From 3d3d91ac1db8ee7f624d225734cb5b57b752e00b Mon Sep 17 00:00:00 2001
From: Khem Raj <raj.khem@gmail.com>
Date: Sun, 15 Jan 2023 00:16:25 -0800
Subject: [PATCH] Define alignof using _Alignof when using C11 or newer

WG14 N2350 made very clear that it is an UB having type definitions
within "offsetof" [1]. This patch enhances the implementation of macro
alignof 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+

Older compilers gcc < 4.9 or clang < 8 has buggy _Alignof even though it
may support C11, exclude those compilers too

[1] https://www.open-std.org/jtc1/sc22/wg14/www/docs/n2350.htm
[2] https://reviews.llvm.org/D133574

Upstream-Status: Pending
Signed-off-by: Khem Raj <raj.khem@gmail.com>
---
 libiberty/sha1.c | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/libiberty/sha1.c b/libiberty/sha1.c
index 49e8e0b6c2b..72de5cc8ad6 100644
--- a/libiberty/sha1.c
+++ b/libiberty/sha1.c
@@ -234,7 +234,17 @@ sha1_process_bytes (const void *buffer, size_t len, struct sha1_ctx *ctx)
   if (len >= 64)
     {
 #if !_STRING_ARCH_unaligned
+/* GCC releases before GCC 4.9 had a bug in _Alignof.  See GCC bug 52023
+   <https://gcc.gnu.org/bugzilla/show_bug.cgi?id=52023>.
+   clang versions < 8.0.0 have the same bug.  */
+#if (!defined __STDC_VERSION__ || __STDC_VERSION__ < 201112 \
+     || (defined __GNUC__ && __GNUC__ < 4 + (__GNUC_MINOR__ < 9) \
+	&& !defined __clang__) \
+     || (defined __clang__ && __clang_major__ < 8))
 # define alignof(type) offsetof (struct { char c; type x; }, x)
+#else
+# define alignof(type) _Alignof(type)
+#endif
 # define UNALIGNED_P(p) (((size_t) p) % alignof (sha1_uint32) != 0)
       if (UNALIGNED_P (buffer))
 	while (len > 64)
