| Andrew Geissler | c5535c9 | 2023-01-27 16:10:19 -0600 | [diff] [blame^] | 1 | From d55b6b1fa87700f3eae3a29522972d2e7be7d53e Mon Sep 17 00:00:00 2001 |
| 2 | From: Khem Raj <raj.khem@gmail.com> |
| 3 | Date: Sat, 14 Jan 2023 10:11:35 -0800 |
| 4 | Subject: [PATCH] use _Alignof to avoid UB in ALIGNOF |
| 5 | |
| 6 | WG14 N2350 clearly says that it is an UB having type definitions |
| 7 | within "offsetof" [1]. Clang 16+ has started diagnosing it [2]. |
| 8 | This patch changes the implementation of macro |
| 9 | "ALIGNOF" to builtin "_Alignof" to avoid undefined behavior. |
| 10 | |
| 11 | _Alignof() return the ABI required minimum alignment. |
| 12 | |
| 13 | [1] https://www.open-std.org/jtc1/sc22/wg14/www/docs/n2350.htm |
| 14 | [2] https://reviews.llvm.org/D133574 |
| 15 | |
| 16 | Upstream-Status: Submitted [https://gitlab.freedesktop.org/xorg/lib/libxcb/-/merge_requests/42] |
| 17 | Signed-off-by: Khem Raj <raj.khem@gmail.com> |
| 18 | --- |
| 19 | src/c_client.py | 3 +-- |
| 20 | 1 file changed, 1 insertion(+), 2 deletions(-) |
| 21 | |
| 22 | diff --git a/src/c_client.py b/src/c_client.py |
| 23 | index fd256f0..4e48f13 100644 |
| 24 | --- a/src/c_client.py |
| 25 | +++ b/src/c_client.py |
| 26 | @@ -288,7 +288,6 @@ def c_open(self): |
| 27 | _c('#include "%s.h"', _ns.header) |
| 28 | |
| 29 | _c('') |
| 30 | - _c('#define ALIGNOF(type) offsetof(struct { char dummy; type member; }, member)') |
| 31 | |
| 32 | if _ns.is_ext: |
| 33 | for (n, h) in self.direct_imports: |
| 34 | @@ -1266,7 +1265,7 @@ def _c_serialize_helper_fields(context, self, |
| 35 | count += 1 |
| 36 | |
| 37 | code_lines.append( |
| 38 | - '%s xcb_align_to = ALIGNOF(%s);' |
| 39 | + '%s xcb_align_to = _Alignof(%s);' |
| 40 | % (space, |
| 41 | 'char' |
| 42 | if field.c_field_type == 'void' or field.type.is_switch |
| 43 | -- |
| 44 | 2.39.0 |
| 45 | |