diff --git a/build/cmake/README.md b/build/cmake/README.md
index 708b78a434..82e13a28c6 100644
--- a/build/cmake/README.md
+++ b/build/cmake/README.md
@@ -28,9 +28,9 @@ Files
     * Every function should contain a short description of it's parameters as
       a comment before the function/macro
 * install.cmake
-    * Handles defintions for the `install` and `uninstall` target
+    * Handles definitions for the `install` and `uninstall` target
 * init.cmake
-    * Intializes various variables used during the build process and for
+    * Initializes various variables used during the build process and for
       generation of setup.h and configuration files
 * main.cmake
     * Includes all other cmake files
@@ -60,7 +60,7 @@ _.cmake_ files.
     * Defines build targets for demos via `wx_add_demo()`
 * lib
     * Defines build targets for all libraries and bundle third party libraries
-    * Each library is contained in a seperate directory and uses
+    * Each library is contained in a separate directory and uses
       `wx_add_library()` to define the library target
     * Bundled third party library without upstream CMake support are defined in
       a _.cmake_ file using `wx_add_builtin_library()` to define static library
@@ -70,8 +70,8 @@ _.cmake_ files.
     * Includes the [cotire module][4] used to for precompiled header generation
 * samples
     * Defines build targets for all samples via `wx_add_sample()`
-    * Defintions for trivial samples are included in _CMakeLists.txt_ more
-      complex samples might have a seperate .cmake file
+    * Definitions for trivial samples are included in _CMakeLists.txt_ more
+      complex samples might have a separate .cmake file
 * tests
     * Defines build targets for all tests
 * utils
diff --git a/build/cmake/functions.cmake b/build/cmake/functions.cmake
index 84fe6e3f7d..8d4dc94511 100644
--- a/build/cmake/functions.cmake
+++ b/build/cmake/functions.cmake
@@ -8,7 +8,7 @@
 #############################################################################
 
 include(CMakeDependentOption)
-include(CMakeParseArguments)           # For compatiblity with CMake < 3.4
+include(CMakeParseArguments)           # For compatibility with CMake < 3.4
 include(ExternalProject)
 if(CMAKE_GENERATOR STREQUAL "Xcode")
     # wxWidgets does not use the unity features of cotire so we can
@@ -314,25 +314,30 @@ macro(wx_add_library name)
     endif()
 endmacro()
 
-# Enable cotire for target if precompiled headers are enabled
+# Enable cotire for target, use optional second argument for prec. header
 macro(wx_target_enable_precomp target_name)
-    if(wxBUILD_PRECOMP)
-        if(APPLE AND ${target_name} STREQUAL "wxscintilla")
-            # TODO: workaround/fix cotire issue with wxscintilla when using Xcode
-        else()
-            set_target_properties(${target_name} PROPERTIES COTIRE_ADD_UNITY_BUILD FALSE)
-            cotire(${target_name})
-        endif()
+    target_compile_definitions(${target_name} PRIVATE WX_PRECOMP)
+    if(NOT ${ARGV1} STREQUAL "")
+        set_target_properties(${target_name} PROPERTIES
+            COTIRE_CXX_PREFIX_HEADER_INIT ${ARGV1})
     endif()
+    set_target_properties(${target_name} PROPERTIES COTIRE_ADD_UNITY_BUILD FALSE)
+    cotire(${target_name})
 endmacro()
 
