From f7797077732dba4590eecd184ca5e4d9ca603d28 Mon Sep 17 00:00:00 2001
From: archo5 <1819544+archo5@users.noreply.github.com>
Date: Mon, 25 May 2026 20:57:37 +0300
Subject: [PATCH] added a missing feature check ifdef for is_constant_evaluated

needed for VS2017+x64 support
---
 zmij.cc | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/zmij.cc b/zmij.cc
index 5e07cc4..c5bc81b 100644
--- a/zmij.cc
+++ b/zmij.cc
@@ -282,14 +282,16 @@ constexpr auto umul128(uint64_t x, uint64_t y) noexcept -> uint128_t {
 #if ZMIJ_USE_INT128
   return uint128_t(x) * y;
 #else
-#  if defined(_M_AMD64)
+#  ifdef __cpp_lib_is_constant_evaluated
+#    if defined(_M_AMD64)
   if (!__builtin_is_constant_evaluated()) {
     uint64_t hi = 0;
     uint64_t lo = _umul128(x, y, &hi);
     return {hi, lo};
   }
-#  elif defined(_M_ARM64)
+#    elif defined(_M_ARM64)
   if (!__builtin_is_constant_evaluated()) return {__umulh(x, y), x * y};
+#    endif
 #  endif
   uint64_t a = x >> 32;
   uint64_t b = uint32_t(x);