diff --git a/CMakeLists.txt b/CMakeLists.txt
new file mode 100644
index 00000000..e4ccf834
--- /dev/null
+++ b/CMakeLists.txt
@@ -0,0 +1,216 @@
+cmake_minimum_required(VERSION 3.15)
+
+project(opennurbs CXX C)
+
+if(NOT "${CMAKE_CXX_STANDARD}")
+  # setting the C++ standard if not specified
+  if(DEFINED CMAKE_CXX20_STANDARD_COMPILE_OPTION
+     OR DEFINED CMAKE_CXX20_EXTENSION_COMPILE_OPTION)
+    set(CXX_LATEST_STANDARD 20)
+  elseif(DEFINED CMAKE_CXX17_STANDARD_COMPILE_OPTION
+         OR DEFINED CMAKE_CXX17_EXTENSION_COMPILE_OPTION)
+    set(CXX_LATEST_STANDARD 17)
+  elseif(DEFINED CMAKE_CXX14_STANDARD_COMPILE_OPTION
+         OR DEFINED CMAKE_CXX14_EXTENSION_COMPILE_OPTION)
+    set(CXX_LATEST_STANDARD 14)
+  else()
+    set(CXX_LATEST_STANDARD 11)
+  endif()
+  set(CMAKE_CXX_STANDARD ${CXX_LATEST_STANDARD})
+endif()
+message(STATUS "CMAKE_CXX_STANDARD: ${CXX_LATEST_STANDARD}")
+
+# opennurbs source
+file(GLOB opennurbs_SOURCE "${CMAKE_SOURCE_DIR}/*.h"
+     "${CMAKE_SOURCE_DIR}/*.cpp")
+# exclude the examples
+list(FILTER opennurbs_SOURCE EXCLUDE REGEX "${CMAKE_SOURCE_DIR}/example*")
+
+if(NOT CMAKE_SYSTEM_NAME STREQUAL "Windows")
+  list(REMOVE_ITEM opennurbs_SOURCE
+       "${CMAKE_SOURCE_DIR}/opennurbs_unicode_cp932.cpp")
+  list(REMOVE_ITEM opennurbs_SOURCE
+       "${CMAKE_SOURCE_DIR}/opennurbs_unicode_cp949.cpp")
+endif()
+
+# remove opennurbs_gl if no opengl
+find_package(OpenGL)
+if(NOT ${OPENGL_FOUND})
+  message(WARNING "OpenGL not found. Excluding opennurbs_gl")
+  list(REMOVE_ITEM opennurbs_SOURCE "${CMAKE_SOURCE_DIR}/opennurbs_gl.cpp")
+endif()
+
+# Build the opennurbs library
+option(OPENNURBS_SHARED "Build shared libraries" OFF)
+if(${OPENNURBS_SHARED})
+  # if dynamic
+
+  # opennurbs shared library
+  add_library(opennurbs SHARED ${opennurbs_SOURCE})
+
+  # define opennurbs_EXPORTS to compile as a shared library
+  target_compile_definitions(opennurbs PRIVATE OPENNURBS_EXPORTS
+                                               ON_COMPILING_OPENNURBS)
+
+  # define OPENNURBS_IMORTS for the usage of the library
+  message(
+    WARNING
+      "Define `OPENNURBS_IMORTS` when using the opennurbs.dll before including opennurbs_public.h\n  target_compile_definitions(main PUBLIC OPENNURBS_IMPORTS)"
+  )
+else()
+  # if static
+
+  if(CMAKE_SYSTEM_NAME STREQUAL "Windows")
+    add_library(opennurbs STATIC ${opennurbs_SOURCE})
+  else()
+    if(CMAKE_SYSTEM_NAME STREQUAL "Linux" OR CMAKE_SYSTEM_NAME STREQUAL
+                                             "Android")
+      # Include UUID source (bundled with opennurbs)
+      file(GLOB UUID_SRC "${CMAKE_SOURCE_DIR}/android_uuid/*.h"
+           "${CMAKE_SOURCE_DIR}/android_uuid/*.c")
+      list(REMOVE_ITEM UUID_SRC
+           "${CMAKE_SOURCE_DIR}/android_uuid/gen_uuid_nt.c")
+    endif()
+
+    # Need to combine all source files for static linking on non-windows
+    add_library(opennurbs STATIC ${UUID_SRC} ${opennurbs_SOURCE})
+  endif()
+
+  # define ON_COMPILING_OPENNURBS to compile as a static library
+  target_compile_definitions(opennurbs PRIVATE ON_COMPILING_OPENNURBS)
+endif()
+
+# compile definitions
+target_compile_definitions(
+  opennurbs
+  PRIVATE
+    OPENNURBS_INPUT_LIBS_DIR="${CMAKE_CURRENT_BINARY_DIR}/$<CONFIGURATION>"
+    UNICODE)
+
+if(CMAKE_SYSTEM_NAME STREQUAL "Windows")
+  # Windows specific
+
+  # Fix "WIN32" preprocessor definitions on x64
+  if(${CMAKE_SIZEOF_VOID_P} EQUAL "8")
+    message(STATUS "Removing WIN32 definition for 64 bit build of opennurbs")
+    string(REPLACE "/DWIN32" "" CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS}")
+    target_compile_definitions(opennurbs PRIVATE WIN64)
+  endif()
+elseif(CMAKE_SYSTEM_NAME STREQUAL "Linux")
+  # Linux specific
+
+  # Linux compiler definitions
+  target_compile_definitions(opennurbs PRIVATE ON_RUNTIME_LINUX)
+endif()
+
+if(CMAKE_CXX_COMPILER_ID MATCHES ".*Clang")
+  target_compile_definitions(opennurbs PRIVATE ON_COMPILER_CLANG)
+endif()
+
+# Dependencies
+
+# zlib
+option({OPENNURBS_EXTERNAL_ZLIB, "use external zlib package" OFF)
