segfault and onCleanup()

[John W. Eaton]

On  7-Dec-2011, Rik wrote:

| On 12/07/2011 12:41 PM, John W. Eaton wrote:
| > I'm not seeing this crash, but I checked in this change as a temporary
| > fix for those of you who are.
| >
| > I don't know that I'll be able to debug this problem unless I can
| > find a way to reproduce it myself.
| 
| I've single-stepped through the segfault.  The trouble is not directly in
| cleanup_instance().  Rather the code 'delete instance;' triggers the 
destructor
| for the class.  The destructor defined in ov-typeinfo.h is empty, but there 
are
| a number of Array objects in the class and the destructor for the Array class
| is called.  It is not the first element of the Array object which triggers the
| segfault.  It seems to be the 14th but I don't know if that is the 14th 
element
| of the Array or the 14th Array object.  It also might simply be a red 
herring. 
| The relevant part of the trace is below.
| 
| #18 0x00002aaaad757460 in _int_free (av=0x7fffffffd1f0, p=0x0) at 
malloc.c:5017
| #19 0x00002aaaab1059cb in ~octave_value (this=0x63ce70, __in_chrg=<value
| optimized out>) at ov.h:311
| #20 0x00002aaaab106c8f in ~ArrayRep (this=0x63ce70, __in_chrg=<value optimized
| out>) at ../liboctave/Array.h:94
| #21 0x00002aaaab106321 in ~Array (this=0x62cfe8, __in_chrg=<value optimized
| out>) at ../liboctave/Array.h:235
| #22 0x00002aaaab5b3582 in ~octave_value_typeinfo (this=0x62cfc0, __in_chrg=
| <value optimized out>) at ov-typeinfo.h:192
| #23 0x00002aaaab5b3f67 in octave_value_typeinfo::cleanup_instance () at
| ov-typeinfo.h:223
| #24 0x00002aaaac3ea2c8 in ~singleton_cleanup_list (this=0x612380, __in_chrg=
| <value optimized out>) at singleton-cleanup.cc:39
| #25 0x00002aaaab4c02a1 in singleton_cleanup_list::cleanup () at ../liboctave/
| singleton-cleanup.h:26
| #26 0x00002aaaab4bd280 in clean_up_and_exit (retval=0) at toplev.cc:697
| #27 0x00002aaaab46f5d1 in octave_main (argc=11, argv=0x7fffffffd1f8, embedded=
| 0) at octave.cc:904
| #28 0x0000000000400769 in main (argc=11, argv=0x7fffffffd1f8) at main.c:35
| 
| Also, most of the time I can start 'run-octave' and mess around in the
| interpreter without problems.  However, it is always reproducible with 'make
| check'.  I did some verification with runtests and the following functions
| always cause a segfault when exiting octave if I have used 'test XXX'.
| 
| ./linear-algebra/onenormest.m
| ./geometry/griddata3.m
| ./geometry/delaunay.m
| ./plot/trisurf.m
| ./plot/triplot.m
| ./plot/trimesh.m
| ./sparse/svds.m
| ../src/DLD-FUNCTIONS/onCleanup.cc
| 
| The common element (clue?) is that they all use onCleanup within a %!test
| block.  If I comment out the onCleanup () call then the segfault disappears. 
| Actually, on further trolling through the code, these are the only points 
where
| onCleanup is ever used.  I did a quick test with the following in the file
| blah.m
| 
| function blah ()
|   restore_state = onCleanup (@() disp ("hello"));
|   disp ("First");
| endfunction
| 
| Calling blah() correctly displays
| First
| hello
| 
| but this segfaults as well when I exit Octave.  This problem isn't confined to
| some weirdness of %!test blocks.
| 
| I'm of the opinion that the whole onCleanup class is broken.  Perhaps you can
| see quickly what is wrong.  Otherwise, the %!test blocks can be rewritten to
| use unwind_protect blocks to accomplish the same task of restoring the random
| seed.

I don't see anything really wrong with onCleanup except that it is
dynamically loaded.  So I checked in a change to build it into
liboctinterp so that clearing it should not be able to cause trouble.

I also checked in some changes for gh_manager and reactivated all the
singleton cleanup_instance functions.  As part of the gh_manager
changes, errors in closerequestfcn callback functions should be
handled better than I think they were before.

You'll need to be sure to remove the obsolete onCleanup.oct file
from your build directory.

I'm not seeing any crashes now.  I've run make check multiple times and
also ran through all the plot demos without seeing Octave crashing
when it exits.

If you see failures, please let me know what OS (32 or 64 bit?),
compiler version, etc. that you are using so I can try to duplicate
the problems you are seeing.

jwe