From 89a01843ee090db671670dc22e1996a2bd625e3d Mon Sep 17 00:00:00 2001
From: Duncan Horn <40036384+dunhor@users.noreply.github.com>
Date: Sat, 8 Jun 2024 12:41:04 -0700
Subject: [PATCH] Fix compilation when using Clang in "MSVC mode" (#2221)

When using Clang in "MSVC mode" (i.e. clang-cl), command line arguments
are interpreted as MSVC would interpret them, at least when there are
conflicts. This means that `-Wall` - potentially among other switches -
is interpreted _dramatically_ differently by clang-cl compared to
"normal" Clang.

In CMake, this can be detected by testing for `if (MSVC)` in addition to
compiler id test, which is what I do here.

Note: this is a partial cherry-pick from #2095, which I'm going to go
through and break into smaller pieces in hopes of getting some things in
while discussion of other things can continue.
---
 CMakeLists.txt | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/CMakeLists.txt b/CMakeLists.txt
index 822056b91..51c8c0814 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -107,7 +107,7 @@ endif ()
 # aggressive about diagnosing build problems; this can get
 # relaxed somewhat in final shipping versions.
 IF (CMAKE_C_COMPILER_ID MATCHES "^GNU$" OR
-    CMAKE_C_COMPILER_ID MATCHES "^Clang$")
+    CMAKE_C_COMPILER_ID MATCHES "^Clang$" AND NOT MSVC)
   SET(CMAKE_REQUIRED_FLAGS "-Wall -Wformat -Wformat-security")
   #################################################################
   # Set compile flags for all build types.
@@ -144,7 +144,7 @@ IF (CMAKE_C_COMPILER_ID MATCHES "^GNU$" OR
     SET(CMAKE_SHARED_LINKER_FLAGS "${CMAKE_SHARED_LINKER_FLAGS} -Wl,-dead_strip")
   ENDIF(NOT CMAKE_SYSTEM_NAME MATCHES "Darwin")
 ENDIF (CMAKE_C_COMPILER_ID MATCHES "^GNU$" OR
-       CMAKE_C_COMPILER_ID MATCHES "^Clang$")
+       CMAKE_C_COMPILER_ID MATCHES "^Clang$" AND NOT MSVC)
 IF (CMAKE_C_COMPILER_ID MATCHES "^XL$")
   SET(CMAKE_C_COMPILER "xlc_r")
   SET(CMAKE_REQUIRED_FLAGS "-qflag=e:e -qformat=sec")
-- 
2.47.2