+if(${OPENNURBS_EXTERNAL_ZLIB} OR ${OPENNURBS_ZLIB_LIB_DIR})
+  message(STATUS "Using external ZLIB")
+  find_package(ZLIB REQUIRED)
+  target_link_libraries(opennurbs PRIVATE ZLIB::ZLIB)
+  target_compile_definitions(ZLIB::ZLIB PRIVATE MY_ZCALLOC Z_PREFIX)
+  get_target_property(OPENNURBS_ZLIB_LIB_DIR ZLIB::ZLIB
+                      LIBRARY_OUTPUT_DIRECTORY)
+  target_compile_definitions(
+    opennurbs PRIVATE OPENNURBS_ZLIB_LIB_DIR="${OPENNURBS_ZLIB_LIB_DIR}")
+else()
+  # build zlib (bundled with opennurbs)
+  file(GLOB ZLIB_SOURCE "${CMAKE_SOURCE_DIR}/zlib/*.h"
+       "${CMAKE_SOURCE_DIR}/zlib/*.c")
+  add_library(zlib ${ZLIB_SOURCE})
+  target_compile_definitions(zlib PRIVATE MY_ZCALLOC Z_PREFIX)
+  set_target_properties(
+    zlib PROPERTIES ARCHIVE_OUTPUT_DIRECTORY
+                    "${CMAKE_CURRENT_BINARY_DIR}/$<CONFIGURATION>")
+  set(opennurbs_ZLIB_LIB_DIR "${CMAKE_CURRENT_BINARY_DIR}/$<CONFIGURATION>")
+  target_compile_definitions(
+    opennurbs PRIVATE opennurbs_ZLIB_LIB_DIR=${opennurbs_ZLIB_LIB_DIR})
+  target_link_libraries(opennurbs PRIVATE zlib)
+endif()
+# zlib-specific flags for opennurbs
+target_compile_definitions(opennurbs PRIVATE MY_ZCALLOC Z_PREFIX)
+
+# shlwapi on windows
+if(CMAKE_SYSTEM_NAME STREQUAL "Windows")
+  target_link_libraries(opennurbs PRIVATE shlwapi)
+endif()
+
+# cross_dirent
+if(CMAKE_SYSTEM_NAME STREQUAL "Windows")
+  find_path(DIRENT_INCLUDE_DIR dirent.h)
+  if(${DIRENT_INCLUDE_DIR_FOUND})
+    target_include_directories(opennurbs PRIVATE ${DIRENT_INCLUDE_DIR_FOUND})
+  else()
+    file(DOWNLOAD https://github.com/tronkko/dirent/raw/1.23.2/include/dirent.h
+         ${CMAKE_CURRENT_BINARY_DIR}/_deps/dirent/include/dirent.h)
+    target_include_directories(
+      opennurbs PRIVATE "${CMAKE_CURRENT_BINARY_DIR}/_deps/dirent/include/")
+  endif()
+endif()
+
+# uuid with clang on non-linux, android, windows
+if(NOT CMAKE_SYSTEM_NAME STREQUAL "Linux"
+   AND NOT CMAKE_SYSTEM_NAME STREQUAL "Windows"
+   AND CMAKE_CXX_COMPILER_ID MATCHES ".*Clang")
+  # uuid/uuid.h is required by opennurbs
+  message(STATUS "Finding uuid library")
+  find_package(UUID QUIET)
+  if(${UUID_FOUND})
+    target_include_directories(opennurbs PRIVATE ${UUID_INCLUDE_DIRS})
+  else()
+    # find uuid manually
+    if(NOT UUID_INCLUDE_DIR)
+      find_path(UUID_INCLUDE_DIR uuid/uuid.h)
+    endif()
+    if(EXISTS "${UUID_INCLUDE_DIR}")
+      include(CheckCXXSymbolExists)
+
+      set(UUID_INCLUDE_DIRS ${UUID_INCLUDE_DIR})
+      set(CMAKE_REQUIRED_INCLUDES ${UUID_INCLUDE_DIRS})
+      check_cxx_symbol_exists("uuid_generate_random" "uuid/uuid.h"
+                              _uuid_header_only)
+      if(NOT _uuid_header_only AND NOT UUID_LIBRARY)
+        include(CheckLibraryExists)
+        check_library_exists("uuid" "uuid_generate_random" "" _have_libuuid)
+        if(_have_libuuid)
+          set(UUID_LIBRARY "uuid")
+        endif()
+      endif()
+    endif()
+
+    if(UUID_LIBRARY)
+      set(UUID_LIBRARIES ${UUID_LIBRARY})
+    endif()
+
+    unset(CMAKE_REQUIRED_INCLUDES)
+
+    include(FindPackageHandleStandardArgs)
+    find_package_handle_standard_args(uuid DEFAULT_MSG UUID_INCLUDE_DIR)
+
+    # finally include it
+    target_include_directories(opennurbs PRIVATE ${UUID_INCLUDE_DIRS})
+  endif()
+endif()
+
+# OpenGL
+if(${OPENGL_FOUND})
+  target_link_libraries(opennurbs PRIVATE OpenGL::GL OpenGL::GLU)
+endif()
+
+# Suppress -Wdefaulted-function-deleted on Clang
+if(CMAKE_CXX_COMPILER_ID MATCHES ".*Clang")
+  # TODO fix this
+  message(WARNING "Suppressing -Wdefaulted-function-deleted for opennurbs")
+  target_compile_options(opennurbs PRIVATE -Wno-defaulted-function-deleted)
+endif()
+
+# Set the outputs of opennurbs CMake
+set(opennurbs_LIBRARY ${opennurbs})
+set(opennurbs_INCLUDE_DIR "${CMAKE_CURRENT_LIST_DIR}")
diff --git a/README.md b/README.md
index d86b8177..93e722cf 100644
--- a/README.md
+++ b/README.md
@@ -28,6 +28,54 @@ Please see ["Getting started"](https://developer.rhino3d.com/guides/opennurbs/ge
 
