In OSX, the default log name is incorrect.
In the "Perforce Settings" window, in the tab "Diagnostics + Utilities” the default log file name is "~/Desktop\p4connect.log". That “\” comes from expecting a Windows system; it creates a file named “Desktop\p4connect.log” at the top level of the user directory rather than a “p4connect.log" in the “Desktop" directory.
Additionally, the default location for the log file should be in ~/Library/Logs/.