MNT: Change objective C code to Automatic Reference Counting (ARC) by greglucas · Pull Request #23060 · matplotlib/matplotlib · GitHub

PR Summary

This updates the objective C macosx backend to use automatic reference counting instead of relying on manual tracking and releasing of the memory. It seems like this is recommended now, but I am definitely not an expert in this.

PR Checklist

Tests and Styling

[N/A] Has pytest style unit tests (and pytest passes).
[N/A] Is Flake 8 compliant (install flake8-docstrings and run flake8 --docstring-convention=all).

Documentation

[N/A] New features are documented, with examples if plot related.
[N/A] New features have an entry in doc/users/next_whats_new/ (follow instructions in README.rst there).
[N/A] API changes documented in doc/api/next_api_changes/ (follow instructions in README.rst there).
[N/A] Documentation is sphinx and numpydoc compliant (the docs should build without error).

The backend seems to continue to function after this. However, I'm not sure how you would like it tested.

I'm not sure it is "testable"... Here is the traceback I was using to make it compatible if I enable ARC on main currently. This was in an effort to trace down the memory leaks.

Here is the ARC recommendation: https://microsoft.github.io/objc-guide/MethodsAndImplementations/AutomaticReferenceCounting.html#convention

expand for traceback

    src/_macosx.m:336:17: error: 'release' is unavailable: not available in automatic reference counting mode
        [self->view release];
                    ^
    /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX12.3.sdk/usr/include/objc/NSObject.h:37:1: note: 'release' has been explicitly marked unavailable here
    - (oneway void)release OBJC_ARC_UNAVAILABLE;
    ^
    src/_macosx.m:336:17: error: ARC forbids explicit message send of 'release'
        [self->view release];
         ~~~~~~~~~~ ^
    src/_macosx.m:344:45: error: cast of Objective-C pointer type 'View *' to C pointer type 'void *' requires a bridged cast
                                   (void*)self, (void*)(self->view));
                                                ^~~~~~~~~~~~~~~~~~~
    src/_macosx.m:344:46: note: use __bridge to convert directly (no change in ownership)
                                   (void*)self, (void*)(self->view));
                                                 ^
                                                 __bridge
    src/_macosx.m:344:52: note: use CFBridgingRetain call to make an ARC object available as a +1 'void *'
                                   (void*)self, (void*)(self->view));
                                                       ^
                                                       CFBridgingRetain
    src/_macosx.m:548:17: error: 'release' is unavailable: not available in automatic reference counting mode
            [window release];
                    ^
    /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX12.3.sdk/usr/include/objc/NSObject.h:37:1: note: 'release' has been explicitly marked unavailable here
    - (oneway void)release OBJC_ARC_UNAVAILABLE;
    ^
    src/_macosx.m:548:17: error: ARC forbids explicit message send of 'release'
            [window release];
             ~~~~~~ ^
    src/_macosx.m:601:46: error: cast of Objective-C pointer type 'Window *' to C pointer type 'void *' requires a bridged cast
                                   (void*) self, (void*)(self->window));
                                                 ^~~~~~~~~~~~~~~~~~~~~
    src/_macosx.m:601:47: note: use __bridge to convert directly (no change in ownership)
                                   (void*) self, (void*)(self->window));
                                                  ^
                                                  __bridge
    src/_macosx.m:601:53: note: use CFBridgingRetain call to make an ARC object available as a +1 'void *'
                                   (void*) self, (void*)(self->window));
                                                        ^
                                                        CFBridgingRetain
    src/_macosx.m:651:81: error: ARC forbids explicit message send of 'autorelease'
            NSImage* image = [[[NSImage alloc] initByReferencingFile: ns_icon_path] autorelease];
                              ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ^
    src/_macosx.m:651:81: error: 'autorelease' is unavailable: not available in automatic reference counting mode
    /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX12.3.sdk/usr/include/objc/NSObject.h:38:1: note: 'autorelease' has been explicitly marked unavailable here
    - (instancetype)autorelease OBJC_ARC_UNAVAILABLE;
    ^
    src/_macosx.m:682:60: error: ARC forbids explicit message send of 'autorelease'
                               encoding: NSUTF8StringEncoding] autorelease];
                               ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ^
    src/_macosx.m:682:60: error: 'autorelease' is unavailable: not available in automatic reference counting mode
    /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX12.3.sdk/usr/include/objc/NSObject.h:38:1: note: 'autorelease' has been explicitly marked unavailable here
    - (instancetype)autorelease OBJC_ARC_UNAVAILABLE;
    ^
    src/_macosx.m:769:67: error: must explicitly describe intended ownership of an object array parameter
    - (void)installCallbacks:(SEL[7])actions forButtons:(NSButton*[7])buttons;
                                                                      ^
    src/_macosx.m:795:67: error: must explicitly describe intended ownership of an object array parameter
    - (void)installCallbacks:(SEL[7])actions forButtons:(NSButton*[7])buttons
                                                                      ^
    src/_macosx.m:790:5: error: the result of a delegate init call must be immediately returned or assigned to 'self'
        [self init];
        ^~~~~~~~~~~
    src/_macosx.m:836:18: error: 'release' is unavailable: not available in automatic reference counting mode
            [handler release];
                     ^
    /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX12.3.sdk/usr/include/objc/NSObject.h:37:1: note: 'release' has been explicitly marked unavailable here
    - (oneway void)release OBJC_ARC_UNAVAILABLE;
    ^
    src/_macosx.m:836:18: error: ARC forbids explicit message send of 'release'
            [handler release];
             ~~~~~~~ ^
    src/_macosx.m:928:21: error: 'release' is unavailable: not available in automatic reference counting mode
            [buttons[i] release];
                        ^
    /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX12.3.sdk/usr/include/objc/NSObject.h:37:1: note: 'release' has been explicitly marked unavailable here
    - (oneway void)release OBJC_ARC_UNAVAILABLE;
    ^
    src/_macosx.m:928:21: error: ARC forbids explicit message send of 'release'
            [buttons[i] release];
             ~~~~~~~~~~ ^
    src/_macosx.m:929:16: error: 'release' is unavailable: not available in automatic reference counting mode
            [image release];
                   ^
    /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX12.3.sdk/usr/include/objc/NSObject.h:37:1: note: 'release' has been explicitly marked unavailable here
    - (oneway void)release OBJC_ARC_UNAVAILABLE;
    ^
    src/_macosx.m:929:16: error: ARC forbids explicit message send of 'release'
            [image release];
             ~~~~~ ^
    fatal error: too many errors emitted, stopping now [-ferror-limit=]
    20 errors generated.
    error: command '/usr/bin/clang' failed with exit code 1

