From 4b694032dfe61dd9190170d15ee2edddbc9dfd7c Mon Sep 17 00:00:00 2001
From: Yuhang Zhao <2546789017@qq.com>
Date: Mon, 2 Nov 2020 12:36:14 +0800
Subject: [PATCH] Improve clang-cl support for Qt6

1. clang-cl doesn't support "-fno-exceptions", it uses msvc's parameter.
2. some parameters supported by msvc are not supported by clang-cl
and they are causing huge warning message flood, don't add them.
3. use correct optimize parameter for clang-cl.

Change-Id: Idbadf139127143c5fa6c49068588cb26f47da7a2
Reviewed-by: Alexandru Croitor <alexandru.croitor@qt.io>
---
 cmake/QtCompilerOptimization.cmake |  5 +++++
 cmake/QtFlagHandlingHelpers.cmake  | 21 ++++++++++++++-------
 cmake/QtInternalTargets.cmake      | 10 +++++++---
 3 files changed, 26 insertions(+), 10 deletions(-)

diff --git a/cmake/QtCompilerOptimization.cmake b/cmake/QtCompilerOptimization.cmake
index 2e98dc31c2a..333cbf3f155 100644
--- a/cmake/QtCompilerOptimization.cmake
+++ b/cmake/QtCompilerOptimization.cmake
@@ -158,6 +158,11 @@ if(MSVC)
     set(QT_CFLAGS_OPTIMIZE_DEBUG "-Od")
     set(QT_CFLAGS_OPTIMIZE_SIZE "-O1")
     set(QT_CFLAGS_OPTIMIZE_VALID_VALUES "/O2" "/O1" "/Od" "/Ob0" "/Ob1" "/Ob2" "/O0" "-O0")
+
+    if(CLANG)
+        set(QT_CFLAGS_OPTIMIZE_FULL "/clang:-O3")
+        set(QT_CFLAGS_OPTIMIZE_SIZE "/clang:-Oz")
+    endif()
 endif()
 
 # Android Clang
diff --git a/cmake/QtFlagHandlingHelpers.cmake b/cmake/QtFlagHandlingHelpers.cmake
index 2b6430a229c..b9835a36394 100644
--- a/cmake/QtFlagHandlingHelpers.cmake
+++ b/cmake/QtFlagHandlingHelpers.cmake
@@ -92,7 +92,7 @@ function(qt_internal_apply_gc_binaries target visibility)
         message(FATAL_ERROR "Visibitily setting must be one of PRIVATE, INTERFACE or PUBLIC.")
     endif()
 
-    if ((GCC OR CLANG) AND NOT EMSCRIPTEN AND NOT UIKIT)
+    if ((GCC OR CLANG) AND NOT EMSCRIPTEN AND NOT UIKIT AND NOT MSVC)
         if(APPLE)
             set(gc_sections_flag "-Wl,-dead_strip")
         elseif(SOLARIS)
@@ -105,7 +105,7 @@ function(qt_internal_apply_gc_binaries target visibility)
         target_link_options("${target}" ${visibility} "${gc_sections_flag}")
     endif()
 
-    if((GCC OR CLANG OR ICC) AND NOT EMSCRIPTEN AND NOT UIKIT)
+    if((GCC OR CLANG OR ICC) AND NOT EMSCRIPTEN AND NOT UIKIT AND NOT MSVC)
         set(split_sections_flags "-ffunction-sections" "-fdata-sections")
     endif()
     if(split_sections_flags)
@@ -149,15 +149,22 @@ endfunction()
 function(qt_internal_set_no_exceptions_flags target)
     target_compile_definitions("${target}" PRIVATE "QT_NO_EXCEPTIONS")
     if ("${CMAKE_CXX_COMPILER_ID}" STREQUAL "MSVC")
-        target_compile_options("${target}" PRIVATE "/wd4530" "/wd4577")
+        set(_flag "/wd4530" "/wd4577")
     elseif ("${CMAKE_CXX_COMPILER_ID}" STREQUAL "GNU")
-        target_compile_options("${target}" PRIVATE "-fno-exceptions")
+        set(_flag "-fno-exceptions")
     elseif ("${CMAKE_CXX_COMPILER_ID}" STREQUAL "AppleClang")
-        target_compile_options("${target}" PRIVATE "-fno-exceptions")
+        set(_flag "-fno-exceptions")
     elseif ("${CMAKE_CXX_COMPILER_ID}" STREQUAL "Clang")
-        target_compile_options("${target}" PRIVATE "-fno-exceptions")
+        if (MSVC)
+            set(_flag "/wd4530" "/wd4577")
+        else()
+            set(_flag "-fno-exceptions")
+        endif()
     elseif ("${CMAKE_CXX_COMPILER_ID}" STREQUAL "Intel")
-        target_compile_options("${target}" PRIVATE "-fno-exceptions")
+        set(_flag "-fno-exceptions")
+    endif()
+    if (_flag)
+        target_compile_options("${target}" PRIVATE ${_flag})
     endif()
 endfunction()
 
diff --git a/cmake/QtInternalTargets.cmake b/cmake/QtInternalTargets.cmake
index 91a75983ea1..cdaa91ffcb4 100644
--- a/cmake/QtInternalTargets.cmake
+++ b/cmake/QtInternalTargets.cmake
@@ -178,15 +178,19 @@ if (MSVC)
     if (MSVC_VERSION GREATER_EQUAL 1899)
         target_compile_options(PlatformCommonInternal INTERFACE
             -Zc:strictStrings
-            -Zc:throwingNew
         )
+        if (NOT CLANG)
+            target_compile_options(PlatformCommonInternal INTERFACE
+                -Zc:throwingNew
+            )
+        endif()
     endif()
-    if (MSVC_VERSION GREATER_EQUAL 1909)
+    if (MSVC_VERSION GREATER_EQUAL 1909 AND NOT CLANG)
         target_compile_options(PlatformCommonInternal INTERFACE
             -Zc:referenceBinding
         )
     endif()
-    if (MSVC_VERSION GREATER_EQUAL 1919)
+    if (MSVC_VERSION GREATER_EQUAL 1919 AND NOT CLANG)
         target_compile_options(PlatformCommonInternal INTERFACE
             -Zc:externConstexpr
         )