 # Enable precompiled headers for tests
 macro(wx_test_enable_precomp target_name)
     if(wxBUILD_PRECOMP)
-        target_compile_definitions(${target_name} PRIVATE WX_PRECOMP)
-        set_target_properties(${target_name} PROPERTIES
-            COTIRE_CXX_PREFIX_HEADER_INIT "${wxSOURCE_DIR}/tests/testprec.h")
-        wx_target_enable_precomp(${target_name})
+        wx_target_enable_precomp(${target_name} "${wxSOURCE_DIR}/tests/testprec.h")
+    elseif(MSVC)
+        target_compile_definitions(${target_name} PRIVATE NOPCH)
+    endif()
+endmacro()
+
+# Enable precompiled headers for samples
+macro(wx_sample_enable_precomp target_name)
+    if(wxBUILD_PRECOMP)
+        wx_target_enable_precomp(${target_name} "${wxSOURCE_DIR}/include/wx/wxprec.h")
     elseif(MSVC)
         target_compile_definitions(${target_name} PRIVATE NOPCH)
     endif()
@@ -343,10 +348,7 @@ macro(wx_finalize_lib target_name)
     set(wxLIB_TARGETS ${wxLIB_TARGETS} PARENT_SCOPE)
     if(wxBUILD_PRECOMP)
         if(TARGET ${target_name})
-            target_compile_definitions(${target_name} PRIVATE WX_PRECOMP)
-            set_target_properties(${target_name} PROPERTIES
-                COTIRE_CXX_PREFIX_HEADER_INIT "${wxSOURCE_DIR}/include/wx/wxprec.h")
-            wx_target_enable_precomp(${target_name})
+        wx_target_enable_precomp(${target_name} "${wxSOURCE_DIR}/include/wx/wxprec.h")
         endif()
     elseif(MSVC)
         wx_lib_compile_definitions(${target_name} PRIVATE NOPCH)
@@ -544,7 +546,7 @@ endfunction()
 # IMPORTANT does not require wxBUILD_SAMPLES=ALL
 # RES followed by WIN32 .rc files
 #
-# Additinally the following variables may be set before calling wx_add_sample:
+# Additionally the following variables may be set before calling wx_add_sample:
 # wxSAMPLE_SUBDIR subdirectory in the samples/ folder to use as base
 # wxSAMPLE_FOLDER IDE sub folder to be used for the samples
 function(wx_add_sample name)
@@ -629,8 +631,6 @@ function(wx_add_sample name)
     if(SAMPLE_DEFINITIONS)
         target_compile_definitions(${target_name} PRIVATE ${SAMPLE_DEFINITIONS})
     endif()
-    # Disable precompile headers for samples
-    target_compile_definitions(${target_name} PRIVATE NOPCH)
     if(SAMPLE_DATA)
         # TODO: handle data files differently for OS X bundles
         # Copy data files to output directory
@@ -667,6 +667,7 @@ function(wx_add_sample name)
         wx_string_append(folder "/${SAMPLE_FOLDER}")
     endif()
     wx_set_common_target_properties(${target_name})
+    wx_sample_enable_precomp(${target_name})
     set_target_properties(${target_name} PROPERTIES
         FOLDER ${folder}
         )
diff --git a/build/cmake/init.cmake b/build/cmake/init.cmake
index fac86758b6..4c93866c8f 100644
--- a/build/cmake/init.cmake
+++ b/build/cmake/init.cmake
@@ -51,10 +51,12 @@ set(wxARCH_SUFFIX)
 
 # TODO: include compiler version in wxCOMPILER_PREFIX ?
 if(WIN32)
-    if(MSVC)
+    if("${CMAKE_CXX_COMPILER_ID}" STREQUAL "MSVC")
         set(wxCOMPILER_PREFIX "vc")
-    elseif(CMAKE_COMPILER_IS_GNUCXX)
+    elseif("${CMAKE_CXX_COMPILER_ID}" STREQUAL "GNU")
         set(wxCOMPILER_PREFIX "gcc")
+    elseif("${CMAKE_CXX_COMPILER_ID}" STREQUAL "Clang")
+        set(wxCOMPILER_PREFIX "clang")
     else()
         message(FATAL_ERROR "Unknown WIN32 compiler type")
     endif()
@@ -74,7 +76,7 @@ if(MSVC OR MINGW)
     endif()
 
     if(MSVC)
-        # Include generator expression to supress default Debug/Release pair
+        # Include generator expression to suppress default Debug/Release pair
         set(wxPLATFORM_LIB_DIR "$<1:/>${wxCOMPILER_PREFIX}${wxARCH_SUFFIX}_${lib_suffix}")
     else()
         set(wxPLATFORM_LIB_DIR "/${wxCOMPILER_PREFIX}${wxARCH_SUFFIX}_${lib_suffix}")
diff --git a/build/cmake/lib/stc/CMakeLists.txt b/build/cmake/lib/stc/CMakeLists.txt
index 55e3eafdf6..27af21bb79 100644
--- a/build/cmake/lib/stc/CMakeLists.txt
+++ b/build/cmake/lib/stc/CMakeLists.txt
@@ -164,7 +164,17 @@ target_compile_definitions(wxscintilla PUBLIC
     NO_CXX11_REGEX
     __WX__
 )
-wx_target_enable_precomp(wxscintilla)
+
+if(wxBUILD_PRECOMP)
+    # The auto-generated header causes undefined members and identifiers in the
+    # standard c++ headers when using clang on macOS or Windows.
+    # Do not disable precompiled headers entirely but use the main Scintilla
+    # header as prefix header so there is at least a small speedup.
+    if ("${CMAKE_CXX_COMPILER_ID}" STREQUAL "Clang" AND (APPLE OR WIN32))
+        set(wxSCINTILLA_PREC_HEADER "${wxSOURCE_DIR}/src/stc/scintilla/include/Scintilla.h")
+    endif()
+    wx_target_enable_precomp(wxscintilla ${wxSCINTILLA_PREC_HEADER})
+endif()
 
 wx_add_library(stc ${STC_FILES})
 wx_lib_include_directories(stc PRIVATE
diff --git a/build/cmake/options.cmake b/build/cmake/options.cmake
index 4a3d18a533..48b2ddf70a 100644
--- a/build/cmake/options.cmake
+++ b/build/cmake/options.cmake
@@ -403,7 +403,6 @@ if(WIN32)
         set(wxUSE_WINRT_DEFAULT OFF)
     endif()
     wx_option(wxUSE_WINRT "enable WinRT support" ${wxUSE_WINRT_DEFAULT})
-    
 endif()
 
