On MacOSX lldb needs to be code signed. The Debug, DebugClang and Release builds are set to code sign using a code signing certificate named "lldb_codesign". If you have re-installed a new OS, please delete all old lldb_codesign items from your keychain. There will be 3: a code signing certification and a public and private key. Reboot after deleting them. You will also need to delete and build folders that contained old signed items. The darwin kernel will cache code sigining using the executable's file system node, so you will need to delete the file so the kernel clears its cache. If you don't have one yet you will need to: - Launch /Applications/Utilities/Keychain Access.app - In Keychain Access select the "login" keychain in the "Keychains" list in the upper left hand corner of the window. - Select the following menu item: Keychain Access->Certificate Assistant->Create a Certificate... - Set the following settings Name = lldb_codesign Identity Type = Self Signed Root Certificate Type = Code Signing - Click Create - Click Continue - Click Done - Click on the "My Certificates" - Double click on your new lldb_codesign certificate - Turn down the "Trust" disclosure triangle, scroll to the "Code Signing" trust pulldown menu and select "Always Trust" and authenticate as needed using your username and password. - Drag the new "lldb_codesign" code signing certificate (not the public or private keys of the same name) from the "login" keychain to the "System" keychain in the Keychains pane on the left hand side of the main Keychain Access window. This will move this certificate to the "System" keychain. You'll have to authorize a few more times, set it to be "Always trusted" when asked. - Remove "~/Desktop/lldb_codesign.cer" file on your desktop if there is one. - In the Keychain Access GUI, click and drag "lldb_codesign" in the "System" keychain onto the desktop. The drag will create a "~/Desktop/lldb_codesign.cer" file used in the next step. - Switch to Terminal, and run the following: sudo security add-trust -d -r trustRoot -p basic -p codeSign -k /Library/Keychains/System.keychain ~/Desktop/lldb_codesign.cer rm -f ~/Desktop/lldb_codesign.cer - Drag the "lldb_codesign" certificate from the "System" keychain back into the "login" keychain - Quit Keychain Access - Reboot - Clean by removing all previously creating code signed binaries and rebuild lldb and you should be able to debug. When you build your LLDB for the first time, the Xcode GUI will prompt you for permission to use the "lldb_codesign" keychain. Be sure to click "Always Allow" on your first build. From here on out, the "lldb_codesign" will be trusted and you can build from the command line without having to authorize. Also the first time you debug using a LLDB that was built with this code signing certificate, you will need to authenticate once.