How can I troubleshoot Xcode Illegal Instruction: 4 error?

Question

I am running Xcode 12.5.1 on Big Sur 11.6 I have been building apps with Xcode for more than four years. Lately I have one app that all too frequently throws the following error:

Illegal Instruction: 4

I am using Swift with UIKit and a combination of Storyboards, Xibs and programmatic code.

I have searched extensively for a solution and have seen this stackoverflow post more than once in my quest. The most popular response is dated and this problem only happens on one specific app. I have reinstalled Xcode, I have rebooted, re-cloned the repository and cleaned the build folder until it is spotless. Co-workers do not experience the issue with the same repository.

How can I troubleshoot the root cause of this annoying error?

Answer 1

It may be the currently opened project file, the new version of Xcode has been run, and you are using the old version of Xcode to open。

like: current project file is running well on Xcode 13.4.1, but if your using Xcode 13.0 to open, then will be show "Illegal Instruction: 4".

please make sure using the same Xcode or New version

Answer 2

Try setting the compilation mode to Whole Module Compilation.

Answer 3

I found the answer in the most unlikely of places. A co-worker pointed me to this post.