Reapply "Implement NSDate as a small object (tagged pointer) - clang/libobjc2 only (#451)" because of GUI breakage: apps hang when loading NSMenu

This reverts commit cac43f7bfc.

ChangeLog

@@ -15,7 +15,22 @@
 	* Source/NSFileManager.m: Create an NSError object when we fail to
 	copy because the destination item already exists.
 
-2024-09-23: Hugo Melder <hugo@algoriddim.com>
+2024-10-10: Hugo Melder <hugo@algoriddim.com>
+
+	* Source/NSDate.m:
+	* Source/NSDatePrivate.h:
+	NSDate is now a small object in slot 6, when configuring GNUstep with the
+	clang/libobjc2 toolchain.  This is done by compressing the binary64 fp
+	holding the seconds since reference date (because someone at Apple thought
+	it would be a good idea to represent a time interval as a fp). Note that
+	this assumes that IEEE 754 is used.
+	* Source/NSCalendarDate.m:
+	Remove access to the NSDate private concrete Class
+	and implement -timeIntervalSinceReferenceDate instead.
+	Previously, all methods of the concrete date class were
+	added to NSCalendarDate via GSObjCAddClassBehavior.
+
+2024-23-09: Hugo Melder <hugo@algoriddim.com>
 
 	* Headers/Foundation/NSThread.h:
 	* Source/NSString.m:

Source/NSCalendarDate.m

@@ -58,9 +58,6 @@
 @class	GSAbsTimeZone;
 @interface	GSAbsTimeZone : NSObject	// Help the compiler
 @end
-@class	NSGDate;
-@interface	NSGDate : NSObject	// Help the compiler
-@end
 
 
 #define DISTANT_FUTURE	63113990400.0
@@ -396,7 +393,6 @@ GSPrivateTimeNow(void)
       absAbrIMP = (NSString* (*)(id,SEL,id))
 	[absClass instanceMethodForSelector: abrSEL];
 
-      GSObjCAddClassBehavior(self, [NSGDate class]);
       [pool release];
     }
 }
@@ -463,6 +459,11 @@ GSPrivateTimeNow(void)
   return AUTORELEASE(d);
 }
 
+- (NSTimeInterval) timeIntervalSinceReferenceDate
+{
+  return _seconds_since_ref;
+}
+
 /**
  * Creates and returns a new NSCalendarDate object by taking the
  * value of the receiver and adding the interval in seconds specified.

Source/NSDatePrivate.h

@@ -0,0 +1,41 @@
+/** NSDate Private Interface
+   Copyright (C) 2024 Free Software Foundation, Inc.
+
+   Written by: Hugo Melder <hugo@algoriddim.com>
+
+   This file is part of the GNUstep Base Library.
+
+   This library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2 of the License, or (at your option) any later version.
+
+   This library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with this library; if not, write to the Free
+   Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
+   Boston, MA 02110 USA.
+*/
+
+#import <Foundation/NSDate.h>
+
+#if defined(OBJC_SMALL_OBJECT_SHIFT) && (OBJC_SMALL_OBJECT_SHIFT == 3)
+#define USE_SMALL_DATE 1
+#define DATE_CONCRETE_CLASS_NAME GSSmallDate
+#else
+#define USE_SMALL_DATE 0
+#define DATE_CONCRETE_CLASS_NAME NSGDate
+#endif
+
+@interface DATE_CONCRETE_CLASS_NAME : NSDate
+#if USE_SMALL_DATE == 0
+{
+@public
+  NSTimeInterval _seconds_since_ref;
+}
+#endif
+@end

Source/NSTimer.m

@@ -35,9 +35,8 @@
 #import "Foundation/NSRunLoop.h"
 #import "Foundation/NSInvocation.h"
 
-@class	NSGDate;
+#import "NSDatePrivate.h"
-@interface NSGDate : NSObject	// Help the compiler
+
-@end
 static Class	NSDate_class;
 
 /**
@@ -58,7 +57,7 @@ static Class	NSDate_class;
 {
   if (self == [NSTimer class])
     {
-      NSDate_class = [NSGDate class];
+      NSDate_class = [DATE_CONCRETE_CLASS_NAME class];
     }
 }
 

Tests/base/NSFileManager/general.m

@@ -12,7 +12,7 @@
 #ifdef  EQ
 #undef  EQ
 #endif
-#define EPSILON (FLT_EPSILON*100)
+#define EPSILON (DBL_EPSILON*100)
 #define EQ(x,y) ((x >= y - EPSILON) && (x <= y + EPSILON))
 
 @interface      MyHandler : NSObject
@@ -204,6 +204,7 @@ int main()
   NSTimeInterval        ot, nt;
   ot = [[oa fileCreationDate] timeIntervalSinceReferenceDate];
   nt = [[na fileCreationDate] timeIntervalSinceReferenceDate];
+  NSLog(@"ot = %f, nt = %f", ot, nt);
   PASS(EQ(ot, nt), "copy creation date equals original")
   ot = [[oa fileModificationDate] timeIntervalSinceReferenceDate];
   nt = [[na fileModificationDate] timeIntervalSinceReferenceDate];