 There's also a collection of [example 3dm files](example_files/) available for testing.
 
+## Building Using CMake:
+
+1. Clone the repository 
+2. `cd` to the root directory of the repository.
+3. Run the following to configure the CMake files.
+```
+cmake -S ./ -B ./build -DCMAKE_FIND_FRAMEWORK=LAST
+```
+   
+   Note: if [ninja-build](https://ninja-build.org/) is installed, you can specify `Ninja` to speed up the build:
+   ```
+    cmake -S ./ -B ./build -G "Ninja Multi-Config" -DCMAKE_FIND_FRAMEWORK=LAST
+   ```
+   
+   Note: To use Ninja with the Visual Studio Compiler, open the MSVC command prompt (or run `vcvarsall.bat`), and run:
+   ```
+    cmake -S ./ -B ./build -G "Ninja Multi-Config" -D CMAKE_CXX_COMPILER=cl -D CMAKE_C_COMPILER=cl
+   ```
+
+   Note: `-DCMAKE_FIND_FRAMEWORK=LAST` fixes the issue of the MacOS compilers that choose an incorrect framework to build system headers.
+
+   Note: Additionally, pass `-A ARM64` to build for ARM64. 
+
+4. Finally, run the following to build the library.
+```
+cmake --build ./build --config Release
+```
+
+### Build as a shared library with CMake 
+
+To build as a DLL with Visual Studio, you should add `-DOPENNURBS_SHARED=ON` to the command of step `3`:
+```
+cmake -S ./ -B ./build -DOPENNURBS_SHARED=ON
+```
+
+or with Ninja
+```
+cmake -S ./ -B ./build -G "Ninja Multi-Config" -D CMAKE_CXX_COMPILER=cl -D CMAKE_C_COMPILER=cl -DOPENNURBS_SHARED=ON
+```
+
+Build as usual as we described in step 4.
+
+When using the dll, define `OPENNURBS_IMPORTS` before including `opennurbs_public.h`
+```cmake
+target_compile_definitions(main PUBLIC OPENNURBS_IMPORTS)
+```
+
+
 ## Questions?
 
