Merge pull request #1438 from libgit2/ethomson/native_load

Native loading: simplify `git_libgit2_init` / `git_libgit2_shutdown`

Author: ethomson

CHANGES.md

@@ -18,6 +18,9 @@
 
 ### Fixes
 
+ - The exception thrown when the native library cannot be loaded is now
+   able to be caught and will no longer crash the process.
+
 ## v0.24 - ([diff](https://github.com/libgit2/libgit2sharp/compare/v0.23..v0.24))
 
 This is the last release before a moving to .NET Core compatible library.

LibGit2Sharp/Core/NativeMethods.cs

@@ -17,62 +17,13 @@ internal static partial class NativeMethods
     {
         public const uint GIT_PATH_MAX = 4096;
         private const string libgit2 = NativeDllName.Name;
-        // This is here to keep the pointer alive
-#pragma warning disable 0414
-        private static readonly LibraryLifetimeObject lifetimeObject;
-#pragma warning restore 0414
-        private static int handlesCount;
-
-        /// <summary>
-        /// Internal hack to ensure that the call to git_threads_shutdown is called after all handle finalizers
-        /// have run to completion ensuring that no dangling git-related finalizer runs after git_threads_shutdown.
-        /// There should never be more than one instance of this object per AppDomain.
-        /// </summary>
-        private sealed class LibraryLifetimeObject
-#if DESKTOP
-            : CriticalFinalizerObject
-#endif
-        {
-            // Ensure mono can JIT the .cctor and adjust the PATH before trying to load the native library.
-            // See https://github.com/libgit2/libgit2sharp/pull/190
-            [MethodImpl(MethodImplOptions.NoInlining)]
-            public LibraryLifetimeObject()
-            {
-                int res = git_libgit2_init();
-                Ensure.Int32Result(res);
-                if (res == 1)
-                {
-                    // Ignore the error that this propagates. Call it in case openssl is being used.
-                    git_openssl_set_locking();
-                }
-                AddHandle();
-            }
-
-            ~LibraryLifetimeObject()
-            {
-                RemoveHandle();
-            }
-        }
-
-#if DESKTOP
-        [ReliabilityContract(Consistency.WillNotCorruptState, Cer.Success)]
-#endif
-        internal static void AddHandle()
-        {
-            Interlocked.Increment(ref handlesCount);
-        }
 
-#if DESKTOP
-        [ReliabilityContract(Consistency.WillNotCorruptState, Cer.Success)]
-#endif
-        internal static void RemoveHandle()
-        {
-            int count = Interlocked.Decrement(ref handlesCount);
-            if (count == 0)
-            {
-                git_libgit2_shutdown();
-            }
-        }
+        // An object tied to the lifecycle of the NativeMethods static class.
+        // This will handle initialization and shutdown of the underlying
+        // native library.
+        #pragma warning disable 0414
+        private static readonly NativeShutdownObject shutdownObject;
+        #pragma warning restore 0414
 
         static NativeMethods()
         {
@@ -87,8 +38,30 @@ static NativeMethods()
                     String.Format(CultureInfo.InvariantCulture, "{0}{1}{2}", path, Path.PathSeparator, Environment.GetEnvironmentVariable(pathEnvVariable)));
             }
 
-            // See LibraryLifetimeObject description.
-            lifetimeObject = new LibraryLifetimeObject();
+            LoadNativeLibrary();
+            shutdownObject = new NativeShutdownObject();
+        }
+
+        // Avoid inlining this method because otherwise mono's JITter may try
+        // to load the library _before_ we've configured the path.
+        [MethodImpl(MethodImplOptions.NoInlining)]
+        private static void LoadNativeLibrary()
+        {
+            // Configure the OpenSSL locking on the true initialization
+            // of the library.
+            if (git_libgit2_init() == 1)
+            {
+                git_openssl_set_locking();
+            }
+        }
+
+        // Shutdown the native library in a finalizer.
+        private sealed class NativeShutdownObject
+        {
+            ~NativeShutdownObject()
+            {
+                git_libgit2_shutdown();
+            }
         }
 
         [DllImport(libgit2)]