Mac Terminal – ‘pointer being freed was not allocated’ error when opening terminal

It looks like you don’t have the right permissions on the /usr/bin directory.

Solution for OS X 10.11 (El Capitan) and later:

1. Install Onyx 3.1.3 app (Free analog of Disk Utility)
2. Choose ‘Maintenance’ -> ‘Permissions’ -> ‘Execute’.
   

Solution for older versions of OS X:

• Open ‘Disk Utility’ app -> Press ‘Repair Disk Permissions’.

It will set default permissions for the /usr/bin directory.
If this step doesn’t help try this:

• Delete com.apple.terminal.plist from the ~/Library/Preferences folder;