Return iOS version in Environment.OSVersion on Mac Catalyst (#50990)

* Return iOS version in Environment.OSVersion on Mac Catalyst.
Implement OperatingSystem.IsMacCatalyst and OperatingSystem.IsMacCatalystVersionAtLeast.

* Address feedback

* Ensure NSThread is in multi-threaded mode before using autorelease pool

src/libraries/Common/src/Interop/OSX/System.Native/Interop.iOSSupportVersion.cs

+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+
+using System;
+using System.Runtime.InteropServices;
+
+internal static partial class Interop
+{
+    internal static partial class Sys
+    {
+        [DllImport(Libraries.SystemNative, EntryPoint = "SystemNative_iOSSupportVersion")]
+        internal static extern string iOSSupportVersion();
+    }
+}

src/libraries/Native/Unix/System.Native/CMakeLists.txt

@@ -47,6 +47,14 @@ else ()
         pal_log.c)
 endif ()
 
+if (CLR_CMAKE_TARGET_MACCATALYST)
+    set(NATIVE_SOURCES ${NATIVE_SOURCES}
+        pal_iossupportversion.m)
+else ()
+    list (APPEND NATIVE_SOURCES
+        pal_iossupportversion.c)
+endif ()
+
 if (NOT CLR_CMAKE_TARGET_BROWSER)
     list (APPEND NATIVE_SOURCES pal_networkchange.c)
 endif ()

src/libraries/Native/Unix/System.Native/entrypoints.c

@@ -10,6 +10,7 @@
 #include "pal_errno.h"
 #include "pal_interfaceaddresses.h"
 #include "pal_io.h"
+#include "pal_iossupportversion.h"
 #include "pal_log.h"
 #include "pal_memory.h"
 #include "pal_mount.h"
@@ -237,6 +238,7 @@ static const Entry s_sysNative[] =
     DllImportEntry(SystemNative_LowLevelMonitor_Create)
     DllImportEntry(SystemNative_CreateAutoreleasePool)
     DllImportEntry(SystemNative_DrainAutoreleasePool)
+    DllImportEntry(SystemNative_iOSSupportVersion)
 };
 
 EXTERN_C const void* SystemResolveDllImport(const char* name);

src/libraries/Native/Unix/System.Native/pal_autoreleasepool.h

@@ -15,3 +15,9 @@ PALEXPORT void* SystemNative_CreateAutoreleasePool(void);
  * Drains and releases a pool created by SystemNative_CreateAutoreleasePool.
  */
 PALEXPORT void SystemNative_DrainAutoreleasePool(void* pool);
+
+/**
+ * Ensure that NSThread is in multi-threading mode when POSIX APIs are used to
+ * start new threads.
+ */
+void EnsureNSThreadIsMultiThreaded(void);

src/libraries/Native/Unix/System.Native/pal_autoreleasepool.m

@@ -15,7 +15,7 @@
 }
 @end
 
-void* SystemNative_CreateAutoreleasePool(void)
+void EnsureNSThreadIsMultiThreaded(void)
 {
     if (![NSThread isMultiThreaded])
     {
@@ -30,7 +30,11 @@ void* SystemNative_CreateAutoreleasePool(void)
         [NSThread detachNewThreadSelector:@selector(noop:) toTarget:placeholderObject withObject:nil];
     }
     assert([NSThread isMultiThreaded]);
+}
 
+void* SystemNative_CreateAutoreleasePool(void)
+{
+    EnsureNSThreadIsMultiThreaded();
     return [[NSAutoreleasePool alloc] init];
 }
 

src/libraries/Native/Unix/System.Native/pal_iossupportversion.c

+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+
+#include "pal_iossupportversion.h"
+#include <stdlib.h>
+#include "pal_utilities.h"
+
+// These functions should not be used, but they need to be defined
+// to satisfy the tooling we used to enable redirecting P/Invokes
+// for the single file scenario.
+const char* SystemNative_iOSSupportVersion(void)
+{
+    assert_err(false, "iOS support not available on this platform.", EINVAL);
+    return NULL;
+}

src/libraries/Native/Unix/System.Native/pal_iossupportversion.h

+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+
+#pragma once
+
+#include "pal_compiler.h"
+#include "pal_types.h"
+
+PALEXPORT const char* SystemNative_iOSSupportVersion(void);

src/libraries/Native/Unix/System.Native/pal_iossupportversion.m

+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+
+#include "pal_iossupportversion.h"
+#include "pal_autoreleasepool.h"
+#import <Foundation/Foundation.h>
+
+const char* SystemNative_iOSSupportVersion()
+{
+    EnsureNSThreadIsMultiThreaded();
+
+    @autoreleasepool
+    {
+        NSDictionary *plist = [NSDictionary dictionaryWithContentsOfFile:@"/System/Library/CoreServices/SystemVersion.plist"];
+        NSString *iOSSupportVersion = (NSString *)[plist objectForKey:@"iOSSupportVersion"];
+        return strdup([iOSSupportVersion UTF8String]);
+    }
+}

