[tlbuild] dvi test?

[John Hawkinson]

Nice one, Dick!

I wrote this morning, on Mon, 31 Jan 2022 at 08:05:56 EST in <YffetKpDl7plua+V at louder-room.local>:

> This suggests to me that the complicated code around
> make_backup_fp(), globals.dvi_file.bak_fp, and duplicate file
> descriptors and soforth is involved, and I don't really understand
> what is going on with all that.
...
> I spent quite a while last night before going to bed trying to
> figure out why we are messing around with fd 6, which has not been
> opened recently, at least not by try_fopen(). It looks loke it's a
> mkstemp() -style temprorary file from the aforementioned backup fd
> stuff.


And indeed, looks like that triggered a lightbulb for Dick; Richard Koch <koch at uoregon.edu> wrote on Mon, 31 Jan 2022
at 15:35:47 EST in <441A24A9-6D9E-4BD4-8BD1-692DEA6EC792 at uoregon.edu>:

> I just tried
> 
> 	xdvi -notempfile koch.dvi
> 
> with this file. Now R works and the file does not crash. Does this solve the problem on other dvi files?

Yes! Adding "-notempfile" solves the problem for the original t2a.dvi, as well as for test-dick.dvi (from Bruno) and koch.dvi (from Dick).
Apparently I have not kept up with xdvi's expansive featureset and missed the feature that this disabled. I probably should have reviewed the man page. Here's what it has to say:

       Before displaying a page of a DVI file, xdvi will check to see
       if the file has changed since the last time it was displayed.
       If this is the case, it will reload the file.  This feature
       allows you to preview many versions of the same file while
       running xdvi only once. Since it cannot read partial DVI files,
       xdvik versions starting from 22.74.3 will create a temporary
       copy of the DVI file being viewed, to ensure that the file can
       be viewed without interruptions. (The -notempfile can be used
       to turn off this feature).

I'm happy there is a workaround now. And also hopefully this will help us in debugging.

--
jhawk at alum.mit.edu
John Hawkinson