 For technical support, please head over to [Discourse](https://discourse.mcneel.com/category/opennurbs).
diff --git a/opennurbs_defines.h b/opennurbs_defines.h
index fa156bae..35e2e0cf 100644
--- a/opennurbs_defines.h
+++ b/opennurbs_defines.h
@@ -2133,7 +2133,7 @@ class ON_CLASS ON
   // the values.  The reason for the gaps between the enum
   // values is to leave room for future snaps with prededence
   // falling between existing snaps
-  enum osnap_mode
+  enum osnap_mode: unsigned int
   {
     os_none          =          0,
     os_near          =          2,
@@ -2409,7 +2409,7 @@ class ON_CLASS ON_COMPONENT_INDEX
   // Do not change these values; they are stored in 3dm archives
   // and provide a persistent way to indentify components of
   // complex objects.
-  enum TYPE
+  enum TYPE: unsigned int
   {
     invalid_type       =   0,
 
diff --git a/opennurbs_file_utilities.cpp b/opennurbs_file_utilities.cpp
index 20e7e85d..e6e98719 100644
--- a/opennurbs_file_utilities.cpp
+++ b/opennurbs_file_utilities.cpp
@@ -37,7 +37,7 @@
 #pragma ON_PRAGMA_WARNING_BEFORE_DIRTY_INCLUDE
 #include <Shlobj.h>
 #pragma ON_PRAGMA_WARNING_AFTER_DIRTY_INCLUDE
-#if defined(_M_X64) && defined(WIN32) && defined(WIN64)
+#if (defined(_M_X64) || defined(_M_ARM64)) && defined(WIN32) && defined(WIN64)
 // Shlwapi.h, Shlobj.h and perhaps others, unconditionally define WIN32
 #undef WIN32
 #endif
@@ -3302,13 +3302,13 @@ void ON_ContentHash::Dump(
 
     const ON_wString content_time
       = ( m_content_time <= 0 )
-      ? L"unknown"
+      ? static_cast<ON_wString>(L"unknown")
       : SecondsSinceJanOne1970UTCToString(m_content_time);
     text_log.Print(L"Content last modified time = %ls\n",static_cast<const wchar_t*>(content_time));
 
     const ON_wString hash_time
       = ( m_hash_time <= 0 )
-      ? L"unknown"
+      ? static_cast<ON_wString>(L"unknown")
       : SecondsSinceJanOne1970UTCToString(m_hash_time);
     text_log.Print(L"Content hash calculated time = %ls\n",static_cast<const wchar_t*>(content_time));
 
