[metapost] Uninitialized variable sometimes causing malformed TFM files

[Marcel Krüger]

 ---- On Wed, 20 Mar 2019 21:13:52 +0100 luigi scarso <luigi.scarso at gmail.com> wrote ----
 > 
 > 
 > On Wed, Mar 20, 2019 at 6:29 PM luigi scarso <luigi.scarso at gmail.com> wrote:
 >  sorry for delay, I will it asap. -- 
 > luigi
 > 
 > latest mpost from texlive
> 
> # cat test.mp
> input mfplain;mode:=localfont;input cmr10.mf;

> # mpost test.mp 
> This is MetaPost, version 2.00 (TeX Live 2019/dev) (kpathsea version 6.3.1/dev)
> (/opt/luatex/texlive/2018/texmf-dist/metapost/base/mpost.mp
> (/opt/luatex/texlive/2018/texmf-dist/metapost/base/plain.mp
> Preloading the plain mem file, version 1.005) ) (./test.mp
> (/opt/luatex/texlive/2018/texmf-dist/metapost/base/mfplain.mp
> Preloading the plain base, version 0.99: preliminaries,
>  basic constants and mathematical macros,
>  macros for converting units,
> ! Inconsistent equation (off by 2.77794).
> <to be read again> 
>                    ;
> l.230 mm*bpppix_=2.83464;
>                                pt*bpppix_=0.99626;
> ? 

That's the expected behaviour, mfplain defines the units without `#` as 50 times their actual values in `bp`
to simulate pixels with density `50dots/bp~3600dpi`. `plain` does not have to use such tricks, so their `mm`
are completely different. If you do not load plain everything works fine as long as you do not change the numbersystem:

% mfplain '\mode:=localfont;input cmr10.mf'
This is MetaPost, version 2.00 (TeX Live 2018) (kpathsea version 6.3.0)
(/usr/local/texlive/2018/texmf-dist/metapost/base/mfplain.mp
Preloading the plain base, version 0.99: preliminaries,
 basic constants and mathematical macros,
[...]
Font metrics written on cmr10.tfm.
128 output files written: cmr10.0 .. cmr10.127
Transcript written on cmr10.log.