I don't know anything about this, other than that this PR works on my machine and it doesn't appear to do anything malicious. Is there anyone else who ha sufficient macOS experience to vouch for this? Also is ARC sufficiently back compatible?

Also is ARC sufficiently back compatible?

It came in MacOSX 10.7, so it has been around for quite a while now. Note that I did put a check at the top of the file as well so this will throw an error during compile if ARC is not enabled.

marking as merge w/ one review unless another Mac user wants to review I will merge in a week or so...

https://developer.apple.com/documentation/objectivec/nsobject/1571945-allocwithzone

Do not override allocWithZone: to include any initialization code. Instead, class-specific versions of init... methods.

OK, good thing we are deleting it?

it is also not clear we used this as the actual call site just above uses [[super allocWithZone:Null] init] ?

This all came in via 7bacdc5 with the commit message

This patch allows interrupts to be delivered once Python is fixed.

This updates the objective C macosx backend to use automatic reference counting instead of relying on manual tracking and releasing of the memory.

I took the liberty of rebasing and removing the line that was breaking the wheel build.

Please merge this @greglucas if you are happy with the commit I added.

Yes, that commit looks good, it must have come in since the last rebase. Thanks for fixing it!

greglucas added the GUI: MacOSX label May 18, 2022

greglucas added this to the v3.6.0 milestone May 18, 2022

QuLogic added the CI: Run cibuildwheel Run wheel building tests on a PR label May 20, 2022

jklymak approved these changes May 24, 2022

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jklymak added the status: merge with single review? label Jun 23, 2022

tacaswell reviewed Jun 24, 2022

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greglucas and others added 2 commits June 24, 2022 20:08

MNT: Change objective C code to Automatic Reference Counting (ARC)

b46ab89

This updates the objective C macosx backend to use automatic reference counting instead of relying on manual tracking and releasing of the memory.

FIX: remove one more autorelease

ec0a325

tacaswell force-pushed the macosx-ARC branch from c6718ac to ec0a325 Compare June 25, 2022 00:13

tacaswell approved these changes Jun 25, 2022

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greglucas merged commit d2f87e8 into matplotlib:main Jun 26, 2022

greglucas deleted the macosx-ARC branch June 26, 2022 23:53

QuLogic removed the status: merge with single review? label Jun 27, 2022

QuLogic mentioned this pull request Aug 5, 2022

MNT: Clean up some UTF strings and memory autorelease #21756

Closed

6 tasks

greglucas mentioned this pull request Aug 17, 2022

[Bug]: macosx subplot tool causes segfault when window closed #23653

Closed

dstansby mentioned this pull request Jan 2, 2023

[MNT]: Is the macosx backend (very slowly) leaking strings? #21722

Closed

greglucas mentioned this pull request May 30, 2026

Fix several MacOS memory management bugs #31769

Merged

1 task done

iccir mentioned this pull request May 31, 2026

[MNT]: Re-enable Automatic Reference Counting (ARC) for macOS backend. #31797

Closed

MNT: Change objective C code to Automatic Reference Counting (ARC) by greglucas · Pull Request #23060 · matplotlib/matplotlib · GitHub

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MNT: Change objective C code to Automatic Reference Counting (ARC) - #23060

MNT: Change objective C code to Automatic Reference Counting (ARC)#23060
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                   return sharedWindowServerConnectionManager;
               }
-              + (id)allocWithZone:(NSZone *)zone

MNT: Change objective C code to Automatic Reference Counting (ARC) by greglucas · Pull Request #23060 · matplotlib/matplotlib · GitHub

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MNT: Change objective C code to Automatic Reference Counting (ARC) - #23060

MNT: Change objective C code to Automatic Reference Counting (ARC)#23060greglucas merged 2 commits intomatplotlib:mainmatplotlib/matplotlib:mainfrom greglucas:macosx-ARCgreglucas/matplotlib:macosx-ARCCopy head branch name to clipboard

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greglucas commented May 18, 2022

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MNT: Change objective C code to Automatic Reference Counting (ARC)#23060
greglucas merged 2 commits into
matplotlib:mainfrom
greglucas:macosx-ARC