diff --git a/opennurbs_gl.cpp b/opennurbs_gl.cpp
index c47e625a..a649ddec 100644
--- a/opennurbs_gl.cpp
+++ b/opennurbs_gl.cpp
@@ -600,7 +600,7 @@ void ON_GL( const ON_Material* pMat )
     ON_GL( pMat->Diffuse(), alpha, diffuse );
     ON_GL( pMat->Specular(), alpha, specular );
     ON_GL( pMat->Emission(), alpha, emission );
-    GLint shine = (GLint)(128.0*(pMat->Shine() / ON_Material::MaxShine()));
+    GLint shine = (GLint)(128.0*(pMat->Shine() / ON_Material::MaxShine));
     if ( shine == 0 ) {
       specular[0]=specular[1]=specular[2]=(GLfloat)0.0;
     }
diff --git a/opennurbs_locale.cpp b/opennurbs_locale.cpp
index 45c46a5b..92e50e19 100644
--- a/opennurbs_locale.cpp
+++ b/opennurbs_locale.cpp
@@ -1343,7 +1343,7 @@ class ON_CRT_LOCALE
 
   static bool Validate_sprintf_l()
   {
-#if defined(ON_COMPILER_CLANG) || defined(ON_COMPILER_GNU)
+#if (defined(ON_COMPILER_CLANG) || defined(ON_COMPILER_GNU)) && !defined(ON_RUNTIME_WIN)
 #if defined(ON_RUNTIME_ANDROID) || defined(ON_RUNTIME_LINUX)
     // Test formatted printing
     char buffer[64] = { 0 };
@@ -1368,7 +1368,7 @@ class ON_CRT_LOCALE
 
   static bool Validate_sprintf_s_l()
   {
-#if defined(ON_COMPILER_CLANG) || defined(ON_COMPILER_GNU)
+#if (defined(ON_COMPILER_CLANG) || defined(ON_COMPILER_GNU)) && !defined(ON_RUNTIME_WIN)
 #if defined(ON_RUNTIME_ANDROID) || defined(ON_RUNTIME_LINUX)
     // Test formatted printing
     char buffer[64] = { 0 };
@@ -1422,7 +1422,7 @@ class ON_CRT_LOCALE
 
   static bool Validate_sscanf_l()
   {
-#if defined(ON_COMPILER_CLANG) || defined(ON_COMPILER_GNU)
+#if (defined(ON_COMPILER_CLANG) || defined(ON_COMPILER_GNU)) && !defined(ON_RUNTIME_WIN)
 #if defined(ON_RUNTIME_ANDROID) || defined(ON_RUNTIME_LINUX)
     // Test formatted scanning
     double a = ON_UNSET_VALUE;
@@ -1447,7 +1447,7 @@ class ON_CRT_LOCALE
 
   static bool Validate_sscanf_s_l()
   {
-#if defined(ON_COMPILER_CLANG) || defined(ON_COMPILER_GNU)
+#if (defined(ON_COMPILER_CLANG) || defined(ON_COMPILER_GNU)) && !defined(ON_RUNTIME_WIN)
 #if defined(ON_RUNTIME_ANDROID) || defined(ON_RUNTIME_LINUX)
     // Test formatted scanning
     double a = ON_UNSET_VALUE;
diff --git a/opennurbs_lock.h b/opennurbs_lock.h
index a428c857..4902d938 100644
--- a/opennurbs_lock.h
+++ b/opennurbs_lock.h
@@ -112,8 +112,8 @@ class ON_CLASS ON_Lock
   //         needs to have dll-interface to be used by clients of class 'ON_Lock'
   // m_lock_value is private and all code that manages m_lock_value is explicitly implemented in the DLL.
 private:
-#if defined(ON_COMPILER_CLANG)
-    std::atomic<int> m_lock_value;
+#if defined(ON_CLANG_CONSTRUCTOR_BUG_INIT)
+  std::atomic<int> m_lock_value;
 #else
   std::atomic<int> m_lock_value = ON_Lock::UnlockedValue;
 #endif
diff --git a/opennurbs_mesh.cpp b/opennurbs_mesh.cpp
index c7c78cb2..ca06b819 100644
--- a/opennurbs_mesh.cpp
+++ b/opennurbs_mesh.cpp
@@ -14831,7 +14831,9 @@ bool ON_MeshCache::Transform(
     ON_Mesh* mesh = item->m_mesh_sp.get();
     if (nullptr == mesh || mesh->IsEmpty())
       continue;
-    if (false == item->m_mesh_sp.unique())
+    // NOTE: use_count() == 1 is an approximation in multi-threaded environments
+    // https:// en.cppreference.com/w/cpp/memory/shared_ptr/unique
+    if (false == item->m_mesh_sp.use_count() == 1)
     {
       // make a copy and transform the copy
       std::shared_ptr<ON_Mesh>(new ON_Mesh(*mesh)).swap(item->m_mesh_sp);
diff --git a/opennurbs_object_history.cpp b/opennurbs_object_history.cpp
index a3d06de4..fd77eaee 100644
--- a/opennurbs_object_history.cpp
+++ b/opennurbs_object_history.cpp
@@ -31,7 +31,7 @@ class ON_Value
   // The VALUE_TYPE enum values must never be changed
   // because the values are used to determine the parameter
   // type during file reading.  Additions can be made.
-  enum VALUE_TYPE
+  enum VALUE_TYPE: unsigned int
   {
     no_value_type         =  0,
 
