There is a bug in Ghostscript (which I have reported) having do with the printobject and writeobject operators; sometimes arrays output by those operators are output with the wrong offsets, causing them to be read back incorrectly. If you use these operators, then you may wish to patch this
bug. (It is also needed if you are using TeXnicard, or any other software
which uses these operators.)

Instructions for patching it are provided here, but note that I have not
signed the Artifex contribution agreement (but I will tell you that I am willing to release my changes into the public domain and that anyone is
free to apply this patch (subject to the license of Ghostscript), but they might not believe me). This patch is done entirely in PostScript, and does
not require recompiling Ghostscript.

The method of working is to use a temporary dictionary to keep track of
array offeets. The file called Resource/Init/gs_btokn.ps defines the printobject and writeobject operators; change this file as described.

Find the following code:
cntdict /arraytype {
dup dup length 5 -1 roll add 4 2 roll { //.cntobj exec } forall

After the line with "cntdict /arraytype {", insert the line:
dup 3 index 3 bitshift def

This enters the array into a temporary dictionary, together with its
offset in the binary object format.

To set up that temporary dictionary, find the definition of .writeobjects
and add "mark .dicttomark begin" at the beginning, and "end" at the end.

There is then a forall loop for writing the contents of an array by the
use of the .bosobject operator; it starts with "(x\000xxxxxx) .bosobject
dup 1 6 index put". Before the string with the "x"s, add the following:
dup type /arraytype eq {
currentdict 1 index known {3 2 roll pop dup load 3 1 roll} if
} if

That will find the array offset in the temporary dictionary and will set
the offset known to .bosobject to that number.

My tests show that this works, even if there are duplicate objects.

Also, the authors of Ghostscript may wish to fix it in a different way
anyways, possibly by an implementation in a C code.

I also wrote a set of C macros to parse the PostScript binary object
format, which I will post in a separate article. (These C macros are a
part of TeXnicard. The above description of the patch is also included
with TeXnicard, since it is not fixed in the official released version
of Ghostscript yet.)

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