LightRider on the forums reports:
"...clicking on the link multiple times creates multiple instances of the bitcoin process, but the user cannot see any affects of them starting. I didn't notice until I checked process explorer and noticed them running. Also, when the client is not running, clicking the link creates a process but no gui appears at all, neither the window nor the tray icon."
<pre> Upgraded -> Started bitcoin -> Tried donation links which failed -> Quit bitcoin -> Found multiple donation link processes and force closed them -> Tried starting bitcoin again, but would get no gui or unresponsive gui -> Tried your suggestion and got same result -> Reboot machine -> bitcoin works fine </pre>
I'm not sure if it's a code bug this time, perhaps it takes too long to pass an URI to the message queue, which makes users impatient. And they click again and again, which can screw things up (which IS not good).
Maybe do a check at startup so the client don't start more instances if it's already running? But Bitcoin-qt 0.7.1 does know that the database is locked and quits after the error message is shown in my windows 7 64-bit.
There seem to be way too many problems with boost::interprocess... how do other programs deal with this? Sending a message to a running program should be something trivial, in my opinion. Maybe it would require platform-specific code for almost any platform, but that isn't worse than what we have now.
Qt supports named pipes on any platform that we care about, imo that's the best solution.
Platform specific solutions are more work and probably require hacking around qt left and right for window handles and such.
@burger2 There is a check at startup, which just tries to send new URIs to the message queue used for handling URIs. If that succeeds skip further client startup and exit, if no message queue is available start a new client. To me it seems that check doesn't work reliable, when impatient users are clicking to fast on a bitcoin: URI (which is indeed no fault and should not crash the client though).
I wasn't impatiently clicking on the link multiple times in rapid succession. I clicked it twice, the second time only after a few minutes. Rebooting the computer did seem to resolve the issue though, so it might have just been a specific issue to my machine. As I suggested, maybe rebooting a windows machine after upgrading should be recommended.
I was not trying to say you are that kind of impatient user, I just wanted to clarify this can trigger a problem :).
@gavinandresen As your paymentserver pull was merged, this can be closed IMO.