Thanks to all of you
The  CFRelease(imageRef); was the problem and the  CFRelease(subImageRef); is OK
My fault was then to apply the old days « Create rule » , bypassing ARC ! 
I was misled by Instruments/Leaks which  reports a leak, which meant to me that 
I had to look  for  a missing release, not an over-release !! 
Very confusing !

Thank again 
Happy Dog Days ( 41°C  / 105,8°F here ! ) 

JP



> Le 24 août 2023 à 00:55, Rob Petrovec <petr...@mac.com> a écrit :
> 
> CGImageForProposedRect returns an autoreleased CGImageRef, so your 
> CFRelease(imageRef) is an overrelease and likely the cause of your problem.  
> The rest of the code looks fine, including the release of subImageRef (if it 
> was uncommented).
> 
> —Rob
> 
> Le 24 août 2023 à 01:11, Alex Zavatone <z...@mac.com> a écrit :
> 
> Got a small sample we could play with?  I would expect the crash on explicit 
> release as it would cause a double release.
> 
> I tend to ignore I strums to with leaks and use the Memory Graph debugger 
> religiously.
> 
> If you have a little sample showing this, I would be happy to test a bit with 
> it.
> 
> Cheers,
> Alex Zavatone


Le 24 août 2023 à 07:44, Sandor Szatmari <admin.szatmari....@gmail.com> a écrit 
:

You mention ARC… aren’t you not supposed to explicitly release objects under 
ARC?  Am I misunderstanding?

Sandor

> 
>> On Aug 23, 2023, at 4:47 PM, JPH via Cocoa-dev <cocoa-dev@lists.apple.com> 
>> wrote:
>> 
>> Hello friends,
>> 
>> The enclosed procedure is producing a NSImage from  another NSImage, by 
>> cropping in a NSRect.
>> The resulting sub-Image feeds  an imageView  in the APP Interface and the 
>> may change frequently,  then being hopefully disposed by ARC
>> The last line of the procedure :
>> NSImage *subImage = [[NSImage alloc] initWithCGImage:subImageRef 
>> size:NSZeroSize];
>> Generates a leak problem.
>> 
>> it is quite unclear if i should release or not  the  subImageRef.
>> 
>> If I release,          the app crashes soon after.
>> If I don’t release, Instrument/Leaks reports a leak  of subImageRef  after 
>> each call.
>> 
>> Obviously, ARC never releases    subImageRef    which, as far as I 
>> understand, is owned by the  subImage after the call.
>> 
>> Digging the web , apple doc, and various AI, did not provide a solution to 
>> this dilemme.
>> 
>> I would greatly appreciate some help on this
>> 
>> Happy summer.. 
>> JP
>> 
>> C
>> //=============================================================================
>> + (NSImage *)getSubImageFromImage:(NSImage *)image atRect:(NSRect)rect
>> //=============================================================================
>> {
>> // Convert the NSImage to a CGImageRef
>> CGImageRef imageRef= nil, subImageRef= nil;
>> imageRef = [image CGImageForProposedRect:NULL context:nil hints:nil];
>> if (imageRef == nil ) {  return nil; } // Failed to create CGImageRef
>> // Get the subimage from the CGImageRef
>> subImageRef = CGImageCreateWithImageInRect(imageRef, rect);
>> CFRelease(imageRef);
>> if(subImageRef == nil ) {  return nil;  }  // Failed to create subImageRef
>> // Convert the subimage CGImageRef to an NSImage
>> NSImage *subImage = [[NSImage alloc] initWithCGImage:subImageRef 
>> size:NSZeroSize];
>> //   CFRelease(subImageRef); // it is quite unclear if i should release the  
>> subImageRef
>> //If I release, the app crashes soon after.
>> // If i dont release Instrument/Leaks report a leak at next call.
>> // The subImage goes to a NSbutton in the interface, and will also soon be 
>> replaced by another one, producing a leak of subImageRef
>> 
>> return subImage;
>> }// getSubImageFromImage
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