NSThread: Implement +detatchThreadWithBlock: and -initWithBlock: (#454)

* NSThread: Implement +detatchThreadWithBlock: and -initWithBlock:

* Remove extraneous include

* NSThread: Define GSThreadBlock so that GCC stub impl does not fail

* Add missing spaces - trivial style fixup

---------

Co-authored-by: rfm <richardfrithmacdonald@gmail.com>

Headers/Foundation/NSThread.h

@@ -43,6 +43,11 @@
 extern "C" {
 #endif
 
+#if OS_API_VERSION(MAC_OS_X_VERSION_10_12, GS_API_LATEST)
+#import <GNUstepBase/GSBlocks.h>
+DEFINE_BLOCK_TYPE_NO_ARGS(GSThreadBlock, void);
+#endif  
+
 /**
  * This class encapsulates OpenStep threading.  See [NSLock] and its
  * subclasses for handling synchronisation between threads.<br />
@@ -67,6 +72,7 @@ GS_EXPORT_CLASS
   BOOL			_cancelled;
   BOOL			_active;
   BOOL			_finished;
+  BOOL			_targetIsBlock;
   NSHandler		*_exception_handler;    // Not retained.
   NSMutableDictionary	*_thread_dictionary;
   struct autorelease_thread_vars _autorelease_vars;
@@ -398,6 +404,29 @@ GS_EXPORT void GSUnregisterCurrentThread (void);
 
 #endif
 
+/**
+ * This category contains convenience
+ * initialisers and methods for executing
+ * blocks in different threads and creating
+ * NSThread objects with a block as entry point.
+ */
+@interface NSThread (BlockAdditions)
+
+#if OS_API_VERSION(MAC_OS_X_VERSION_10_12, GS_API_LATEST)
+/**
+ * Detaches a new thread with block as its entry point.
+ */
++ (void) detachNewThreadWithBlock: (GSThreadBlock)block;
+
+/**
+ * Initialises a NSThread object with block as the
+ * entry point.
+ */
+- (instancetype) initWithBlock: (GSThreadBlock)block;
+#endif // OS_API_VERSION
+
+@end
+
 /*
  * Notification Strings.
  * NSBecomingMultiThreaded and NSThreadExiting are defined for strict

Source/NSThread.m

@@ -1337,7 +1337,15 @@ unregisterActiveThread(NSThread *thread)
         NSStringFromSelector(_cmd)];
     }
 
-  [_target performSelector: _selector withObject: _arg];
+  if (_targetIsBlock)
+    {
+      GSThreadBlock block = (GSThreadBlock)_target;
+      CALL_BLOCK_NO_ARGS(block);
+    }
+  else
+    {
+      [_target performSelector: _selector withObject: _arg];
+    }
 }
 
 - (NSString*) name
@@ -2414,6 +2422,31 @@ GSRunLoopInfoForThread(NSThread *aThread)
 
 @end
 
+@implementation NSThread (BlockAdditions)
+
++ (void) detachNewThreadWithBlock: (GSThreadBlock)block
+{
+  NSThread	*thread;
+
+  thread = [[NSThread alloc] initWithBlock: block];
+  [thread start];
+
+  RELEASE(thread);
+}
+
+- (instancetype) initWithBlock: (GSThreadBlock)block
+{
+  if (nil != (self = [self init]))
+    {
+      _targetIsBlock = YES;
+      /* Copy block to heap */
+      _target = _Block_copy(block);
+    } 
+  return self;
+}
+
+@end
+
 /**
  * <p>
  *   This function is provided to let threads started by some other