1From d55b6b1fa87700f3eae3a29522972d2e7be7d53e Mon Sep 17 00:00:00 2001
2From: Khem Raj <raj.khem@gmail.com>
3Date: Sat, 14 Jan 2023 10:11:35 -0800
4Subject: [PATCH] use _Alignof to avoid UB in ALIGNOF
5
6WG14 N2350 clearly says that it is an UB having type definitions
7within "offsetof" [1]. Clang 16+ has started diagnosing it [2].
8This 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
16Upstream-Status: Submitted [https://gitlab.freedesktop.org/xorg/lib/libxcb/-/merge_requests/42]
17Signed-off-by: Khem Raj <raj.khem@gmail.com>
18---
19 src/c_client.py | 3 +--
20 1 file changed, 1 insertion(+), 2 deletions(-)
21
22diff --git a/src/c_client.py b/src/c_client.py
23index 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--
442.39.0
45
46