[CMAKE] Elimitate the use of GCC and CLANG variables

CMakeLists.txt

@@ -76,8 +76,7 @@ add_definitions(
 
 # There doesn't seem to be a standard for __FILE__ being relative or absolute, so detect it at runtime.
 file(RELATIVE_PATH _PATH_PREFIX ${REACTOS_BINARY_DIR} ${REACTOS_SOURCE_DIR})
-if (GCC AND ((CMAKE_C_COMPILER_ID STREQUAL "GNU") AND (CMAKE_C_COMPILER_VERSION VERSION_GREATER_EQUAL "8.0.0")
-    OR ((CMAKE_C_COMPILER_ID STREQUAL "Clang") AND (CMAKE_C_COMPILER_VERSION VERSION_GREATER_EQUAL "10.0.0"))))
+if (NOT MSVC AND (CMAKE_C_COMPILER_ID STREQUAL "GNU" OR CMAKE_C_COMPILER_ID STREQUAL "Clang"))
     # Thankfully, GCC has this
     add_compile_options(-ffile-prefix-map=${REACTOS_SOURCE_DIR}=)
     add_compile_options(-ffile-prefix-map=${_PATH_PREFIX}=)
@@ -229,7 +228,7 @@ Enable this if the module uses typeid or dynamic_cast. You will probably need to
         message(WARNING "-- Disabling precompiled headers support (ccache).")
         option(PCH "Whether to use precompiled headers" OFF)
         set_property(GLOBAL PROPERTY RULE_LAUNCH_COMPILE ccache)
-    elseif(GCC)
+    elseif(CMAKE_C_COMPILER_ID STREQUAL "GNU")
         message(WARNING "-- Disabling precompiled headers on GCC by default CORE-17108.")
         option(PCH "Whether to use precompiled headers" OFF)
     else()

base/services/nfsd/CMakeLists.txt

@@ -48,7 +48,7 @@ list(APPEND SOURCE
 
 add_executable(nfsd ${SOURCE} nfsd.rc)
 
-if(MSVC AND (NOT USE_CLANG_CL))
+if(CMAKE_C_COMPILER_ID STREQUAL "MSVC")
     # Disable warning C4477 (printf format warnings)
     target_compile_options(nfsd PRIVATE /wd4477)
 else()

boot/rtl/blrtl.cmake

@@ -7,7 +7,7 @@ add_definitions(
 set(NTOS_RTL_SOURCE_DIR "${REACTOS_SOURCE_DIR}/sdk/lib/rtl")
 include_directories(${NTOS_RTL_SOURCE_DIR})
 
-if (GCC)
+if (CMAKE_C_COMPILER_ID STREQUAL "GNU" OR CMAKE_C_COMPILER_ID STREQUAL "Clang")
     # Enable this again. CORE-17637
     add_compile_options(-Wunused-result)
 endif()

dll/3rdparty/libxslt/CMakeLists.txt

@@ -43,7 +43,7 @@ if(MSVC)
     add_importlibs(libxslt ntdll)
 endif()
 
-if(GCC OR CLANG)
+if(NOT MSVC)
     target_compile_options(libxslt PRIVATE -Wno-misleading-indentation -Wno-pointer-sign -Wno-unused-function)
 endif()
 

dll/3rdparty/mbedtls/CMakeLists.txt

@@ -102,6 +102,8 @@ add_cd_file(TARGET mbedtls DESTINATION reactos/system32 FOR all)
 
 if(NOT MSVC)
     target_compile_options(mbedtls PRIVATE -Wno-pointer-sign -Wno-unused-function)
-elseif(USE_CLANG_CL)
+endif()
+
+if(CMAKE_C_COMPILER_ID STREQUAL "Clang")
     target_compile_options(mbedtls PRIVATE -Wno-tautological-constant-compare)
 endif()

dll/opengl/glu32/CMakeLists.txt

@@ -120,19 +120,19 @@ target_link_libraries(glu32 cpprt)
 
 set_module_type(glu32 win32dll)
 
