From 307c02ed698a69763ef1c9c0df4ff24727442118 Mon Sep 17 00:00:00 2001
From: Lasse Collin <lasse.collin@tukaani.org>
Date: Sat, 29 Mar 2025 12:41:32 +0200
Subject: [PATCH] sysdefs.h: Avoid <stdalign.h> even with C11 compilers

Oracle Developer Studio 12.6 on Solaris 10 claims C11 support in
__STDC_VERSION__ and supports _Alignas. However, <stdalign.h> is missing.
We only need alignas, so define it to _Alignas with C11/C17 compilers.
If something included <stdalign.h> later, it shouldn't cause problems.

Thanks to Ihsan Dogan for reporting the issue and testing the fix.

Fixes: c0e7eaae8d6eef1e313c9d0da20ccf126ec61f38
---
 src/common/sysdefs.h | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/src/common/sysdefs.h b/src/common/sysdefs.h
index 8e01bd17..b10ffa7c 100644
--- a/src/common/sysdefs.h
+++ b/src/common/sysdefs.h
@@ -172,7 +172,9 @@ typedef unsigned char _Bool;
 #if __STDC_VERSION__ >= 202311
 	// alignas is a keyword in C23. Do nothing.
 #elif __STDC_VERSION__ >= 201112
-#	include <stdalign.h>
+	// Oracle Developer Studio 12.6 lacks <stdalign.h>.
+	// For simplicity, avoid the header with all C11/C17 compilers.
+#	define alignas _Alignas
 #elif defined(__GNUC__) || defined(__clang__)
 #	define alignas(n) __attribute__((__aligned__(n)))
 #else