Ghostscript 'offending input' - ghostscript

Question

When searching for an occurrence of text in a PostScript file, I receive the following error:
gsapi_run_string_continue returns -21
The API documentation specifies that return codes > 0 are "Error" but doesn't describe it any more specifically. Full error console output below - error occurs twice identically, only one occurrence displayed here.
GPL Ghostscript 9.15 (2014-09-22)
Copyright (C) 2014 Artifex Software, Inc. All rights reserved.
This software comes with NO WARRANTY: see the file PUBLIC for details.
Displaying DSC file C:/Users/c-toothm/Desktop/PRDFlow12_30_2014_050307/1230ouptut.ps
Displaying page 1
%%[ ProductName: GPL Ghostscript ]%%
%%[ LastPage ]%%
Extracting text using pstotext...
Ghostscript returns error code -21`
--- Begin offending input ---
evice /pop , d
initmatrix [1 0 0 1 0 0] concat colspSet`
0.00 43.32 +
0.94 0.95 +S
(XSFT2200041.img) run
EPSFILE2200041 restore
;
0 0 0 sco 5 Lw N 4950 4742 M 4800 4742 I K
0 0 0 sco 5 Lw N 4950 4752 M 4800 4752 I K
0 0 0 sco 5 Lw N 4950 4762 M 4800 476
--- End offending input ---
gsapi_run_string_continue returns -21`
[duplicate error redacted]
Our production output creates a giant .ps file every day and this error occurs in many, but not all, .ps files when searching for text. Randomly selected .ps files from the web do not throw the error, so this GS build seems OK - definitely a problem with my file.
What "offending input" is being referred to here and what can I do to address it?

Answer 1

I'd need to see the PostScript file to tell you exactly what is wrong, but 'evice' is not a PostScript operator and so that is likely the problem. Also, from ghostpdl/gs/psi/ierrors.h error code -21 is e_undefined which means the interpreter has encountered an undefined token, which is some confirmation that this is the problem.
This could be because the file contains a 'typo' like that (perhaps it should be setpagedevice or something), or it could be because a filter is improperly terminated, or has insufficient data, and consumes extra bytes from the input stream, chewing up your program.
You should start by using the Ghostscript executable and reproduce the error with that (you might also try the display device, to see whether the problem is related to pstotext), that will allow you to give a command line which other people can then duplicate. With that, and a copy of the offending file I can tell you exactly what's wrong, without it, not much hope.
Bear in mind that PostScript is an interpreted programming language, so its pretty much impossible to tell you what's wrong with your program without seeing the code.
FWIW you might like to try the Ghostscript txtwrite device instead of pstotext, the device doesn't rely on tinkering with the language like pstotext does. pstotext is also really old (the last release is coming up on its 11th birthday) and unsupported.....