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We receive occasional reports of PuTTY crashing out with
However, we haven't been able to reproduce the problem ourselves.
In recent versions of PuTTY (0.58 and up), the error takes the form of one or more error boxes saying "line==NULL in terminal.c" and giving some diagnostic information, along with an exhortation to contact us.
In versions of PuTTY before snapshot 2005-03-07, the error
is instead a failure of an assertion in
line != NULL (the precise line number has changed
a lot due to the extensive terminal re-engineering since 0.56).
We've had one report since we added diagnostics which indicates that screen doesn't contain enough entries. However, we haven't thought of a plausible mechanism for screen or alt_screen to end up undersized.
(Possibly related, although we've no hard evidence for this: assert-fail-newsavelines.)
There seem to be a lot of reports of this error from people using the serial backend in 0.59, which suggests that it can be a symptom of win-handle-double-free (fixed in 0.60).
In fact, in general, we suspect this is a symptom of some sort of memory corruption to which this assertion is particularly sensitive, rather than evidence of a direct logical error.
line==NULL in terminal.c lineno=5376 y=65 w=182 h=65 count(scrollback=00890758)=2 count(screen=008BE508)=65 count(alt=00890768)=65 alt_sblines=64 whichtree=008BE508 treeindex=65
line==NULL in terminal.c lineno=4754 y=51 w=153 h=56 count(scrollback=003F1BF0)=382 count(screen=003F1C00)=56 count(alt=00B620C8)=56 alt_sblines=0 whichtree=003F1C00 treeindex=51
line==NULL in terminal.c lineno=4754 y=18 w=89 h=47 count(scrollback=011E1AA8)=200 count(screen=011E1AB8)=47 count(alt=011F9BF0)=47 alt_sblines=0 whichtree=011E1AB8 treeindex=18
linux==NULL in terminal.c lineno=4754 y=10 w=80 h=24 count(scrollback=003A1C60)=200 count(screen=003A1C70)=24 count(alt=003A1F90)=24 alt_sblines=0 whichtree=003A1C70 treeindex=10
One user (email@example.com) reported a failure of the same assertion with PuTTY 0.58. However, as their screen is apparently zero rows high (presumably due to their window manager), this pathological case is a problem that's now protected against via zero-rows-cols-crash.
I am using bblean blackbox for windows as a shell on windows XP SP2, and whenever I rollup a maximized putty window the following fatal error results:line==NULL in terminal.c lineno=4621 y=0 w=93 h=0 count(scrollback=003B0F60)=200 count(screen=00CFA2B8)=0 count(alt=003B0F70)=0 alt_sblines=0 whichtree=00CFA2B8 treeindex=0
Perhaps an unrelated bug that's already been fixed: