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Re: [cjk] [mailman] texlive svn write access Fw: Re: revisiting ttf2tfm

From: Hin-Tak Leung
Subject: Re: [cjk] [mailman] texlive svn write access Fw: Re: revisiting ttf2tfm and dvipdfmx
Date: Thu, 18 Jul 2013 14:39:06 +0100
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:20.0) Gecko/20100101 Firefox/20.0 SeaMonkey/2.17.1

Peter Breitenlohner wrote:
On Thu, 18 Jul 2013, Hin-Tak Leung wrote:

The command line is simply:
ttf2tfm wcl-01.ttf -P 3 -E 4 -q -w   address@hidden@

but didn't mention that the same font caused indeterminism!


I did, in the same e-mail where the above first appear, further down - here it
is, again, in full - Note "The two fonts mentioned above, ...":

OK, I have just tested this. Running ttf2tfm (FreeType 1) three times in
exactly the same way gave identical results for subfonts 01-54 and a
segfault for subfont 55.  Doing the same with a copy of ttf2tfm in a
different directory gave different .tfm files.  Converting them to .pl files
shows why that is so: the TFM header contains the command line, including
the relative or absolute path to ttf2tfm and they may differ.  Removing
header bytes >=18 from the .pl files gives identical results.


By indeterminism, I did not mean the outcome differs from 10 years ago, but
that the outcome differ between two recent and consecutive runs separated by not more than a few hours or days. I have a 10-year-old script which I
am adding new fonts to, and as a side-effect of adding new font entries,
every font old and new get processed again, and the tfm files shows up differently, since all the generated files now sit on top of git. the old public version - cjk/doc/pdfhowto/examples/gen-map.pl have only about 90 font instance entry, more than half of that open or public fonts - the first 50 or so entries are publicly available fonts - at least at a time in the past. e.g. the Taiwanese government [the 7-11th fonts on that list] now provide a completely different set of 4-5 fonts, more interesting and varied type-face wise than the old, but I don't see those old fonts posted any more.
(the script I have has 460 entries and still growing).

In case it is important, fedora has some sort of system-wide security feature whose name I forgot, controlled by the environment variable MALLOC_PERTURB_ which you can look it up on. I don't know if your system has that. As far as I remember the feature initialises uninitialized memory differently each time a binary is launched (and can be switched off by unsetting MALLOC_PERTURB_ if it proves bothersome). If the indeterminism disappears if I switchs that off, all it says is that ttf2tfm is writing some uninit'ed memory to output files, and therefore does random things when this feature is on. Since ttf2tfm is not supposed to write uninit'ed memory to output (very few programs are supposed to!), I am not going to look into that possibility; but it might help you tracking the indeterminism down if that's important and you can find equivalent dev aids.

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