From 91425ccb6ff0a416b67ef21eb3ecebb49ba3e748 Mon Sep 17 00:00:00 2001
From: Ellie Hermaszewska <ellieh@nvidia.com>
Date: Tue, 6 May 2025 19:45:03 +0800
Subject: Update C++ standard to C++20 (#6980)

* Correct incorrect enum usage on metal

* Update C++ standard to C++20

Closes https://github.com/shader-slang/slang/issues/6945

* use bit_cast
---
 cmake/CompilerFlags.cmake              | 2 +-
 source/core/slang-io.cpp               | 2 +-
 source/slang/slang-ir.h                | 8 +-------
 tools/slang-test/slang-test-main.cpp   | 2 +-
 tools/test-server/test-server-main.cpp | 2 +-
 5 files changed, 5 insertions(+), 11 deletions(-)

diff --git a/cmake/CompilerFlags.cmake b/cmake/CompilerFlags.cmake
index 24a2c574f..2019b554b 100644
--- a/cmake/CompilerFlags.cmake
+++ b/cmake/CompilerFlags.cmake
@@ -175,7 +175,7 @@ function(set_default_compile_options target)
             ON
             # C++ standard
             CXX_STANDARD
-            17
+            20
             # pic
             POSITION_INDEPENDENT_CODE
             ON
diff --git a/source/core/slang-io.cpp b/source/core/slang-io.cpp
index 5490294ca..851c70073 100644
--- a/source/core/slang-io.cpp
+++ b/source/core/slang-io.cpp
@@ -752,7 +752,7 @@ String Path::getRelativePath(String base, String path)
     auto result = std::filesystem::relative(p2, p1, ec);
     if (ec)
         return path;
-    return String(UnownedStringSlice(result.generic_u8string().c_str()));
+    return String(reinterpret_cast<const char*>(result.generic_u8string().c_str()));
 }
 
 SlangResult Path::remove(const String& path)
diff --git a/source/slang/slang-ir.h b/source/slang/slang-ir.h
index ea784c9a6..5a1ae94f7 100644
--- a/source/slang/slang-ir.h
+++ b/source/slang/slang-ir.h
@@ -7,9 +7,6 @@
 // similar in spirit to LLVM (but much simpler).
 //
 
-#if defined(__cpp_lib_bit_cast)
-#include <bit>
-#endif
 #include "../compiler-core/slang-source-loc.h"
 #include "../compiler-core/slang-source-map.h"
 #include "../core/slang-basic.h"
@@ -17,6 +14,7 @@
 #include "slang-container-pool.h"
 #include "slang-type-system-shared.h"
 
+#include <bit>
 #include <functional>
 
 namespace Slang
@@ -105,11 +103,7 @@ enum IRMemoryOrder
 
 inline int32_t operator&(const IROpMask m, const IROp o)
 {
-#if defined(__cpp_lib_bit_cast)
     return std::bit_cast<int32_t>(m) & std::bit_cast<int32_t>(o);
-#else
-    return (int32_t)m & (int32_t)o;
-#endif
 }
 
 inline int32_t operator&(const IROp o, const IROpMask m)
diff --git a/tools/slang-test/slang-test-main.cpp b/tools/slang-test/slang-test-main.cpp
index c0697b4a4..1fb70ed03 100644
--- a/tools/slang-test/slang-test-main.cpp
+++ b/tools/slang-test/slang-test-main.cpp
@@ -58,7 +58,7 @@ extern "C"
 
 extern "C"
 {
-    __declspec(dllexport) extern const char* D3D12SDKPath = u8".\\D3D12\\";
+    __declspec(dllexport) extern const char* D3D12SDKPath = ".\\D3D12\\";
 }
 #endif
 
diff --git a/tools/test-server/test-server-main.cpp b/tools/test-server/test-server-main.cpp
index 63535ec92..3faa6352f 100644
--- a/tools/test-server/test-server-main.cpp
+++ b/tools/test-server/test-server-main.cpp
@@ -28,7 +28,7 @@ extern "C"
 
 extern "C"
 {
-    __declspec(dllexport) extern const char* D3D12SDKPath = u8".\\D3D12\\";
+    __declspec(dllexport) extern const char* D3D12SDKPath = ".\\D3D12\\";
 }
 #endif
 
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