From: Nathan Moinvaziri <nathan@nathanm.com>
Date: Sat, 10 Jan 2026 01:38:55 +0000 (-0800)
Subject: __builtin_bitreverse16 CMake compiler check fails for GCC 13
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=369ae91066bad2595c64475c99a129d8f2e03659;p=thirdparty%2Fzlib-ng.git

__builtin_bitreverse16 CMake compiler check fails for GCC 13

Provide a final check for __builtin_bitreverse16 in code.
---

diff --git a/fallback_builtins.h b/fallback_builtins.h
index 3b477abd3..0e6a1f1e1 100644
--- a/fallback_builtins.h
+++ b/fallback_builtins.h
@@ -42,6 +42,14 @@ Z_FORCEINLINE static int __builtin_ctzll(unsigned long long value) {
 
 #endif // _MSC_VER && !__clang__
 
+/* Double-check whether or not __builtin_bitreverse16 is available. It
+   may not be defined unless compiled for arch. */
+#if !defined(HAVE_BUILTIN_BITREVERSE16) && defined(__has_builtin)
+#  if __has_builtin(__builtin_bitreverse16)
+#    define HAVE_BUILTIN_BITREVERSE16
+#  endif
+#endif
+
 #ifndef HAVE_BUILTIN_BITREVERSE16
 
 #  ifdef __loongarch__