src/libraries/System.Private.CoreLib/src/System.Private.CoreLib.Shared.projitems

@@ -1847,7 +1847,8 @@
     <Compile Include="$(MSBuildThisFileDirectory)System\Diagnostics\Tracing\RuntimeEventSourceHelper.Unix.cs" Condition="'$(FeaturePerfTracing)' == 'true'" />
     <Compile Include="$(MSBuildThisFileDirectory)System\Environment.NoRegistry.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)System\Environment.UnixOrBrowser.cs" />
-    <Compile Include="$(MSBuildThisFileDirectory)System\Environment.OSVersion.OSX.cs" Condition="'$(IsOSXLike)' == 'true'" />
+    <Compile Include="$(MSBuildThisFileDirectory)System\Environment.OSVersion.OSX.cs" Condition="'$(IsOSXLike)' == 'true' AND '$(TargetsMacCatalyst)' != 'true'" />
+    <Compile Include="$(MSBuildThisFileDirectory)System\Environment.OSVersion.MacCatalyst.cs" Condition="'$(TargetsMacCatalyst)' == 'true'" />
     <Compile Include="$(MSBuildThisFileDirectory)System\Environment.GetFolderPathCore.Unix.cs" Condition="'$(IsiOSLike)' != 'true'" />
     <Compile Include="$(MSBuildThisFileDirectory)System\Globalization\CalendarData.Unix.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)System\Globalization\CultureData.Unix.cs" />
@@ -1924,6 +1925,10 @@
     <Compile Include="$(CommonPath)Interop\OSX\System.Native\Interop.AutoreleasePool.cs"
              Link="Common\Interop\OSX\System.Native\Interop.AutoreleasePool.cs" />
   </ItemGroup>
+  <ItemGroup Condition="'$(TargetsMacCatalyst)' == 'true'">
+    <Compile Include="$(CommonPath)Interop\OSX\System.Native\Interop.iOSSupportVersion.cs"
+             Link="Common\Interop\OSX\System.Native\Interop.iOSSupportVersion.cs" />
+  </ItemGroup>
   <ItemGroup Condition="'$(SupportsX86Intrinsics)' == 'true'">
     <Compile Include="$(MSBuildThisFileDirectory)System\Runtime\Intrinsics\X86\Aes.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)System\Runtime\Intrinsics\X86\Avx.cs" />

src/libraries/System.Private.CoreLib/src/System/Environment.OSVersion.MacCatalyst.cs

+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+
+namespace System
+{
+    public static partial class Environment
+    {
+        private static OperatingSystem GetOSVersion()
+        {
+            Version version = new Version(Interop.Sys.iOSSupportVersion());
+            return new OperatingSystem(PlatformID.Unix, version);
+        }
+    }
+}

src/libraries/System.Private.CoreLib/src/System/OperatingSystem.cs

@@ -203,7 +203,6 @@ public static bool IsIOSVersionAtLeast(int major, int minor = 0, int build = 0)
         public static bool IsMacOSVersionAtLeast(int major, int minor = 0, int build = 0)
             => IsMacOS() && IsOSVersionAtLeast(major, minor, build, 0);
 
-/* Commented out for now, until we're ready to make changes to the public API
         /// <summary>
         /// Indicates whether the current application is running on Mac Catalyst.
         /// </summary>
@@ -215,11 +214,10 @@ public static bool IsMacOSVersionAtLeast(int major, int minor = 0, int build = 0
 #endif
 
         /// <summary>
-        /// Check for the Mac Catalyst version (returned by 'libobjc.get_operatingSystemVersion') with a >= version comparison. Used to guard APIs that were added in the given Mac Catalyst release.
+        /// Check for the Mac Catalyst version (iOS version as presented in Apple documentation) with a >= version comparison. Used to guard APIs that were added in the given Mac Catalyst release.
         /// </summary>
         public static bool IsMacCatalystVersionAtLeast(int major, int minor = 0, int build = 0)
             => IsMacCatalyst() && IsOSVersionAtLeast(major, minor, build, 0);
-*/
 
         /// <summary>
         /// Indicates whether the current application is running on tvOS.

src/libraries/System.Runtime/ref/System.Runtime.cs

@@ -3107,6 +3107,8 @@ public sealed partial class OperatingSystem : System.ICloneable, System.Runtime.
         public static bool IsIOSVersionAtLeast(int major, int minor = 0, int build = 0) { throw null; }
         public static bool IsMacOS() { throw null; }
         public static bool IsMacOSVersionAtLeast(int major, int minor = 0, int build = 0) { throw null; }
+        public static bool IsMacCatalyst() { throw null; }
+        public static bool IsMacCatalystVersionAtLeast(int major, int minor = 0, int build = 0) { throw null; }
         public static bool IsTvOS() { throw null; }
         public static bool IsTvOSVersionAtLeast(int major, int minor = 0, int build = 0) { throw null; }
         public static bool IsWatchOS() { throw null; }