Getting GDB to work on Mac OS X Mojave

How to get GDB to work on MacOSX Mojave

Starting from Mac OS X 10.5 (Leopard), Apple starts to lock down the system further and debuggers like GDB now have to be code signed. There is a great article describing steps to get it to work. However, there are a lot of conflicting information on the web and people are having trouble with some of those instructions, myself included. So I’d like to document what I did to get it to work, and highlight the issues I ran into:

On a high-level you need to perform these steps:

  1. You need to create a certificate in System Keychain that is self-sign and always trust for code signing
  2. Sign the GDB binary with the certificate. Include proper entitlements if you are on 10.14+.
  3. Reboot

The article has detailed steps on these steps so I’m not going to repeat them.

A few gotchas that I ran into myself:

  1. If you see this error complaining about code signing even though you had signed the GDB executable:
Starting program: /Users/yzha/github/mysql-server/debug/runtime_output_directory/mysqld
Unable to find Mach task port for process-id 55009: (os/kern) failure (0x5).
 (please check gdb is codesigned - see taskgated(8))

Double check if you had the proper entitlements in a XML file and pass to codesign when you are signing GDB. Many articles on the web in fact didn’t have the entitlement step as it likely is a new requirement 10.14+.

  1. If you are seeing this error even if you had signed with proper entitlements:
During startup program terminated with signal ?, Unknown signal.

or this:

/Users/yizhang/github/leveldb/debug/db_test": not in executable format: file format not recognized

Make sure you stay off GDB 8.2! Upgrade to 8.3 (available in Homebrew already) or downgrade to 8.0.

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