diff --git a/opennurbs_precompiledheader.cpp b/opennurbs_precompiledheader.cpp
index 38b46206..2aa370ec 100644
--- a/opennurbs_precompiledheader.cpp
+++ b/opennurbs_precompiledheader.cpp
@@ -32,9 +32,9 @@
 #error Incorrect _M_... setting for x64 build
 #endif
 
-#if !defined(_M_X64)
+#if !defined(_M_X64) && !defined(_M_ARM64)
 // This should be automatically defined by the compiler
-#error _M_X64 should be defined for x64 builds
+#error _M_X64 or _M_ARM64 should be defined for x64 or ARM64 builds
 #endif
 
 // All opennurbs code uses the "offical" _M_X64. Unfortunately, 
@@ -43,9 +43,9 @@
 // _M_X64 and _M_AMD64 for the WIN64 platform.  If it doesn't,
 // then we have a serious problem because some system header
 // files will not be correctly preprocessed.
-#if !defined(_M_AMD64)
+#if !defined(_M_AMD64) && !defined(_M_ARM64)
 // This should be automatically defined by the compiler
-#error _M_AMD64 should be defined for x64 builds
+#error _M_AMD64 or _M_ARM64 should be defined for x64 or ARM64 builds
 #endif
 
 #endif
@@ -57,7 +57,7 @@
 #error Microsoft defines _WIN32 for all Windows builds
 #endif
 
-#if defined(_M_IA64) || defined(_M_X64) || defined(_M_AMD64)
+#if defined(_M_IA64) || defined(_M_X64) || defined(_M_AMD64) || defined(_M_ARM64)
 #error Incorrect _M_... setting for 32 bit Windows build.
 #endif
 
@@ -108,9 +108,9 @@
 #error Incorrect _M_... setting for x64 build
 #endif
 
-#if !defined(_M_X64)
+#if !defined(_M_X64) && !defined(_M_ARM64)
 // This should be automatically defined by the compiler
-#error _M_X64 should be defined for x64 builds
+#error _M_X64 or _M_ARM64 should be defined for x64 or ARM64 builds
 #endif
 
 // All opennurbs code uses the "offical" _M_X64. Unfortunately, 
@@ -119,9 +119,9 @@
 // _M_X64 and _M_AMD64 for the WIN64 platform.  If it doesn't,
 // then we have a serious problem because some system header
 // files will not be correctly preprocessed.
-#if !defined(_M_AMD64)
+#if !defined(_M_AMD64) && !defined(_M_ARM64)
 // This should be automatically defined by the compiler
-#error _M_AMD64 should be defined for x64 builds
+#error _M_AMD64 or _M_ARM64 should be defined for x64 or ARM6 builds
 #endif
 
 #endif
@@ -133,7 +133,7 @@
 #error Microsoft defines _WIN32 for all Windows builds
 #endif
 
-#if defined(_M_IA64) || defined(_M_X64) || defined(_M_AMD64)
+#if defined(_M_IA64) || defined(_M_X64) || defined(_M_AMD64) || defined(_M_ARM64)
 #error Incorrect _M_... setting for 32 bit Windows build.
 #endif
 
diff --git a/opennurbs_statics.cpp b/opennurbs_statics.cpp
index bc23eb8f..075a3d9d 100644
--- a/opennurbs_statics.cpp
+++ b/opennurbs_statics.cpp
@@ -515,7 +515,7 @@ static ON_SHA1_Hash ON_SHA1_Hash_EmptyContentHash()
 const ON_SHA1_Hash ON_SHA1_Hash::EmptyContentHash = ON_SHA1_Hash_EmptyContentHash();
 const ON_SHA1_Hash ON_SHA1_Hash::ZeroDigest ON_CLANG_CONSTRUCTOR_BUG_INIT(ON_SHA1_Hash);
 
