[2017-10] Only null check target for delegate if method is not static. (#7476)

* Only null check target for delegate if method is not static. Fixes regression introduced by 1cfd52452a4af3fd6eee32f45a8067926af8479e.

* pass first stack arg to transform, so we get the correct delegate wrapper

the wrapper logic detects if the target method of a delegate is a static
method with an argument bound, and handles it properly in the generated
code.

fixes mono/tests/delegate14.cs

5 files changed, 31 insertions, 7 deletions

diff --git a/mono/mini/interp/interp-internals.h b/mono/mini/interp/interp-internals.h
index 894747e23d0..5cfed578253 100644
--- a/mono/mini/interp/interp-internals.h
+++ b/mono/mini/interp/interp-internals.h
@@ -137,7 +137,7 @@ extern int mono_interp_traceopt;
 extern GSList *jit_classes;
 
 MonoException *
-mono_interp_transform_method (InterpMethod *imethod, ThreadContext *context);
+mono_interp_transform_method (InterpMethod *imethod, ThreadContext *context, MonoDelegate *del);
 
 void
 mono_interp_transform_init (void);
diff --git a/mono/mini/interp/interp.c b/mono/mini/interp/interp.c
index d4a876c2cf6..d742f6539d8 100644
--- a/mono/mini/interp/interp.c
+++ b/mono/mini/interp/interp.c
@@ -1972,7 +1972,7 @@ do_transform_method (InterpFrame *frame, ThreadContext *context)
 	/* Use the parent frame as the current frame is not complete yet */
 	interp_push_lmf (&ext, frame->parent);
 
-	frame->ex = mono_interp_transform_method (frame->imethod, context);
+	frame->ex = mono_interp_transform_method (frame->imethod, context, (MonoDelegate *) frame->stack_args [0].data.p);
 	context->managed_code = 1;
 
 	interp_pop_lmf (&ext);
@@ -2456,7 +2456,7 @@ ves_exec_method_with_context (InterpFrame *frame, ThreadContext *context, unsign
 
 			if (!new_method->transformed) {
 				frame->ip = ip;
-				frame->ex = mono_interp_transform_method (new_method, context);
+				frame->ex = mono_interp_transform_method (new_method, context, NULL);
 				if (frame->ex)
 					goto exit_frame;
 			}
diff --git a/mono/mini/interp/transform.c b/mono/mini/interp/transform.c
index 0bdb1580534..804235194f6 100644
--- a/mono/mini/interp/transform.c
+++ b/mono/mini/interp/transform.c
@@ -4261,7 +4261,7 @@ mono_interp_transform_init (void)
 }
 
 MonoException *
-mono_interp_transform_method (InterpMethod *imethod, ThreadContext *context)
+mono_interp_transform_method (InterpMethod *imethod, ThreadContext *context, MonoDelegate *del)
 {
 	MonoError error;
 	int i, align, size, offset;
@@ -4340,7 +4340,7 @@ mono_interp_transform_method (InterpMethod *imethod, ThreadContext *context)
 					char *wrapper_name = g_strdup_printf ("__icall_wrapper_%s", mi->name);
 					nm = mono_marshal_get_icall_wrapper (mi->sig, wrapper_name, mi->func, TRUE);
 				} else if (*name == 'I' && (strcmp (name, "Invoke") == 0)) {
-					nm = mono_marshal_get_delegate_invoke (method, NULL);
+					nm = mono_marshal_get_delegate_invoke (method, del);
 				} else if (*name == 'B' && (strcmp (name, "BeginInvoke") == 0)) {
 					nm = mono_marshal_get_delegate_begin_invoke (method);
 				} else if (*name == 'E' && (strcmp (name, "EndInvoke") == 0)) {
diff --git a/mono/mini/method-to-ir.c b/mono/mini/method-to-ir.c
index 3185a203fe8..f2808cdfd3b 100644
--- a/mono/mini/method-to-ir.c
+++ b/mono/mini/method-to-ir.c
@@ -3973,8 +3973,10 @@ handle_delegate_ctor (MonoCompile *cfg, MonoClass *klass, MonoInst *target, Mono
 	/* Set target field */
 	/* Optimize away setting of NULL target */
 	if (!MONO_INS_IS_PCONST_NULL (target)) {
-		MONO_EMIT_NEW_BIALU_IMM (cfg, OP_COMPARE_IMM, -1, target->dreg, 0);
-		MONO_EMIT_NEW_COND_EXC (cfg, EQ, "NullReferenceException");
+		if (!(method->flags & METHOD_ATTRIBUTE_STATIC)) {
+			MONO_EMIT_NEW_BIALU_IMM (cfg, OP_COMPARE_IMM, -1, target->dreg, 0);
+			MONO_EMIT_NEW_COND_EXC (cfg, EQ, "NullReferenceException");
+		}
 		MONO_EMIT_NEW_STORE_MEMBASE (cfg, OP_STORE_MEMBASE_REG, obj->dreg, MONO_STRUCT_OFFSET (MonoDelegate, target), target->dreg);
 		if (cfg->gen_write_barriers) {
 			dreg = alloc_preg (cfg);
diff --git a/mono/tests/delegate14.cs b/mono/tests/delegate14.cs
index 2fd7d62b1fa..36c6f896e8a 100644
--- a/mono/tests/delegate14.cs
+++ b/mono/tests/delegate14.cs
@@ -6,6 +6,12 @@ public static class Program
 {
 	public static int Main (string[] args)
 	{
+		// calling delegate on extension method with null target is allowed
+		Func<int> func = null;
+		if (CallFunc(func.CallFuncIfNotNull) != 0)
+			return 2;
+
+		// constructing delegate on instance method with null target should throw
 		ITest obj = null;
 		try
 		{
@@ -23,4 +29,20 @@ public static class Program
 	{
 		void Func ();
 	}
+
+	static int CallFunc(Func<int> func)
+	{
+		return func();
+	}
 }
+
+public static class FuncExtensions
+{
+	public static int CallFuncIfNotNull(this Func<int> func)
+	{
+		if (func != null)
+			return func();
+
+		return 0;
+	}
+}
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