On MacOSX lldb needs to be code signed. The Debug and Release builds are set to code sign using a code signing certificate named lldb_codesign. 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 Change: When using this certificate: Always Trust - Enter your login password to confirm and make it trusted The next steps are necessary on SnowLeopard, but are probably because of a bug how Keychain Access makes certificates. [Note: These also apply for Lion.] - Option-drag the new lldb_codesign certificate from the login keychain to the System keychain in the Keychains pane of the main Keychain Access window to make a copy of this certificate in the System keychain. You'll have to authorize a few more times, set it to be "Always trusted" when asked. - Switch to the System keychain, and drag the copy of lldb_codesign you just made there onto the desktop. - 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 - Right click on the "lldb_codesign" certificate in the "System" keychain (NOT "login", but the one in "System"), and select "Delete" to delete it from the "System" keychain. - Reboot - Clean and rebuild lldb and you should be able to debug. That should do it.