Ghostscript for PS integrity test: terminate at EOF, return error unless stack is empty - testing

Question

To test the integrity of PostScript files, I'd like to run Ghostscript in the following way:
Return 1 (or other error code) on error
Return 0 (success) at EOF if stack is empty
Return 1 (or other error code) otherwise
I could run gs in the background, and use a timeout to force termination if gs hangs with items left on the stack. Is there an easier solution?

Answer 1

Ghostscript won't hang if you send files as input (unless you write a program which enters an infinite loop or otherwise fails to reach a halting state). Having items on any of the stacks won't cause it to hang.
On the other hand, it won't give you an error if a PostScript program leaves operands on the operand stack (or dictionaries on the dictionary stack, clips on the clip stack or gstates on the graphics state stack). This is because that's not an error, and since PostScript interpreters normally run in a job server loop its not a problem either. Terminating the job returns control to the job server loop which does a save and restore round the total job, thereby clearing up anything left behind.
I'd suggest that if you really want to do this you need to adopt the same approach, you need to write a PostScript program which executes the PostScript program you want to 'test', then checks the operand stack (and other stacks if required) to see if anything is left. Note that you will want to execute the test program in a stopped context, as an error in the course of the program will clearly potentially leave stuff lying around.
Ghostscript returns 0 on a clean exit and a value less than 0 for errors, if I remember correctly. You would need to use signalerror in your test framework in order to raise an error if items are left at the end of a program.
[EDIT]
Anything supplied to Ghostscript on the command line by either -s or -d is defined in systemdict, so if we do -sInputFileName=/test.pdf then we will find in systemdict a key /InputFileName whose value is a string with the contents (/test.pdf). We can use that to pass the filename to our program.
The stopped operator takes an executable array as an argument, and returns either true or false depending on whether an error occurred while executing the array (3rd Edition PLRM, p 697).
So we need to run the program contained in the filename we've been given, and do it in a 'stopped' context. Something like this:
{InputFileName run} stopped
{
(Error occurred\n) print flush
%% Potentially check $error for more information.
}{
(program terminated normally\n) print flush
%% Here you could check the various stacks
} ifelse

Answer 2

The following, based 90% on KenS's answer, is 99% satisfactory:
Program checkIntegrity.ps:
{Script run} stopped
{
(\n===> Integrity test failed: ) print Script print ( has error\n\n) print
handleerror
(ignore this error which only serves to force a return value of 1) /syntaxerror signalerror
}{
% script passed, now check the stack
count dup 0 eq {
pop (\n===> Integrity test passed: ) print Script print ( terminated normally\n\n) print
} {
(\n===> Integrity test failed: ) print Script print ( left ) print
3 string cvs print ( item(s) on stack\n\n) print
Script /syntaxerror signalerror
} ifelse
} ifelse
quit
Execute with
gs -q -sScript=CodeToBeChecked.ps checkIntegrity.ps ; echo $?
For the last 1% of satisfaction I would need a replacement for
(blabla) /syntaxerror signalerror
It forces exit with return code 1, but is very verbous and distracts from the actual error in the checked script that is reported by handleerror. Therefore a cleaner way to exit(1) would be welcome.