[metapost] decimal: The impossible/a segfault happened

Dan Luecking dluecking at sbcglobal.net
Tue Apr 22 20:12:40 CEST 2014

On Tue Apr 22, 2014, at 01:38:31 CEST Samuel Bronson <naesten at 
gmail.com> wrote:

>I've discovered a way to get either:
>   1. a "! This can't happen (token)." error (MetaPost 1.803 from Debian)
>   2. a segfault (MetaPost ~1.999 from SVN r2007)

Confirmed also for:

Windows 7 with: MetaPost, version 1.803 from Tex Live 2013
as well as with MetaPost, version 1.901 from Tex Live 2014.

In both cases I get a notification from Windows saying:
    "mpost.exe has stopped working"

The posted Input.mp is the dangerous bend sign from manfnt.mf.
Years ago I converted this to normal metapost syntax in a file
dbend.mp and that works fine with both versions.

Removing "labels(38);" from Input.mp allows it to work.
But keeping that labels command, I get the same Windows
message even if I remove all other commands in beginchar
except a definition of z38.

It would seem labels() invokes some problematic code,
at least in versions 1.803 and 1.901.


Daniel H. Luecking
Department of Mathematical Sciences
Fayetteville, Arkansas

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