-const ONX_ModelTest ONX_ModelTest::Unset ON_CLANG_CONSTRUCTOR_BUG_INIT(ONX_ModelTest);
+const ONX_ModelTest ONX_ModelTest::Unset = ONX_ModelTest();
 
 // Works with Microsoft's CL, fails for Apple's CLang
 ////   const struct ON_UnicodeErrorParameters ON_UnicodeErrorParameters::MaskErrors   = { 0, 0xFFFFFFFF, ON_UnicodeCodePoint::ON_ReplacementCharacter };
@@ -744,7 +744,7 @@ const ON_AngleUnitName ON_AngleUnitName::None ON_CLANG_CONSTRUCTOR_BUG_INIT(ON_A
 const ON_LengthValue ON_LengthValue::Unset ON_CLANG_CONSTRUCTOR_BUG_INIT(ON_LengthValue);
 const ON_LengthValue ON_LengthValue::Zero = ON_LengthValue::Create(0.0, ON::LengthUnitSystem::None, 0, ON_LengthValue::StringFormat::CleanDecimal);
 
-const ON_AngleValue ON_AngleValue::Unset ON_CLANG_CONSTRUCTOR_BUG_INIT(ON_AngleValue);
+const ON_AngleValue ON_AngleValue::Unset = ON_AngleValue();
 const ON_AngleValue ON_AngleValue::Zero = ON_AngleValue::Create(0.0, ON::AngleUnitSystem::None, 0, ON_AngleValue::StringFormat::CleanDecimal );
 
 const ON_ScaleValue ON_ScaleValue::Unset ON_CLANG_CONSTRUCTOR_BUG_INIT(ON_ScaleValue);
diff --git a/opennurbs_string_format.cpp b/opennurbs_string_format.cpp
index 304b351e..8dd6e158 100644
--- a/opennurbs_string_format.cpp
+++ b/opennurbs_string_format.cpp
@@ -803,7 +803,7 @@ int ON_String::FormatVargsIntoBuffer(
   if (0 == buffer || buffer_capacity <= 0)
     return -1;
   buffer[0] = 0;
-#if defined(ON_COMPILER_CLANG) || defined(ON_COMPILER_GNU)
+#if (defined(ON_COMPILER_CLANG) || defined(ON_COMPILER_GNU)) && !defined(ON_RUNTIME_WIN)
   // CLang modifies args so a copy is required
   va_list args_copy;
   va_copy (args_copy, args);
@@ -854,7 +854,7 @@ int ON_String::FormatVargsOutputCount(
   if ( nullptr == format || 0 == format[0] )
     return 0;
 
-#if defined(ON_COMPILER_CLANG) || defined(ON_COMPILER_GNU)
+#if (defined(ON_COMPILER_CLANG) || defined(ON_COMPILER_GNU)) && !defined(ON_RUNTIME_WIN)
   // CLang modifies args so a copy is required
   va_list args_copy;
   va_copy (args_copy, args);
diff --git a/opennurbs_string_scan.cpp b/opennurbs_string_scan.cpp
index 34df9069..efe90f93 100644
--- a/opennurbs_string_scan.cpp
+++ b/opennurbs_string_scan.cpp
@@ -85,7 +85,7 @@ int ON_String::ScanBufferVargs(
   va_list args
   )
 {
-#if defined(ON_COMPILER_CLANG) || defined(ON_RUNTIME_LINUX)
+#if (defined(ON_COMPILER_CLANG) || defined(ON_RUNTIME_LINUX)) && !defined(ON_RUNTIME_WIN)
 #if defined(ON_RUNTIME_ANDROID) || defined(ON_RUNTIME_LINUX)
   if (nullptr == buffer || nullptr == format)
     return -1;
@@ -398,7 +398,7 @@ const char* ON_String::ToNumber(
   local_buffer[local_buffer_count++] = 0;
 
