Memory leak with custom style

Nobody has claimed this yet.

Setup the Xcode project for XcodeClangFormat for debugging.
Build the app and set the style to https://github.com/blender/blender/blob/master/.clang-format
Run Extension this time and Xcode launches. Wait for the debugger to attach to the extension.
New Xcode command line tool project of C++ language.
In the C++ file, select all, paste the code given in the summary. [1] it's total 18 lines.
Editor > clang format > format entire file. It will format it correctly.
Select all again, paste the code still in your clipboard.
Editor > clang format > format entire file. It will fail & the original Xcode instance shows memory increase that settles around 500 MB. The trace appears in the console [2] & UI looks like this [3].

[1] Code to copy

//
//  main.cpp
//  clang-format-test
//
//  Copyright © 2020 ak. All rights reserved.
//

#include <iostream>
#include "main.hh"

int main(int argc, const char *argv[])
{
  // Long comment that must be broken down in multiple lines.
  // insert code here... insert code here... insert code here... insert code here... insert code here... insert code here...
  std::cout << "Hello, World!\n";
  return 0;
}

[2] Trace in console

2020-08-03 00:39:49.395275+0530 clang-format[6941:258937] [User Defaults] Couldn't read values in CFPrefsPlistSource<0x60b000012c00> (Domain: XcodeClangFormat, User: kCFPreferencesAnyUser, ByHost: Yes, Container: (null), Contents Need Refresh: Yes): Using kCFPreferencesAnyUser with a container is only allowed for System Containers, detaching from cfprefsd
2020-08-03 00:40:00.626852+0530 clang-format[6941:258937] [general] <NSXPCConnection: 0x60d000017bb0> connection from pid 6924: Warning: Exception caught during invocation of received message, dropping incoming message and invalidating the connection.
Exception: *** -[__NSArrayM objectAtIndex:]: index 18 beyond bounds [0 .. 17]
*** -[__NSArrayM objectAtIndex:]: index 18 beyond bounds [0 .. 17]
(
	0   CoreFoundation                      0x00007fff46876a7d __exceptionPreprocess + 256
	1   libobjc.A.dylib                     0x00007fff70f4ba17 objc_exception_throw + 48
	2   CoreFoundation                      0x00007fff468b5a74 -[CFPrefsConfigurationFileSource initWithConfigurationPropertyList:containingPreferences:] + 0
	3   CoreFoundation                      0x00007fff467b21de -[CFPrefsSearchListSource addNamedVolatileSourceForIdentifier:] + 0
	4   clang-format                        0x0000000105a5ce7b -[ClangFormatCommand performCommandWithInvocation:completionHandler:] + 9099
	5   XcodeKit                            0x000000010ae192f4 -[_XCSourceEditorService performCommandInvocation:commandIdentifier:request:reply:] + 494
	6   Foundation                          0x00007fff48a8da0b __NSXPCCONNECTION_IS_CALLING_OUT_TO_EXPORTED_OBJECT_S4__ + 12
	7   Foundation                          0x00007fff48a3298f -[NSXPCConnection _decodeAndInvokeMessageWithEvent:flags:] + 2499
	8   Foundation                          0x00007fff48a31d63 message_handler + 215
	9   libxpc.dylib                        0x00007fff7294df08 _xpc_connection_call_event_handler + 56
	10  libxpc.dylib                        0x00007fff7294be9e _xpc_connection_mach_event + 933
	11  libdispatch.dylib                   0x00007fff726cc6dd _dispatch_client_callout4 + 9
	12  libdispatch.dylib                   0x00007fff726e10d6 _dispatch_mach_msg_invoke + 436
	13  libdispatch.dylib                   0x00007fff726d2792 _dispatch_lane_serial_drain + 268
	14  libdispatch.dylib                   0x00007fff726e1c19 _dispatch_mach_invoke + 481
	15  libdispatch.dylib                   0x00007fff726d2792 _dispatch_lane_serial_drain + 268
	16  libdispatch.dylib                   0x00007fff726d33c6 _dispatch_lane_invoke + 433
	17  libdispatch.dylib                   0x00007fff726db6ed _dispatch_workloop_worker_thread + 598
	18  libsystem_pthread.dylib             0x00007fff7290c611 _pthread_wqthread + 421
	19  libsystem_pthread.dylib             0x00007fff7290c3fd start_wqthread + 13
)

[3] UI looks like

Screenshot 2020-08-03

Reproduce the failure in the XcodeClangFormat project using the Blender .clang-format style and the 18-line C++ example, then inspect the Extension path and the ClangFormatCommand entry point named in the trace. Done means formatting the file a second time no longer fails, the extension does not accumulate roughly 500 MB, and the XPC connection remains usable.

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