-if(NOT MSVC)
-    target_compile_options(glu32 PRIVATE -Wno-write-strings)
-elseif(USE_CLANG_CL)
-    target_compile_options(glu32 PRIVATE -Wno-self-assign -Wno-unused-function -Wno-microsoft-include)
-    target_compile_options(glu32 PRIVATE -Wno-deprecated-register -Wno-tautological-undefined-compare)
-endif()
-
 if(CMAKE_C_COMPILER_ID STREQUAL "GNU")
+    target_compile_options(glu32 PRIVATE -Wno-write-strings)
     target_compile_options(glu32 PRIVATE -Wno-unused-but-set-variable)
     # Prevent a warning when comparing 'this' against 0
     set_source_files_properties(src/libnurbs/internals/arc.cc PROPERTIES COMPILE_FLAGS "-Wno-nonnull-compare")
 endif()
 
+if(CMAKE_C_COMPILER_ID STREQUAL "Clang")
+    target_compile_options(glu32 PRIVATE -Wno-write-strings)
+    target_compile_options(glu32 PRIVATE -Wno-self-assign -Wno-unused-function -Wno-microsoft-include)
+    target_compile_options(glu32 PRIVATE -Wno-deprecated-register -Wno-tautological-undefined-compare)
+endif()
+
 add_importlibs(glu32 opengl32 gdi32 msvcrt kernel32 ntdll)
 add_pch(glu32 precomp.h "${PCH_SKIP_SOURCE}")
 add_cd_file(TARGET glu32 DESTINATION reactos/system32 FOR all)

drivers/filesystems/ext2/CMakeLists.txt

@@ -88,26 +88,21 @@ list(APPEND SOURCE
 
 add_library(ext2fs MODULE ${SOURCE} ext2fs.rc)
 
-if(MSVC)
-    if (NOT CLANG)
-        # Disable warning C4101: 'i': unreferenced local variable
-        # Disable warning C4189: 'sbi': local variable is initialized but not referenced
-        # Disable warning C4267: '=': conversion from 'size_t' to 'USHORT', possible loss of data
-        target_compile_options(ext2fs PRIVATE /wd4101 /wd4189 /wd4267)
-    endif()
-else()
-    target_compile_options(ext2fs PRIVATE
-        -Wno-pointer-sign -Wno-unused-function
-        -Wno-unused-variable -Wno-missing-braces)
+if(CMAKE_C_COMPILER_ID STREQUAL "MSVC")
+    # Disable warning C4101: 'i': unreferenced local variable
+    # Disable warning C4189: 'sbi': local variable is initialized but not referenced
+    # Disable warning C4267: '=': conversion from 'size_t' to 'USHORT', possible loss of data
+    target_compile_options(ext2fs PRIVATE /wd4101 /wd4189 /wd4267)
 endif()
 
-if(CMAKE_C_COMPILER_ID STREQUAL "GNU")
-    target_compile_options(ext2fs PRIVATE -Wno-unused-but-set-variable)
+if(CMAKE_C_COMPILER_ID STREQUAL "GNU" OR CMAKE_C_COMPILER_ID STREQUAL "Clang")
+    target_compile_options(ext2fs PRIVATE
+        -Wno-pointer-sign -Wno-unused-function -Wno-unused-variable -Wno-missing-braces -Wno-unused-but-set-variable)
 endif()
 
-if(CLANG)
+if(CMAKE_C_COMPILER_ID STREQUAL "Clang")
     target_compile_options(ext2fs PRIVATE
-        -Wno-unused-value -Wno-parentheses-equality
+        -Wno-parentheses-equality
         -Wno-incompatible-pointer-types-discards-qualifiers
         "-Wno-#pragma-messages;-Wno-cast-calling-convention")
 endif()

drivers/filesystems/fastfat_new/CMakeLists.txt

@@ -38,7 +38,7 @@ list(APPEND SOURCE
 add_library(fastfat MODULE ${SOURCE} fastfat.rc)
 set_module_type(fastfat kernelmodedriver)
 target_link_libraries(fastfat ${PSEH_LIB} memcmp)
-if(GDB AND NOT CLANG)
+if(GDB AND NOT CMAKE_C_COMPILER_ID STREQUAL "Clang")
     target_compile_options(fastfat PRIVATE -O0)
 endif()
 add_importlibs(fastfat ntoskrnl hal)

drivers/filesystems/nfs/CMakeLists.txt

@@ -14,12 +14,14 @@ set_module_type(nfs41_driver kernelmodedriver)
 target_link_libraries(nfs41_driver ntoskrnl_vista rdbsslib rxce copysup memcmp ${PSEH_LIB})
 add_importlibs(nfs41_driver ntoskrnl hal)
 
