This bug re-opens: 3137165 metapost fails with MiKTeX 2.9 on Win 7 - there definitly is a problem
bug 3273553 Problem with label in Metapost, may be related.
compiling metapost file eg1.mp (attached file) fails with
tex: The memory dump file could not be found.
tex: Data: tex.fmt
fatal: Command failed: tex --parse-first-line --interaction=nonstopmode mp455818.tex; see mpxerr.log
the eg1.log file (see test1.tar.gz)
This is MetaPost, version 1.211 (MiKTeX 2.9) (MiKTeX 2.9) (mem=mpost 2011.09.07) 8 SEP 2011 13:53
! Unable to make mpx file.
$a$ etex, .5[z0,z1]);
The two files given above are one of your source files
to note about eg1.mp, it uses
plain tex (not latex)
i.e. a simple use of metapost with tex.
in fact the expected eps file is eg1.1.ps (also attached) has been renamed from eg1.1 (in attached test6.zip)
the associated eg1.log and mpxerr files have been included in test1.tar.gz.
running the tex file through (test2.tar.gz)
produces a good result when run through dvitomp etc
(see the associated makefile attached for all the commands run to generate test results)
similarly running the same example eg1.mp through MiKTeX 2.7 processes the file without error
to cut a long story short (for a full description of the series of tests see the makefile)
I observed the following:
MiKTex 2.9 sets an environment variable when invoking the tex (or latex) command. The
environment variable is set in the spawned process the setting is:
There is no documentation available about what this could be for. However,
MiKTeX 2.7 does not set this environment variable.
when this environment variable is set (see testtex.bat) and tex is run from the command line
to process the a tex file as in test2. It fails with the same error as
that reported here (test5.tar.gz).
setting up allternative batch files:
with a simple command
i.e. unsetting the environment variable and running metapost with these
mpost -tex mptex eg1.mp
now metapost works like it should.