XCode 10.2.1 crashes while trying to open (xcode quits unexpectedly while using the libMainThreadChecker.dylib plug-in)

Question

When I try to open Xcode, it crashes unexpectedly and asks me to reopen. But reopening also gives me the same error. I have XCode 10.2.1 as well as XCode 11.7 installed.

Problem details and system configuration:

Process:               Xcode [1607]
Path:                  /Applications/Xcode1.app/Contents/MacOS/Xcode
Identifier:            com.apple.dt.Xcode
Version:               10.2.1 (14490.122)
Build Info:            IDEFrameworks-14490122000000000~6 (10E1001)
Code Type:             X86-64 (Native)
Parent Process:        ??? [1]
Responsible:           Xcode [1607]
User ID:               501

PlugIn Path:             /Applications/Xcode1.app/Contents/Developer/usr/lib/libMainThreadChecker.dylib
PlugIn Identifier:       libMainThreadChecker.dylib
PlugIn Version:          ??? (64490.34)

Date/Time:             2020-11-16 21:23:39.623 -0500
OS Version:            macOS 11.0.1 (20B29)
Report Version:        12
Bridge OS Version:     5.0.1 (18P2561)
Anonymous UUID:        14ACF447-0D96-DDDB-DD2C-2FE0B3DB664D


Time Awake Since Boot: 4800 seconds

System Integrity Protection: enabled

Crashed Thread:        0  Dispatch queue: com.apple.main-thread

Exception Type:        EXC_BAD_ACCESS (SIGBUS)
Exception Codes:       KERN_PROTECTION_FAILURE at 0x00007fff237919b9
Exception Note:        EXC_CORPSE_NOTIFY

Termination Signal:    Bus error: 10
Termination Reason:    Namespace SIGNAL, Code 0xa
Terminating Process:   exc handler [1607]

VM Regions Near 0x7fff237919b9:
    __TEXT                   7fff22bf8000-7fff23600000 [ 10.0M] r-x/r-x SM=COW  /System/Library/Frameworks/AppKit.framework/Versions/C/AppKit
--> __TEXT                   7fff23600000-7fff23800000 [ 2048K] r-x/rwx SM=COW  /System/Library/Frameworks/AppKit.framework/Versions/C/AppKit
    Submap                   7fff23800000-7fff40000000 [456.0M] r--/rwx SM=PRV  process-only VM submap

Application-Specific Information:
/Applications/Xcode1.app/Contents/Developer/usr/lib/libMainThreadChecker.dylib
ProductBuildVersion: 10E1001

Answer 1

This is a known issues

Currently there is one workaround for this.

You've to run the following command in the Terminal app to avoid crashes when starting Xcode:

defaults write com.apple.dt.Xcode DVTDisableMainThreadChecker 1

Now deactivate "Main Thread Checker" in your Xcode project: Edit Scheme -> Run/Test -> Diagnostics -> Uncheck Main Thread Checker.

Answer 2

Faced the same issue on Big Sur update. Git stopped working as well. Fixed it by running following command in terminal.

defaults write com.apple.dt.Xcode DVTDisableMainThreadChecker 1

Original Answer Reference: https://developer.apple.com/forums/thread/651985?answerId=637934022#637934022

Answer 3

Faced the same issue after updating to Big Sur. Found a temporary workaround:

1. Go to Xcode10.app/Contents/Developer/usr/lib
2. Rename the file libMainThreadChecker.dylib into anything else (I named it _libMainThreadChecker.dylib)

NOTE: If your project has "Main thread checker enabled" it may crash somewhere, so it's better to disable it.