Entering debugger: Cannot create Swift scratch context (couldn't create a ClangImporter)

similiar to

which do not resolve this issue that I am encountering

Description of problem


I am seeing an error which prevents using lldb debugger on Swift code/projects. It is seen on any Swift or SwiftUI project that I've tried. This is the error displayed in lldb console when first breakpoint is encountered:

Code Block
Cannot create Swift scratch context (couldn't create a ClangImporter)(lldb) 

  • Xcode Version 12.3 (12C33)

  • macOS Big Sur

    • Intel

    • M1

Troubleshooting


I originally thought this was also working on an Intel Mac running Big Sur/Xcode 12.3, but was mistaken. Using my customized shell environment on the following setups, I encounter the same couldn't create a ClangImporter.

  1. M1 Mac mini, main account (an "Admin" account)

  2. same M1 Mac mini, new "dev" account (an "Admin" account)

  3. Intel MBP, main account

They are all using an Intel Homebrew install, and my customized shell environment if that provides a clue?

I captured some lldb debugging info by putting expr types in ~/.lldbinit but the outputs were basically identical (when discounting scratch file paaths and memory addresses) compared to the "working clean" account log (described below)

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log enable -f /tmp/lldb-log.txt lldb expr types


works in a "clean" user account


I created a new, uncustomized "Standard" testuser account on the M1 Mac mini, and launched the same system Xcode.app. There was no longer this error message, and was able to inspect variables at a swift program breakpoint in Swift context, including po symbol.

Impact


Effectively this makes the debugger in Swift on Xcode projects on my systems essentially unable to inspect Swift contexts' state.



  • This problem appeared during development in a new account which was created after the problem appeared in the original development account without any changes to the shell, which is bash (both default and running as shown by ps -o comm= $$ and echo $SHELL)

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Accepted Reply

After hours and days of attempting to narrow down the cause, after I remove all zsh customizations (in dotfiles) on an account, the LLDB Swift debugging finally works again. Swift structure state can be inspected, and po symbol works.

(the lldb startup error Cannot create Swift scratch context (couldn't create a ClangImporter) is gone too)

I haven't isolated the specific root cause of why this is, but that is the general case.
  • where it is dotfiles.

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Replies

After hours and days of attempting to narrow down the cause, after I remove all zsh customizations (in dotfiles) on an account, the LLDB Swift debugging finally works again. Swift structure state can be inspected, and po symbol works.

(the lldb startup error Cannot create Swift scratch context (couldn't create a ClangImporter) is gone too)

I haven't isolated the specific root cause of why this is, but that is the general case.
  • where it is dotfiles.

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I isolated it finally to a very very old (mid-1990s) csh-backed shell utility that was being used to add PATH components.

I replaced its functionality with ZSH's built-in way to do this, and everything seems to be working as it should be.

It's not completely clear what exactly was breaking the LLDB invocation by Xcode, but I am fine with modified way.


Code Block shell
# put at end of path
path+=/new/path
# put at front of path
path=(/first/path $path)


Hey @idcrook ive tried removing all my .zsh files in my home directory but still getting the same issue. Where exactly did you find your csh-backed shell utility? was that in your homre directory?
@idcrook thanks for your post! I ended up changing my shell from zsh to bash and the debugger started to work again.
  • Please let me know, how to change from Zsh to bash?

  • This problem appeared during Swift development of an iOS app using a new account with default shell set to bash (after the problem appeared in the main dev account) , so the shell is not the whole story. Tried restarting Xcode (v 12.3 running on Catalina) - no change.

  • The problem then disappeared and debugger started working again ...

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