From f020c3e3ca0d9a9bea12f23ff7235afb7f4b7777 Mon Sep 17 00:00:00 2001
From: Omair Majid <omajid@redhat.com>
Date: Tue, 21 May 2024 18:19:09 -0400
Subject: [PATCH] Support building against clang 18

This is a targeted backport from a few other PRs that makes it possible
to build dotnet/runtme's 6.0 branch on Fedora 40 which includes clang
18.

- https://github.com/dotnet/arcade/pull/14572
- https://github.com/dotnet/runtime/pull/94782
- https://github.com/dotnet/runtime/pull/99811
---
 eng/native/configurecompiler.cmake            | 3 +++
 eng/native/init-compiler.sh                   | 2 +-
 src/coreclr/pal/src/include/pal/palinternal.h | 1 +
 src/libraries/Native/Unix/CMakeLists.txt      | 3 +++
 4 files changed, 8 insertions(+), 1 deletion(-)

diff --git a/eng/native/configurecompiler.cmake b/eng/native/configurecompiler.cmake
index 1a43b710c618b..88b3cd93745ca 100644
--- a/eng/native/configurecompiler.cmake
+++ b/eng/native/configurecompiler.cmake
@@ -376,6 +376,9 @@ if (CLR_CMAKE_HOST_UNIX)
     add_compile_options(-Wno-single-bit-bitfield-constant-conversion)
     add_compile_options(-Wno-cast-function-type-strict)
     add_compile_options(-Wno-incompatible-function-pointer-types-strict)
+
+    # clang 18.1 supressions
+    add_compile_options(-Wno-switch-default)
   else()
     add_compile_options(-Wno-unknown-pragmas)
     add_compile_options(-Wno-uninitialized)
diff --git a/eng/native/init-compiler.sh b/eng/native/init-compiler.sh
index e215bd75ff158..04761fe1b482f 100755
--- a/eng/native/init-compiler.sh
+++ b/eng/native/init-compiler.sh
@@ -46,7 +46,7 @@ if [[ -z "$CLR_CC" ]]; then
     # Set default versions
     if [[ -z "$majorVersion" ]]; then
         # note: gcc (all versions) and clang versions higher than 6 do not have minor version in file name, if it is zero.
-        if [[ "$compiler" == "clang" ]]; then versions=( 16 15 14 13 12 11 10 9 8 7 6.0 5.0 4.0 3.9 3.8 3.7 3.6 3.5 )
+        if [[ "$compiler" == "clang" ]]; then versions=( 18 17 16 15 14 13 12 11 10 9 8 7 6.0 5.0 4.0 3.9 3.8 3.7 3.6 3.5 )
         elif [[ "$compiler" == "gcc" ]]; then versions=( 12 11 10 9 8 7 6 5 4.9 ); fi
 
         for version in "${versions[@]}"; do
diff --git a/src/coreclr/pal/src/include/pal/palinternal.h b/src/coreclr/pal/src/include/pal/palinternal.h
index 4c7644db9ebe9..3fc42942be695 100644
--- a/src/coreclr/pal/src/include/pal/palinternal.h
+++ b/src/coreclr/pal/src/include/pal/palinternal.h
@@ -430,6 +430,7 @@ function_name() to call the system's implementation
 #undef va_list
 #undef va_start
 #undef va_end
+#undef va_arg
 #undef va_copy
 #undef stdin
 #undef stdout
diff --git a/src/libraries/Native/Unix/CMakeLists.txt b/src/libraries/Native/Unix/CMakeLists.txt
index cc14d13da1281..d6a53c3a9cde7 100644
--- a/src/libraries/Native/Unix/CMakeLists.txt
+++ b/src/libraries/Native/Unix/CMakeLists.txt
@@ -60,6 +60,9 @@ if(CMAKE_C_COMPILER_ID STREQUAL Clang)
     add_compile_options(-Wno-single-bit-bitfield-constant-conversion)
     add_compile_options(-Wno-cast-function-type-strict)
     add_compile_options(-Wno-incompatible-function-pointer-types-strict)
+
+    # clang 18.1 supressions
+    add_compile_options(-Wno-switch-default)
 elseif(CMAKE_C_COMPILER_ID STREQUAL GNU)
     add_compile_options(-Wno-stringop-truncation)
 endif()