Bug 688326 - procedure data target not always closed
procedure data target not always closed
Product: Ghostscript
Classification: Unclassified
Component: PS Interpreter
: P3 major
Assigned To: Ray Johnston
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Reported: 2005-10-06 18:39 UTC by Chapman Flack
Modified: 2008-12-19 08:31 UTC (History)
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Description Chapman Flack 2005-10-06 18:39:09 UTC
When a procedure is a data target, it is signalled that it has been closed by
one final callback with a possibly empty string containing any final buffered
data, and the boolean false. GS 8.51 does not seem to do this unless the buffer
is nonempty at time of closefile:

AFPL Ghostscript 8.51 (2005-04-18)
Copyright (C) 2005 artofcode LLC, Benicia, CA.  All rights reserved.
This software comes with NO WARRANTY: see the file PUBLIC for details.
GS>{ =only == ( ) } /NullEncode filter dup (Hi) writestring closefile
false(i)  % good, but:

GS>{ =only == ( ) } /NullEncode filter dup (Hi) writestring
GS<1>dup flushfile closefile
GS>     % whoa, where's the close?   and even:

GS>{ =only == ( ) } /NullEncode filter closefile
GS>     % whoa, where's the close?

By contrast:
PostScript(r) Version 3010.108
(c) Copyright 1984-1999 Adobe Systems Incorporated.
Typefaces (c) Copyright 1981 Linotype-Hell AG and/or its subsidiaries.
All Rights Reserved.
PS>{ =print == ( ) } /NullEncode filter dup (Hi) writestring dup flushfile
false()       % good, gets closed

PS>{ =print == ( ) } /NullEncode filter closefile
false()       % good, gets closed

Not sure when this changed; my code that relies on procedure data
targets worked in GS 7.07, but 8.51 is definitely broken.  The bug
means a data target procedure that needs to take special action on
close fails badly.
Comment 1 Chapman Flack 2005-10-06 19:00:44 UTC
Weird: in CVS diffs for zfproc.c, I don't see anything between 7.07 and 8.51
that looks like it could account for this - but I definitely never saw the
problem before upgrading, and now it's entirely repeatable.
Comment 2 Ray Johnston 2005-11-06 09:40:16 UTC
Performing regression test (on Genoa test suite) with the patch:

*** 279,285 ****
      stream_proc_state *const ss = (stream_proc_state *) st;
      uint rcount = pr->limit - pr->ptr;

!     if (rcount > 0) {
        uint wcount = r_size(&ss->data) - ss->index;
        uint count = min(rcount, wcount);

--- 279,286 ----
      stream_proc_state *const ss = (stream_proc_state *) st;
      uint rcount = pr->limit - pr->ptr;

!     /* if 'last' return CALLC even when rcount == 0. ss->eof terminates */
!     if (rcount > 0 || (last && !ss->eof)) {
        uint wcount = r_size(&ss->data) - ss->index;
        uint count = min(rcount, wcount);


This definitely results in the 'false' call, producing:


and *should* be OK for other proc_write usage. As the PLRM states,
Encode filters are fairly rare, and procedure targets are a subset
of those. I will examine the Genoa tests to see which, if any, of
them tests this case. If no problems, I will commit.
Comment 3 Ray Johnston 2005-11-06 11:21:29 UTC
Patch committed. Testing showed no problems.