[corlib] Moved ValueType field into another class.

Adding fields to ValueType can mess with sub class layouts.
Fixes #30060.

diff --git a/mcs/class/corlib/System/ValueType.cs b/mcs/class/corlib/System/ValueType.cs
index 52bea0dcaf7c88aa46ab03f86bea90d1d739b9db..2956ffb317c034e67c8d92aec692adaedf53afd2 100644 (file)
--- a/mcs/class/corlib/System/ValueType.cs
+++ b/mcs/class/corlib/System/ValueType.cs
@@ -51,6 +51,15 @@ namespace System
        [ComVisible (true)]
        public abstract class ValueType
        {
+               /*
+                * Caution: Fields added to ValueType can mess with sub class layouts.
+                * Causing bugs that appear completely unrelated as #30060
+                */
+               private static class Internal
+               {
+                       public static int hash_code_of_ptr_seed = 0;
+               }
+
                protected ValueType ()
                {
                }
@@ -123,20 +132,18 @@ namespace System
                        return result;
                }
 
-               static int hash_code_of_ptr_seed = 0;
-
                internal static int GetHashCodeOfPtr (IntPtr ptr)
                {
                        int hash_code = (int) ptr;
-                       int seed = hash_code_of_ptr_seed;
+                       int seed = Internal.hash_code_of_ptr_seed;
 
                        if (seed == 0) {
                                /* We use the first non-0 pointer as the seed, all hashcodes will be
                                 * based off that. This is to make sure that we only reveal relative
                                 * memory addresses and never absolute ones. */
                                seed = hash_code;
-                               Interlocked.CompareExchange (ref hash_code_of_ptr_seed, seed, 0);
-                               seed = hash_code_of_ptr_seed;
+                               Interlocked.CompareExchange (ref Internal.hash_code_of_ptr_seed, seed, 0);
+                               seed = Internal.hash_code_of_ptr_seed;
                        }
 
                        return hash_code - seed;