> + + * lib/alignof.h (alignof_slot): Use _Alignof when using C11 or newer + standard. + 2023-01-14 Bruno Haible <br...@clisp.org> error, verror tests: Fix link error when the package uses libintl. diff --git a/lib/alignof.h b/lib/alignof.h index 505ad97aa4..66a9496518 100644 --- a/lib/alignof.h +++ b/lib/alignof.h @@ -28,6 +28,8 @@ #if defined __cplusplus template <class type> struct alignof_helper { char __slot1; type __slot2; }; # define alignof_slot(type) offsetof (alignof_helper<type>, __slot2) +#elif defined(__STDC_VERSION__) && __STDC_VERSION__ >= 201112L && !defined(__cplusplus) +# define alignof_slot(type) _Alignof(type) #else # define alignof_slot(type) offsetof (struct { char __slot1; type __slot2; }, __slot2) #endif -- 2.39.0
