Re: [Bug-XBoard] Infinite recursion

[h.g. muller]

> However if start xboard in my normal Danish locale the error error does 
> not come up, and the engine setting menu item are enabled. If I click on 
> "Engine #1 settings", xboard will crash.
> ...
> But the point is that the behavoir depends on the locale in a way it 
> shouldn't.

I guess the problem is that XBoard (as described in the protocol specs) 
triggers on receiving a message containing "No such file" from the engine 
process, and that the engine probably sent a translated version of that 
message. That is a bit hard to fix. We could translate the system standard 
error messages it compares to in backend.c. But that is tricky; they really 
would have to be translated to the exact messages that the system in that 
locale would produce. We could of course let XBoard request the messages by 
error number in its own locale, and use those in the comparison. But also 
that will not always do what we need, because you could be running the 
engine on a machine with a different locale as wher XBoard is running.

One problem, which I have just been fixing even before I saw your report on 
this, is that the master version that does this is indeed a bit broken: it 
ignores pipe breaks before engine initialization is complete. While in fact 
detection of EOF while reading from the engine process would have been a 
good alternative method to produce an error popup and trigger the switch 
back to -ncp mode. (It would be a different error popup, "engine exited 
unexpectedly" in stead of "failed to start engine", but I could live with 
that.) This problem came up when starting non-existent UCI engines, as 
Polyglot wraps the error message in a "tellusererror" command, which 
effectively hides it from XBoard, so that the only signal to go on is 
Polyglot exiting.

I have fixed that with the most-recent commit. This should prevent the 
other problem, because it would disable the menu you had to click to cause 
it. I guess it was not so much caused by recursion as well as repetitive 
triggering of the same error condition ('broken pipe'), and failure to make 
that trigger the required action to solve the problem.