-if(GCC OR CLANG)
+if(CMAKE_C_COMPILER_ID STREQUAL "GNU" OR CMAKE_C_COMPILER_ID STREQUAL "Clang")
     target_compile_options(nfs41_driver PRIVATE "-Wno-switch")
-    if(CLANG)
-        target_compile_options(nfs41_driver PRIVATE "-Wno-unused-value")
-    endif()
 endif()
+
+if(CMAKE_C_COMPILER_ID STREQUAL "Clang")
+    target_compile_options(nfs41_driver PRIVATE "-Wno-unused-value")
+endif()
+
 set_property(TARGET nfs41_driver PROPERTY C_STANDARD 90)
 
 add_cd_file(TARGET nfs41_driver DESTINATION reactos/system32/drivers FOR all)

drivers/filesystems/udfs/CMakeLists.txt

@@ -41,19 +41,17 @@ list(APPEND SOURCE
 
 add_library(udfs MODULE ${SOURCE} udffs.rc)
 
-if(MSVC)
-    if(USE_CLANG_CL)
-        target_compile_options(udfs PRIVATE -Wno-extern-c-compat -Wno-unused-value)
-        target_compile_options(udfs PRIVATE -Wno-tautological-constant-out-of-range-compare)
-        target_compile_options(udfs PRIVATE -Wno-tautological-unsigned-zero-compare -Wno-self-assign)
-        target_compile_options(udfs PRIVATE -Wno-sometimes-uninitialized -Wno-parentheses-equality)
-    endif()
-endif()
-
 if(CMAKE_C_COMPILER_ID STREQUAL "GNU")
     target_compile_options(udfs PRIVATE -Wno-unused-but-set-variable)
 endif()
 
+if(CMAKE_C_COMPILER_ID STREQUAL "Clang")
+    target_compile_options(udfs PRIVATE -Wno-extern-c-compat -Wno-unused-value)
+    target_compile_options(udfs PRIVATE -Wno-tautological-constant-out-of-range-compare)
+    target_compile_options(udfs PRIVATE -Wno-tautological-unsigned-zero-compare -Wno-self-assign)
+    target_compile_options(udfs PRIVATE -Wno-sometimes-uninitialized -Wno-parentheses-equality)
+endif()
+
 set_module_type(udfs kernelmodedriver)
 target_link_libraries(udfs ${PSEH_LIB})
 add_importlibs(udfs ntoskrnl hal)

drivers/storage/class/cdrom/CMakeLists.txt

@@ -20,15 +20,12 @@ list(APPEND SOURCE
 add_library(cdrom MODULE ${SOURCE} cdrom.rc)
 set_module_type(cdrom kernelmodedriver)
 
-if(GCC OR CLANG)
+if(CMAKE_C_COMPILER_ID STREQUAL "GNU" OR CMAKE_C_COMPILER_ID STREQUAL "Clang")
     target_compile_options(cdrom PRIVATE -Wno-format -Wno-unused-variable -Wno-pointer-sign)
-endif()
-
-if(GCC)
     target_compile_options(cdrom PRIVATE -Wno-unknown-pragmas -Wno-incompatible-pointer-types -Wno-switch)
 endif()
 
-if(CLANG)
+if(CMAKE_C_COMPILER_ID STREQUAL "Clang")
     target_compile_options(cdrom PRIVATE -Wno-enum-conversion -Wno-tautological-constant-compare)
 endif()
 

drivers/storage/class/classpnp/CMakeLists.txt

@@ -41,7 +41,7 @@ target_compile_definitions(classpnp PRIVATE
     CLASS_GLOBAL_BUFFERED_DEBUG_PRINT_BUFFER_SIZE=512
     CLASS_GLOBAL_BUFFERED_DEBUG_PRINT_BUFFERS=512)
 