 # this one is not really MSW-specific but it exists mainly to be turned off
diff --git a/build/cmake/samples/CMakeLists.txt b/build/cmake/samples/CMakeLists.txt
index b59b698f63..27822b3b5f 100644
--- a/build/cmake/samples/CMakeLists.txt
+++ b/build/cmake/samples/CMakeLists.txt
@@ -199,7 +199,7 @@ wx_list_add_prefix(WIDGETS_RC_FILES icons/
     slider.xpm spinbtn.xpm statbmp.xpm statbox.xpm
     stattext.xpm text.xpm timepick.xpm toggle.xpm
     )
-wx_add_sample(widgets IMPORTANT ${SAMPLE_WIDGETS_SRC} 
+wx_add_sample(widgets IMPORTANT ${SAMPLE_WIDGETS_SRC}
     DATA ${WIDGETS_RC_FILES} textctrl.cpp
     LIBRARIES adv
     )
@@ -258,7 +258,7 @@ if(WIN32)
     if(MSVC)
         wx_add_sample(flash)
     endif()
-    #TODO: renable when sample is fixed
+    #TODO: reenable when sample is fixed
     #wx_add_sample(mfc mfctest.cpp mfctest.h resource.h stdafx.h RES mfctest.rc)
     wx_add_sample(nativdlg nativdlg.cpp nativdlg.h resource.h RES nativdlg.rc)
     wx_add_sample(oleauto DEPENDS wxUSE_OLE)
diff --git a/build/cmake/setup.cmake b/build/cmake/setup.cmake
index 700d41e0f5..46092b0797 100644
--- a/build/cmake/setup.cmake
+++ b/build/cmake/setup.cmake
@@ -310,7 +310,7 @@ if(NOT WIN32)
             statfs(\"/\", &fs);"
             HAVE_STATFS_DECL)
     else()
-        # TODO: implment statvfs checks
+        # TODO: implement statvfs checks
         if(HAVE_STATVFS)
             set(WX_STATFS_T statvfs_t)
         endif()
diff --git a/samples/taskbarbutton/taskbarbutton.cpp b/samples/taskbarbutton/taskbarbutton.cpp
index 16241b5a93..f386832cf9 100644
--- a/samples/taskbarbutton/taskbarbutton.cpp
+++ b/samples/taskbarbutton/taskbarbutton.cpp
@@ -15,10 +15,10 @@
 
 #ifndef WX_PRECOMP
     #include "wx/progdlg.h"
-    #include "wx/stdpaths.h"
     #include "wx/wx.h"
 #endif
 
+#include "wx/stdpaths.h"
 #include "wx/taskbarbutton.h"
 
 enum
diff --git a/src/msw/dirdlg.cpp b/src/msw/dirdlg.cpp
index 84557d7c95..b0b9ed84d9 100644
--- a/src/msw/dirdlg.cpp
+++ b/src/msw/dirdlg.cpp
@@ -73,12 +73,15 @@ struct IShellItem : public IUnknown
 
 #endif // #ifndef __IShellItem_INTERFACE_DEFINED__
 
+#if defined(__VISUALC__) || !defined(__IShellItem_INTERFACE_DEFINED__)
 // Define this GUID in any case, even when __IShellItem_INTERFACE_DEFINED__ is
 // defined in the headers we might still not have it in the actual uuid.lib,
-// this happens with at least VC7 used with its original (i.e. not updated) SDK
-// and there is no harm in defining the GUID unconditionally.
+// this happens with at least VC7 used with its original (i.e. not updated) SDK.
+// clang complains about multiple definitions, so only define it unconditionally
+// when using a Visual C compiler.
 DEFINE_GUID(IID_IShellItem,
     0x43826D1E, 0xE718, 0x42EE, 0xBC, 0x55, 0xA1, 0xE2, 0x61, 0xC3, 0x7B, 0xFE);
+#endif
 
 struct IShellItemFilter;
 struct IFileDialogEvents;
diff --git a/src/msw/mediactrl_am.cpp b/src/msw/mediactrl_am.cpp
index 1b8c9e6bd7..5379eda8af 100644
--- a/src/msw/mediactrl_am.cpp
+++ b/src/msw/mediactrl_am.cpp
@@ -1530,7 +1530,9 @@ void wxAMMediaBackend::Move(int WXUNUSED(x), int WXUNUSED(y),
 //---------------------------------------------------------------------------
 void wxAMMediaEvtHandler::OnActiveX(wxActiveXEvent& event)
 {
-    switch(event.GetDispatchId())
+    // cast to unsigned long to fix narrowing error with case 0xfffffd9f
+    // when using clang
+    switch (static_cast<unsigned long>(event.GetDispatchId()))
     {
     case 0x00000001: // statechange in IActiveMovie
     case 0x00000bc4: // playstatechange in IMediaPlayer