Fix a bug with blocks in ARC mode being incorrectly released.

Test/BlockTest_arc.m

@@ -0,0 +1,17 @@
+#include <stdio.h>
+
+int foo() {
+	__block id x;
+    void (^hello)(void) = ^(void) {
+        printf("hello is running, %p\n", x);
+    };
+    printf("1\n");
+    hello();
+    printf("2\n");
+    hello = 0;    // Here ARC is releasing the block, that's why we don't see '3' printed.
+    printf("3\n");
+    return 0;
+}
+int main() {
+  return foo();
+}

Test/CMakeLists.txt

@@ -7,6 +7,7 @@
 set(TESTS
 	AllocatePair.m
 	BlockImpTest.m
+	BlockTest_arc.m
 	BoxedForeignException.m
 	ExceptionTest.m
 	ForeignException.m
@@ -26,9 +27,13 @@ set(TESTS
 function(addtest_flags TEST FLAGS TEST_SOURCE)
 	add_executable(${TEST} ${TEST_SOURCE})
 	add_test(${TEST} ${TEST})
+	set(ARC "")
+	if (TEST MATCHES ".*_arc")
+		set(ARC "-fobjc-arc")
+	endif()
 	set_target_properties(${TEST} PROPERTIES
 		INCLUDE_DIRECTORIES "${CMAKE_SOURCE_DIR}"
-		COMPILE_FLAGS "-fobjc-runtime=gnustep-1.7 -fblocks ${FLAGS}"
+		COMPILE_FLAGS "-fobjc-runtime=gnustep-1.7 -fblocks ${FLAGS} ${ARC}"
 		LINKER_LANGUAGE C
 	)
 	set_property(TEST ${TEST} PROPERTY

arc.m

@@ -185,6 +185,16 @@ static inline void release(id obj)
 {
 	if (isSmallObject(obj)) { return; }
 	Class cls = obj->isa;
+	if (cls == &_NSConcreteMallocBlock)
+	{
+		_Block_release(obj);
+		return;
+	}
+	if ((cls == &_NSConcreteStackBlock) ||
+	    (cls == &_NSConcreteGlobalBlock))
+	{
+		return;
+	}
 	if (objc_test_class_flag(cls, objc_class_flag_fast_arc))
 	{
 		intptr_t *refCount = ((intptr_t*)obj) - 1;