-if(GCC)
+if(NOT MSVC)
     target_compile_options(classpnp PRIVATE -Wno-pointer-to-int-cast -Wno-switch)
 endif()
 

drivers/storage/class/disk/CMakeLists.txt

@@ -16,11 +16,8 @@ target_compile_definitions(disk PUBLIC
     _WIN32_WINNT=0x602
     NTDDI_VERSION=0x06020000) # NTDDI_WIN8
 
-if(USE_CLANG_CL OR (NOT MSVC))
+if(CMAKE_C_COMPILER_ID STREQUAL "GNU" OR CMAKE_C_COMPILER_ID STREQUAL "Clang")
     target_compile_options(disk PRIVATE -Wno-format -Wno-pointer-sign)
-endif()
-
-if(GCC)
     target_compile_options(disk PRIVATE -Wno-pointer-to-int-cast -Wno-switch)
 endif()
 

drivers/storage/ide/uniata/CMakeLists.txt

@@ -21,21 +21,18 @@ list(APPEND SOURCE
 
 add_library(uniata MODULE ${SOURCE} idedma.rc)
 
-if(USE_CLANG_CL OR (NOT MSVC))
-    target_compile_options(uniata PRIVATE "-Wno-narrowing")
-    if(USE_CLANG_CL)
-        target_compile_options(uniata PRIVATE "-Wno-unused-const-variable")
-    endif()
-endif()
-
 if(MSVC)
     # Disable warning C4267: '=': conversion from 'size_t' to 'USHORT', possible loss of data
     # Disable warning C4838: conversion from 'int' to 'ULONG' requires a narrowing conversion
     target_compile_options(uniata PRIVATE /wd4267 /wd4838)
 endif()
 
-if(CMAKE_C_COMPILER_ID STREQUAL "GNU")
-    target_compile_options(uniata PRIVATE -Wno-unused-but-set-variable)
+if(CMAKE_C_COMPILER_ID STREQUAL "GNU" OR CMAKE_C_COMPILER_ID STREQUAL "Clang")
+    target_compile_options(uniata PRIVATE -Wno-narrowing -Wno-unused-but-set-variable)
+endif()
+
+if(CMAKE_C_COMPILER_ID STREQUAL "Clang")
+    target_compile_options(uniata PRIVATE -Wno-unused-const-variable)
 endif()
 
 add_pch(uniata stdafx.h SOURCE)

drivers/wdm/audio/drivers/CMIDriver/CMakeLists.txt

@@ -26,7 +26,7 @@ target_link_libraries(cmipci stdunk libcntpr uuid)
 set_module_type(cmipci wdmdriver UNICODE)
 add_importlibs(cmipci portcls hal ntoskrnl)
 
-if(USE_CLANG_CL OR (NOT MSVC))
+if(CMAKE_C_COMPILER_ID STREQUAL "GNU" OR CMAKE_C_COMPILER_ID STREQUAL "Clang")
     target_compile_options(cmipci PRIVATE -Wno-write-strings -Wno-switch)
 endif()
 

modules/rostests/apitests/compiler/CMakeLists.txt

@@ -1,5 +1,5 @@
 
-if (NOT (GCC AND (ARCH STREQUAL "amd64")))
+if (MSVC OR ARCH STREQUAL "i386")
     #FIXME _setjmp definitions in CRT headers is wrong
     add_subdirectory(ms)
     list(APPEND SOURCE ms_seh.c)
@@ -12,7 +12,7 @@ list(APPEND SOURCE
     testlist.c)
 
 add_executable(compiler_apitest ${SOURCE})
-if (NOT (GCC AND (ARCH STREQUAL "amd64")))
+if (MSVC OR ARCH STREQUAL "i386")
     target_link_libraries(compiler_apitest ms_seh_test)
 endif()
 target_link_libraries(compiler_apitest wine ${PSEH_LIB})

modules/rostests/apitests/crt/CMakeLists.txt

@@ -1,5 +1,5 @@
 
-if (GCC)
+if(CMAKE_C_COMPILER_ID STREQUAL "GNU" OR CMAKE_C_COMPILER_ID STREQUAL "Clang")
     add_compile_options(-fno-builtin)
 endif()
 

modules/rostests/winetests/advapi32/CMakeLists.txt

@@ -21,7 +21,7 @@ add_executable(advapi32_winetest
     ${SOURCE}
     ${PCH_SKIP_SOURCE})
 
