From 3811bbf6e026b93e18aaeb06df7a073acb716354 Mon Sep 17 00:00:00 2001
From: Dusk_NM02 <Dusk.11th@outlook.com>
Date: Sun, 23 Feb 2025 16:03:59 +0800
Subject: [PATCH] Fix popcnt cause crashes on unsupported devices

---
 CMakeLists.txt        | 8 ++++++++
 lib/nghttp3_ringbuf.c | 5 +++--
 2 files changed, 11 insertions(+), 2 deletions(-)

diff --git a/CMakeLists.txt b/CMakeLists.txt
index b78ab52..dcc85c0 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -179,6 +179,12 @@ foreach(name
   configure_file("${name}.in" "${name}" @ONLY)
 endforeach()
 
+option(ENABLE_POPCNT "Enable popcnt instruction" ON)
+
+if(NOT ENABLE_POPCNT)
+  add_definitions(-DDISABLE_POPCNT)
+endif()
+
 if(ENABLE_SHARED_LIB AND ENABLE_STATIC_LIB AND MSVC AND NOT STATIC_LIB_SUFFIX)
   set(STATIC_LIB_SUFFIX "_static")
 endif()
@@ -213,6 +219,8 @@ message(STATUS "summary of build options:
       CXXFLAGS:       ${CMAKE_CXX_FLAGS_${_build_type}} ${CMAKE_CXX_FLAGS}
       WARNCFLAGS:     ${WARNCFLAGS}
       WARNCXXFLAGS:   ${WARNCXXFLAGS}
+    SIMD instruction:
+      Enable popcnt:  ${ENABLE_POPCNT}
     Library:
       Shared:         ${ENABLE_SHARED_LIB}
       Static:         ${ENABLE_STATIC_LIB}
diff --git a/lib/nghttp3_ringbuf.c b/lib/nghttp3_ringbuf.c
index 85c2e03..9bea0f5 100644
--- a/lib/nghttp3_ringbuf.c
+++ b/lib/nghttp3_ringbuf.c
@@ -35,8 +35,9 @@
 
 #ifndef NDEBUG
 static int ispow2(size_t n) {
-#  if defined(_MSC_VER) && !defined(__clang__) &&                              \
-    (defined(_M_ARM) || (defined(_M_ARM64) && _MSC_VER < 1941))
+#  if defined(DISABLE_POPCNT) ||                                               \
+    (defined(_MSC_VER) && !defined(__clang__) &&                               \
+    (defined(_M_ARM) || (defined(_M_ARM64) && _MSC_VER < 1941)))
   return n && !(n & (n - 1));
 #  elif defined(WIN32)
   return 1 == __popcnt((unsigned int)n);