Fix it so that disposing the RocksDb instance twice does not throw AccessViolationException and crash the process. Introduce dtor to ensure disposal, even if reference is lost.

Author: mookid8000

RocksDbSharp/RocksDb.cs

@@ -5,11 +5,14 @@
 using System.Runtime.InteropServices;
 using System.Text;
 using Transitional;
+// ReSharper disable EmptyGeneralCatchClause
 
 namespace RocksDbSharp
 {
     public class RocksDb : IDisposable
     {
+        bool disposed;
+
         internal static ReadOptions DefaultReadOptions { get; } = new ReadOptions();
         internal static OptionsHandle DefaultOptions { get; } = new DbOptions();
         internal static WriteOptions DefaultWriteOptions { get; } = new WriteOptions();
@@ -29,13 +32,36 @@ private RocksDb(IntPtr handle, dynamic optionsReferences, dynamic cfOptionsRefs,
             this.columnFamilies = columnFamilies;
         }
 
+        ~RocksDb()
+        {
+            ReleaseUnmanagedResources();
+        }
+
         public void Dispose()
+        {
+            if (disposed) return;
+
+            try
+            {
+                ReleaseUnmanagedResources();
+                GC.SuppressFinalize(this);
+            }
+            finally
+            {
+                disposed = true;
+            }
+        }
+
+        void ReleaseUnmanagedResources()
         {
             if (columnFamilies != null)
             {
                 foreach (var cfh in columnFamilies.Values)
+                {
                     cfh.Dispose();
+                }
             }
+
             Native.Instance.rocksdb_close(Handle);
         }
 
@@ -168,7 +194,7 @@ public long Get(byte[] key, long keyLength, byte[] buffer, long offset, long len
             }
         }
 
-        public KeyValuePair<byte[],byte[]>[] MultiGet(byte[][] keys, ColumnFamilyHandle[] cf = null, ReadOptions readOptions = null)
+        public KeyValuePair<byte[], byte[]>[] MultiGet(byte[][] keys, ColumnFamilyHandle[] cf = null, ReadOptions readOptions = null)
         {
             return Native.Instance.rocksdb_multi_get(Handle, (readOptions ?? DefaultReadOptions).Handle, keys);
         }
@@ -261,7 +287,7 @@ public void DropColumnFamily(string name)
             Native.Instance.rocksdb_drop_column_family(Handle, cf.Handle);
             columnFamilies.Remove(name);
         }
-        
+
         public ColumnFamilyHandle GetDefaultColumnFamily()
         {
             return GetColumnFamily(ColumnFamilies.DefaultName);

tests/RocksDbSharpTest/LifestyleTest.cs

@@ -0,0 +1,44 @@
+using System;
+using System.IO;
+using RocksDbSharp;
+using Xunit;
+// ReSharper disable RedundantArgumentDefaultValue
+// ReSharper disable ArgumentsStyleLiteral
+
+namespace RocksDbSharpTest
+{
+    public class LifestyleTest
+    {
+        [Fact]
+        public void DoubleDisposableDoesNotThrow()
+        {
+            var testdir = Path.Combine(Path.GetTempPath(), "lifestyle_test");
+            var testdb = Path.Combine(testdir, "main");
+            var path = Environment.ExpandEnvironmentVariables(testdb);
+
+            if (Directory.Exists(testdir))
+            {
+                Directory.Delete(testdir, recursive: true);
+            }
+
+            Directory.CreateDirectory(testdir);
+
+            var options = new DbOptions().SetCreateIfMissing(true).EnableStatistics();
+
+            var db = RocksDb.Open(options, path);
+
+            db.Dispose();
+
+            // throws AccessViolationException, which on my machine crashed the process so hard that XUnit coulnd't cope...
+            //
+            db.Dispose();
+            //
+            // got this in Event Viewer though:
+            //
+            //  Application: dotnet.exe
+            //  CoreCLR Version: 4.6.28619.1
+            //  Description: The process was terminated due to an internal error in the .NET Runtime at IP 00007FFF39BC5AA3 (00007FFF39A20000) with exit code c0000005.
+            //
+        }
+    }
+}