-if(USE_CLANG_CL OR (NOT MSVC))
+if(CMAKE_C_COMPILER_ID STREQUAL "GNU" OR CMAKE_C_COMPILER_ID STREQUAL "Clang")
     target_compile_options(advapi32_winetest PRIVATE "-Wno-format")
 endif()
 

modules/rostests/winetests/kernel32/CMakeLists.txt

@@ -56,7 +56,7 @@ if(MSVC)
     endif()
 endif()
 
-if(USE_CLANG_CL OR (NOT MSVC))
+if(CMAKE_C_COMPILER_ID STREQUAL "GNU" OR CMAKE_C_COMPILER_ID STREQUAL "Clang")
     target_compile_options(kernel32_winetest PRIVATE "-Wno-format")
 endif()
 

modules/rostests/winetests/msvcrt/CMakeLists.txt

@@ -27,11 +27,8 @@ target_compile_definitions(msvcrt_winetest PRIVATE
     _CRT_NONSTDC_NO_DEPRECATE
     __msvcrt_ulong=ULONG)
 
-if ((NOT MSVC) OR USE_CLANG_CL)
-    if (NOT USE_CLANG_CL)
-        target_compile_options(msvcrt_winetest PRIVATE -Wno-stringop-truncation)
-    endif()
-    target_compile_options(msvcrt_winetest PRIVATE -Wno-format)
+if(CMAKE_C_COMPILER_ID STREQUAL "GNU" OR CMAKE_C_COMPILER_ID STREQUAL "Clang")
+    target_compile_options(msvcrt_winetest PRIVATE -Wno-format -Wno-stringop-truncation)
 endif()
 
 set_module_type(msvcrt_winetest win32cui)

modules/rostests/winetests/ntdll/CMakeLists.txt

@@ -40,7 +40,7 @@ if(MSVC AND ARCH STREQUAL "amd64")
     target_compile_options(ntdll_winetest PRIVATE /wd4334)
 endif()
 
-if(USE_CLANG_CL OR (NOT MSVC))
+if(CMAKE_C_COMPILER_ID STREQUAL "GNU" OR CMAKE_C_COMPILER_ID STREQUAL "Clang")
     target_compile_options(ntdll_winetest PRIVATE "-Wno-format")
 endif()
 

modules/rostests/winetests/rpcrt4/CMakeLists.txt

@@ -40,11 +40,12 @@ endif()
 
 add_executable(rpcrt4_winetest ${SOURCE})
 
-if(USE_CLANG_CL OR (NOT MSVC))
+if(CMAKE_C_COMPILER_ID STREQUAL "GNU" OR CMAKE_C_COMPILER_ID STREQUAL "Clang")
     target_compile_options(rpcrt4_winetest PRIVATE "-Wno-format")
-    if(USE_CLANG_CL)
-        target_compile_options(rpcrt4_winetest PRIVATE "-Wno-cast-calling-convention")
-    endif()
+endif()
+
+if(CMAKE_C_COMPILER_ID STREQUAL "Clang")
+    target_compile_options(rpcrt4_winetest PRIVATE "-Wno-cast-calling-convention")
 endif()
 
 target_link_libraries(rpcrt4_winetest uuid wine ${PSEH_LIB})

modules/rostests/winetests/winmm/CMakeLists.txt

@@ -14,7 +14,7 @@ list(APPEND SOURCE
 
 add_executable(winmm_winetest ${SOURCE})
 
-if(USE_CLANG_CL OR (NOT MSVC))
+if(CMAKE_C_COMPILER_ID STREQUAL "GNU" OR CMAKE_C_COMPILER_ID STREQUAL "Clang")
     target_compile_options(winmm_winetest PRIVATE "-Wno-format")
 endif()
 

modules/rostests/winetests/ws2_32/CMakeLists.txt

@@ -3,7 +3,7 @@ include_directories(BEFORE ${REACTOS_SOURCE_DIR}/sdk/include/reactos/wine)
 
 add_executable(ws2_32_winetest protocol.c sock.c testlist.c)
 
