The preliminary implementation of PANICTRACE on VMS had a "Fixme"
that this fixes, and a "TODO" that this makes moot, but the main reason
for this patch is that vmsmisc.c had been changed to call vms_define(),
which resides in vmsunix.c. Since vmsmisc.obj is linked into progarms
in util/ and vmsunix.obj isn't, enabling PANICTRACE caused linking
problems for those. This moves the code that wants to call vms_define()
into vmsunix.c (despite the fact that it's not even vaguely related to
Unix emulation), so that it only matters to nethack and doesn't impact
the utility programs anymore.
This uses a VMS facility called LIB$INITIALIZE to call code before
main() starts. It's rather messy--at least when written in something
other than assembler or Bliss--and shouldn't be needed for nethack,
but I couldn't figure out how to trap the condition signalled by
lib$signal(SS$_DEBUG) when the debugger isn't available to do so, so I
needed a way to make issuing that signal be conditional upon debugger
availability. One of the arguments passed to LIB$INITIALIZE-invoked
routines contains information that makes if feasible to deduce whether
the debugger is available.
Even when PANICTRACE is disabled, that's useful for handling abort
due to panic while in running in wizard mode.
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