   double x = value_on_failure;
-#if defined(ON_COMPILER_CLANG) || defined(ON_RUNTIME_LINUX)
+#if (defined(ON_COMPILER_CLANG) || defined(ON_RUNTIME_LINUX)) && !defined(ON_RUNTIME_WIN)
 #if defined(ON_RUNTIME_ANDROID) || defined(ON_RUNTIME_LINUX)
   if (1 == sscanf(local_buffer, "%lg", &x))
   {
@@ -660,7 +660,7 @@ const wchar_t* ON_wString::ToNumber(
   local_buffer[local_buffer_count++] = 0;
 
   double x = value_on_failure;
-#if defined(ON_COMPILER_CLANG) || defined(ON_RUNTIME_LINUX)
+#if (defined(ON_COMPILER_CLANG) || defined(ON_RUNTIME_LINUX)) && !defined(ON_RUNTIME_WIN)
 #if defined(ON_RUNTIME_ANDROID) || defined(ON_RUNTIME_LINUX)
   if (1 == sscanf(local_buffer, "%lg", &x))
   {
diff --git a/opennurbs_system.h b/opennurbs_system.h
index 504fea2f..4aa458fd 100644
--- a/opennurbs_system.h
+++ b/opennurbs_system.h
@@ -383,7 +383,7 @@ typedef ON__UINT32 wchar_t;
 */
 
 
-#if defined(_M_X64) && defined(WIN32) && defined(WIN64)
+#if (defined(_M_X64) || defined(_M_ARM64)) && defined(WIN32) && defined(WIN64)
 // 23 August 2007 Dale Lear
 
 #if defined(_INC_WINDOWS)
@@ -406,7 +406,7 @@ typedef ON__UINT32 wchar_t;
 #pragma ON_PRAGMA_WARNING_AFTER_DIRTY_INCLUDE
 #endif
 
-#if defined(_M_X64) && defined(WIN32) && defined(WIN64)
+#if (defined(_M_X64) || defined(_M_ARM64)) && defined(WIN32) && defined(WIN64)
 // 23 August 2007 Dale Lear
 //   windows.h unconditionally defines WIN32  This is a bug
 //   and the hope is this simple undef will let us continue.
@@ -542,6 +542,8 @@ typedef ON__UINT32 wchar_t;
 #pragma ON_PRAGMA_WARNING_BEFORE_DIRTY_INCLUDE
 #if defined(ON_RUNTIME_ANDROID) || defined(ON_RUNTIME_LINUX)
 #include "android_uuid/uuid.h"
+#elif defined(ON_RUNTIME_WIN)
+#include <Rpc.h>
 #else
 #include <uuid/uuid.h>
 #endif
diff --git a/opennurbs_system_runtime.h b/opennurbs_system_runtime.h
index 683b73ef..f2e4ae56 100644
--- a/opennurbs_system_runtime.h
+++ b/opennurbs_system_runtime.h
@@ -137,7 +137,7 @@
 #define ON_RUNTIME_WIN_WINOS
 #endif
 
-#if defined(_M_X64) || defined(_WIN64)
+#if defined(_M_X64) || defined(_M_ARM64) || defined(_WIN64)
 #define ON_64BIT_RUNTIME
 #elif defined(_M_X86) || defined(_WIN32)
 #define ON_32BIT_RUNTIME
@@ -146,7 +146,7 @@
 #endif
 
 #if !defined(ON_LITTLE_ENDIAN)
-#if (defined(_M_X64) || defined(_M_IX86) || defined (__i386__) || defined( __x86_64__ ))
+#if (defined(_M_X64) || defined(_M_ARM64) || defined(_M_IX86) || defined(__i386__) || defined(__x86_64__))
 #define ON_LITTLE_ENDIAN
 #endif
 #endif
diff --git a/opennurbs_version_number.cpp b/opennurbs_version_number.cpp
index 7ca9e81c..65379a76 100644
--- a/opennurbs_version_number.cpp
+++ b/opennurbs_version_number.cpp
@@ -375,7 +375,7 @@ const ON_String ON_VersionNumberToString(
     str_version =
       (0 != version_number)
       ? ON_String::FormatToString("0x%08X", version_number)
-      : "0";
+      : static_cast<ON_String>("0");
   }
 
   return str_version;