-if(USE_CLANG_CL OR (NOT MSVC))
+if(CMAKE_C_COMPILER_ID STREQUAL "GNU" OR CMAKE_C_COMPILER_ID STREQUAL "Clang")
     target_compile_options(ws2_32_winetest PRIVATE "-Wno-format")
 endif()
 

ntoskrnl/CMakeLists.txt

@@ -1,18 +1,13 @@
 
 PROJECT(NTOS)
 
-if (GCC)
+if (CMAKE_C_COMPILER_ID STREQUAL "GNU" OR CMAKE_C_COMPILER_ID STREQUAL "Clang")
     # Enable this again. CORE-17637
     add_compile_options(-Wunused-result)
 endif()
 
 include(ntos.cmake)
 
-if(NOT MSVC)
-    # Make sure we don't duplicate some symbols
-    add_compile_options(-fno-common)
-endif()
-
 set(NTOSKRNL_SOURCE ${SOURCE})
 set(NTOSKRNL_ASM_SOURCE ${ASM_SOURCE})
 

sdk/cmake/config.cmake

@@ -75,25 +75,6 @@ else()
 "Whether to compile for debugging.")
 endif()
 
-if(CMAKE_C_COMPILER_ID STREQUAL "GNU")
-    set(GCC TRUE CACHE BOOL "The compiler is GCC")
-    set(CLANG FALSE CACHE BOOL "The compiler is LLVM Clang")
-elseif(CMAKE_C_COMPILER_ID STREQUAL "Clang")
-    # We can use LLVM Clang mimicking CL or GCC. Account for this
-    if (MSVC)
-        set(GCC FALSE CACHE BOOL "The compiler is GCC")
-    else()
-        set(GCC TRUE CACHE BOOL "The compiler is GCC")
-    endif()
-    set(CLANG TRUE CACHE BOOL "The compiler is LLVM Clang")
-elseif(MSVC) # aka CMAKE_C_COMPILER_ID STREQUAL "MSVC"
-    set(GCC FALSE CACHE BOOL "The compiler is GCC")
-    set(CLANG FALSE CACHE BOOL "The compiler is LLVM Clang")
-    # MSVC variable is already set by cmake
-else()
-    message("WARNING: the compiler has not been recognized")
-endif()
-
 if(MSVC)
     set(KDBG FALSE CACHE BOOL
 "Whether to compile in the integrated kernel debugger.")
@@ -102,7 +83,6 @@ if(MSVC)
     else()
         set(_WINKD_ TRUE CACHE BOOL "Whether to compile with the KD protocol.")
     endif()
-
 else()
     if(CMAKE_BUILD_TYPE STREQUAL "Release")
         set(KDBG FALSE CACHE BOOL "Whether to compile in the integrated kernel debugger.")
@@ -120,7 +100,7 @@ cmake_dependent_option(ISAPNP_ENABLE "Whether to enable the ISA PnP support." ON
 set(GENERATE_DEPENDENCY_GRAPH FALSE CACHE BOOL
 "Whether to create a GraphML dependency graph of DLLs.")
 
-if(MSVC)
+if(CMAKE_C_COMPILER_ID STREQUAL "MSVC")
     option(_PREFAST_ "Whether to enable PREFAST while compiling." OFF)
     option(_VS_ANALYZE_ "Whether to enable static analysis while compiling." OFF)
     # RTC are incompatible with compiler optimizations.
@@ -128,7 +108,7 @@ if(MSVC)
                            "CMAKE_BUILD_TYPE STREQUAL Debug" OFF)
 endif()
 
-if(GCC)
+if(CMAKE_C_COMPILER_ID STREQUAL "GNU")
     option(STACK_PROTECTOR "Whether to enable the GCC stack checker while compiling" OFF)
 endif()
 

sdk/cmake/gcc.cmake

@@ -485,12 +485,12 @@ add_compile_options("$<$<COMPILE_LANGUAGE:CXX>:$<IF:$<BOOL:$<TARGET_PROPERTY:WIT
 add_compile_options("$<$<COMPILE_LANGUAGE:CXX>:$<IF:$<BOOL:$<TARGET_PROPERTY:WITH_CXX_EXCEPTIONS>>,-fexceptions,-fno-exceptions>>")
 
