PuTTY bug defaults-launchable

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When PuTTY loads a saved session, it will under some circumstances automatically launch it if it's launchable. "Launchable" used to simply mean that it actually specified a host name to connect to, but due to the serial port backend it's now a more complex criterion.

The original intention of the PuTTY configuration storage was that "Default Settings" should never describe a session which is launchable, which is why we don't permit a host name to be saved in the default settings. (People occasionally complain about this.)

However, due to an oversight, it is now possible to have Default Settings describe a launchable session: simply set "Protocol" to "Serial", and have the "Serial line" box non-blank (as it is by default). This leads to undesirable behaviour; in particular, PuTTY launched with no arguments will try to start up a session instead of bringing up the configuration dialog.

I'm not sure how best to fix this. Restricting what can be stored in Default Settings so that even serial-based defaults are forced not to be launchable seems to me like the wrong answer. Perhaps the right answer is actually to go through the code and ensure that Default Settings in particular is never automatically launched even if launchable. If we do that, then perhaps we could also repeal the restriction on having a default host name saved in Default Settings.

SGT, 2007-02-10: Should now be fixed, by the method described above: Default Settings may describe a launchable session but is never actually launched unless PuTTY is sure the user really meant it. In particular, merely starting PuTTY doesn't launch the session described by DS, and neither does double-clicking DS from the saved sessions menu. Hitting Open once you've loaded it still works, and using "-load" still works. Also, as mentioned above, I've relaxed the restriction on storing a host name in DS, on the basis that since one type of launchable session is now permitted in DS there's no reason not to permit the other too.

If you get into this situation, and can't upgrade permanently to 0.60 or later, the following workarounds are available:

• Download 0.60, which does not suffer from this problem. You will then be able to edit Default Settings so that PuTTY 0.59 does not attempt to launch a serial connection. (Although if you're using the serial backend, you are likely to need to carry on using 0.60 or later in any case, as the serial support is prone to crashes.)
• If you're happy editing the Registry:
  1. Run REGEDIT.EXE.
  2. Go to HKEY_CURRENT_USER\Software\SimonTatham\PuTTY\Sessions\Default%20Settings
  3. Change the value of the 'Protocol' key from 'serial' to 'ssh'.
• If you don't mind losing all your saved sessions, you can use putty -cleanup. See the documentation.

Audit trail for this bug.