From 5a9f324a46451f660f9bcc1da455a33c60c0ea29 Mon Sep 17 00:00:00 2001
From: Alexandru Croitor <alexandru.croitor@qt.io>
Date: Mon, 14 Oct 2024 16:12:31 +0200
Subject: [PATCH] CMake: Guard some MSVC flags not understood by clang-cl
 frontend

Due to various reasons, Qt WebEngine needs to be built with clang-cl,
while qtbase and other dependencies with MSVC.

clang-cl does not understand all MSVC-style options, which are
recorded and propagated through the PlatformCommonInternal target
which is configured in qtbase using MSVC.

Guard the flags that are not understood by clang-cl with a genex
condition that checks that the compiler is not clang (which implies
clang-cl, because afaik it's not possible to use gcc frontend of clang
against an MSVC-built qtbase).

Change-Id: Ibf2c96399a8322ce13814c9c6afa5b57fd8885be
Reviewed-by: Alexey Edelev <alexey.edelev@qt.io>
Reviewed-by: Zhao Yuhang <2546789017@qq.com>
Reviewed-by: Oliver Wolff <oliver.wolff@qt.io>
Reviewed-by: Allan Sandfeld Jensen <allan.jensen@qt.io>
(cherry picked from commit 515ad07a12c4bf190545ae38eff588f7b979d68e)
Reviewed-by: Qt Cherry-pick Bot <cherrypick_bot@qt-project.org>
---
 cmake/QtInternalTargets.cmake | 13 ++++++++++---
 1 file changed, 10 insertions(+), 3 deletions(-)

diff --git a/cmake/QtInternalTargets.cmake b/cmake/QtInternalTargets.cmake
index b95257cc69e..89d0f893e9b 100644
--- a/cmake/QtInternalTargets.cmake
+++ b/cmake/QtInternalTargets.cmake
@@ -262,6 +262,13 @@ endif()
 # Taken from mkspecs/common/msvc-version.conf and mkspecs/common/msvc-desktop.conf
 if (MSVC AND NOT CLANG)
     if (MSVC_VERSION GREATER_EQUAL 1799)
+        set_target_properties(PlatformCommonInternal PROPERTIES _qt_cpp_compiler_frontend_variant
+            "${CMAKE_CXX_COMPILER_FRONTEND_VARIANT}")
+
+        # Protect against adding these flags when building qtbase with MSVC, and qtwebengine using
+        # clang-cl.
+        set(is_not_clang_cl_start "$<$<NOT:$<STREQUAL:$<CXX_COMPILER_ID>,Clang>>:")
+        set(is_not_clang_cl_end ">")
         target_compile_options(PlatformCommonInternal INTERFACE
             -FS
             -Zc:rvalueCast
@@ -271,18 +278,18 @@ if (MSVC AND NOT CLANG)
     if (MSVC_VERSION GREATER_EQUAL 1899)
         target_compile_options(PlatformCommonInternal INTERFACE
             -Zc:strictStrings
-            -Zc:throwingNew
+            "${is_not_clang_cl_start}-Zc:throwingNew${is_not_clang_cl_end}"
         )
     endif()
     if (MSVC_VERSION GREATER_EQUAL 1909) # MSVC 2017
         target_compile_options(PlatformCommonInternal INTERFACE
-            -Zc:referenceBinding
+            "${is_not_clang_cl_start}-Zc:referenceBinding${is_not_clang_cl_end}"
             -Zc:ternary
         )
     endif()
     if (MSVC_VERSION GREATER_EQUAL 1919) # MSVC 2019
         target_compile_options(PlatformCommonInternal INTERFACE
-            -Zc:externConstexpr
+            "${is_not_clang_cl_start}-Zc:externConstexpr${is_not_clang_cl_end}"
             #-Zc:lambda # Buggy. TODO: Enable again when stable enough.
             #-Zc:preprocessor # breaks build due to bug in default Windows SDK 10.0.19041
         )