 # G++ shipped with ROSBE uses sjlj exceptions on i386. Tell Clang it is so
-if (CLANG AND (ARCH STREQUAL "i386"))
+if(CMAKE_C_COMPILER_ID STREQUAL "Clang" AND ARCH STREQUAL "i386")
     add_compile_options("$<$<AND:$<COMPILE_LANGUAGE:CXX>,$<BOOL:$<TARGET_PROPERTY:WITH_CXX_EXCEPTIONS>>>:-fsjlj-exceptions>")
 endif()
 
 # Find default G++ libraries
-if (CLANG)
+if(CMAKE_C_COMPILER_ID STREQUAL "Clang")
     set(GXX_EXECUTABLE ${CMAKE_CXX_COMPILER_TARGET}-g++)
 else()
     set(GXX_EXECUTABLE ${CMAKE_CXX_COMPILER})

sdk/lib/3rdparty/freetype/CMakeLists.txt

@@ -58,6 +58,8 @@ add_library(freetype ${SOURCE})
 if(CMAKE_C_COMPILER_ID STREQUAL "MSVC" AND ARCH STREQUAL "amd64")
     # error C4312: 'type cast': conversion from 'unsigned long' to 'void *' of greater size
     remove_target_compile_option(freetype "/we4312")
-elseif(GCC)
+endif()
+
+if(CMAKE_C_COMPILER_ID STREQUAL "GNU" OR CMAKE_C_COMPILER_ID STREQUAL "Clang")
     target_compile_options(freetype PRIVATE -fno-builtin-malloc)
 endif()

sdk/lib/3rdparty/libxml2/CMakeLists.txt

@@ -64,7 +64,7 @@ list(APPEND SOURCE
 
 add_library(libxml2 ${SOURCE})
 
-if(MSVC AND (NOT USE_CLANG_CL))
+if(CMAKE_C_COMPILER_ID STREQUAL "MSVC")
     # Unreferenced local variable
     remove_target_compile_option(libxml2 "/we4101")
     target_compile_options(libxml2 PRIVATE "/wd4101")

sdk/lib/crt/msvcrtex.cmake

@@ -26,7 +26,7 @@ if(ARCH STREQUAL "i386")
         math/i386/alldiv_asm.s
         math/i386/aulldiv_asm.s
         )
-    if (GCC AND CLANG)
+    if (CMAKE_C_COMPILER_ID STREQUAL "Clang" AND NOT MSVC)
         list(APPEND MSVCRTEX_ASM_SOURCE
             math/i386/ceilf.S
             math/i386/floorf.S)
@@ -77,7 +77,7 @@ if(MSVC AND (ARCH STREQUAL "i386"))
 endif()
 
 
-if(GCC OR CLANG)
+if(CMAKE_C_COMPILER_ID STREQUAL "GNU" OR CMAKE_C_COMPILER_ID STREQUAL "Clang")
     target_compile_options(msvcrtex PRIVATE $<$<COMPILE_LANGUAGE:C>:-Wno-main>)
     if(LTCG)
         target_compile_options(msvcrtex PRIVATE -fno-lto)

sdk/lib/drivers/wdf/CMakeLists.txt

@@ -210,7 +210,7 @@ target_include_directories(wdf01000
 
 target_link_libraries(wdf01000 aux_klib ntoskrnl_vista ${PSEH_LIB})
 
-if(GCC)
+if(CMAKE_C_COMPILER_ID STREQUAL "GNU" OR CMAKE_C_COMPILER_ID STREQUAL "Clang")
     target_compile_options(wdf01000
         PRIVATE -Wno-write-strings -Wno-unknown-pragmas -Wno-switch
         PRIVATE $<$<COMPILE_LANGUAGE:CXX>:-Wno-reorder -Wno-invalid-offsetof -Wno-delete-non-virtual-dtor>)

sdk/lib/rtl/CMakeLists.txt

@@ -5,7 +5,7 @@ add_definitions(
     -D_NTSYSTEM_
     -D_NTDLLBUILD_)
 
-if (GCC)
+if (CMAKE_C_COMPILER_ID STREQUAL "GNU" OR CMAKE_C_COMPILER_ID STREQUAL "Clang")
     # Enable this again. CORE-17637
     add_compile_options(-Wunused-result)
 endif()