From e615eeeef2ce65cd156253e6068e2bce303ccfc8 Mon Sep 17 00:00:00 2001
From: Mathias Berchtold <mberchtold@gmail.com>
Date: Sat, 21 Feb 2026 15:01:11 -0700
Subject: Add MSVC support for Z_UNREACHABLE macro

Add Z_UNREACHABLE fallback for MSVC, as the C23 unreachable macro is not yet defined in the Windows SDK's <stddef.h>.
---
 zbuild.h | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/zbuild.h b/zbuild.h
index 39903d2176..c6a54e0f1e 100644
--- a/zbuild.h
+++ b/zbuild.h
@@ -53,7 +53,11 @@
 /* Hint to compiler that a block of code is unreachable, typically in a switch default condition */
 #ifndef Z_UNREACHABLE
 #  if defined(__STDC_VERSION__) && __STDC_VERSION__ >= 202311L
-#    define Z_UNREACHABLE() unreachable()           // C23 approach
+#    if !defined(unreachable) && defined(_MSC_VER)
+#      define Z_UNREACHABLE() __assume(0)
+#    else
+#      define Z_UNREACHABLE() unreachable()           // C23 approach
+#    endif
 #  elif (defined(__GNUC__) && (__GNUC__ >= 5)) || defined(__clang__)
 #    define Z_UNREACHABLE() __builtin_unreachable()
 #  else
-- 
cgit 0.0.5-2-1-g0f52