From eaf046c576ebcd123b0d9b4c6ee59a8c3ae410c5 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Micha=C5=82=20Petryka?=
 <35800402+MichalPetryka@users.noreply.github.com>
Date: Fri, 1 Mar 2024 02:36:54 +0100
Subject: [PATCH 1/2] Fix GC hole in Guid

Found in #99130.
---
 .../System.Private.CoreLib/src/System/Guid.cs        | 12 ++++--------
 1 file changed, 4 insertions(+), 8 deletions(-)

diff --git a/src/libraries/System.Private.CoreLib/src/System/Guid.cs b/src/libraries/System.Private.CoreLib/src/System/Guid.cs
index b6946be5ec578b..7e3bb700263845 100644
--- a/src/libraries/System.Private.CoreLib/src/System/Guid.cs
+++ b/src/libraries/System.Private.CoreLib/src/System/Guid.cs
@@ -841,10 +841,6 @@ private static bool IsHexPrefix(ReadOnlySpan<char> str, int i) =>
             str[i] == '0' &&
             (str[i + 1] | 0x20) == 'x';
 
-        [MethodImpl(MethodImplOptions.AggressiveInlining)]
-        private static unsafe ReadOnlySpan<byte> AsBytes(in Guid source) =>
-            new ReadOnlySpan<byte>(Unsafe.AsPointer(ref Unsafe.AsRef(in source)), sizeof(Guid));
-
         // Returns an unsigned byte array containing the GUID.
         public byte[] ToByteArray()
         {
@@ -856,7 +852,7 @@ public byte[] ToByteArray()
             else
             {
                 // slower path for BigEndian
-                Guid guid = new Guid(AsBytes(this), false);
+                Guid guid = new Guid(MemoryMarshal.AsBytes(new ReadOnlySpan<Guid>(this)), false);
                 MemoryMarshal.TryWrite(g, in guid);
             }
             return g;
@@ -874,7 +870,7 @@ public byte[] ToByteArray(bool bigEndian)
             else
             {
                 // slower path for Reverse
-                Guid guid = new Guid(AsBytes(this), bigEndian);
+                Guid guid = new Guid(MemoryMarshal.AsBytes(new ReadOnlySpan<Guid>(this)), bigEndian);
                 MemoryMarshal.TryWrite(g, in guid);
             }
             return g;
@@ -893,7 +889,7 @@ public bool TryWriteBytes(Span<byte> destination)
             else
             {
                 // slower path for BigEndian
-                Guid guid = new Guid(AsBytes(this), false);
+                Guid guid = new Guid(MemoryMarshal.AsBytes(new ReadOnlySpan<Guid>(this)), false);
                 MemoryMarshal.TryWrite(destination, in guid);
             }
             return true;
@@ -915,7 +911,7 @@ public bool TryWriteBytes(Span<byte> destination, bool bigEndian, out int bytesW
             else
             {
                 // slower path for Reverse
-                Guid guid = new Guid(AsBytes(this), bigEndian);
+                Guid guid = new Guid(MemoryMarshal.AsBytes(new ReadOnlySpan<Guid>(this)), bigEndian);
                 MemoryMarshal.TryWrite(destination, in guid);
             }
             bytesWritten = 16;

From bfdbcae5ff0f4c6d6d35adaab11e9db2ae4819ee Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Micha=C5=82=20Petryka?=
 <35800402+MichalPetryka@users.noreply.github.com>
Date: Fri, 1 Mar 2024 02:48:37 +0100
Subject: [PATCH 2/2] Add missing in

---
 src/libraries/System.Private.CoreLib/src/System/Guid.cs | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/src/libraries/System.Private.CoreLib/src/System/Guid.cs b/src/libraries/System.Private.CoreLib/src/System/Guid.cs
index 7e3bb700263845..911fb9f7184a30 100644
--- a/src/libraries/System.Private.CoreLib/src/System/Guid.cs
+++ b/src/libraries/System.Private.CoreLib/src/System/Guid.cs
@@ -852,7 +852,7 @@ public byte[] ToByteArray()
             else
             {
                 // slower path for BigEndian
-                Guid guid = new Guid(MemoryMarshal.AsBytes(new ReadOnlySpan<Guid>(this)), false);
+                Guid guid = new Guid(MemoryMarshal.AsBytes(new ReadOnlySpan<Guid>(in this)), false);
                 MemoryMarshal.TryWrite(g, in guid);
             }
             return g;
@@ -870,7 +870,7 @@ public byte[] ToByteArray(bool bigEndian)
             else
             {
                 // slower path for Reverse
-                Guid guid = new Guid(MemoryMarshal.AsBytes(new ReadOnlySpan<Guid>(this)), bigEndian);
+                Guid guid = new Guid(MemoryMarshal.AsBytes(new ReadOnlySpan<Guid>(in this)), bigEndian);
                 MemoryMarshal.TryWrite(g, in guid);
             }
             return g;
@@ -889,7 +889,7 @@ public bool TryWriteBytes(Span<byte> destination)
             else
             {
                 // slower path for BigEndian
-                Guid guid = new Guid(MemoryMarshal.AsBytes(new ReadOnlySpan<Guid>(this)), false);
+                Guid guid = new Guid(MemoryMarshal.AsBytes(new ReadOnlySpan<Guid>(in this)), false);
                 MemoryMarshal.TryWrite(destination, in guid);
             }
             return true;
@@ -911,7 +911,7 @@ public bool TryWriteBytes(Span<byte> destination, bool bigEndian, out int bytesW
             else
             {
                 // slower path for Reverse
-                Guid guid = new Guid(MemoryMarshal.AsBytes(new ReadOnlySpan<Guid>(this)), bigEndian);
+                Guid guid = new Guid(MemoryMarshal.AsBytes(new ReadOnlySpan<Guid>(in this)), bigEndian);
                 MemoryMarshal.TryWrite(destination, in guid);
             }
             bytesWritten = 16;