On Sun, Apr 15, 2012 at 13:50, Tom Browder <[email protected]> wrote:
> On Sun, Apr 15, 2012 at 08:34, Christopher Sean Morrison <[email protected]>
> wrote:
> ...
>> There are certainly places and situations where a bomb
>> might not be caught (such as during the 'catch' or outside the try/catch).
I've found one possible cause of the problem. In
db_tree.s:db_free_tree there is a comment and line:
/*
* Before recursion, smash the magic number, so that if another
* thread tries to free this same tree, they will fail.
*/
tp->magic = (uint32_t)-3; /* special bad flag */
and that "special bad flag" looks suspiciously like the
"Unknown_Magic" number I see in the crash message:
ERROR: bad pointer 0x812390: s/b union tree(x91191191),
was Unknown_Magic(xfffffffd),
file /usr/src/tbrowde/brlcad-svn/brlcad/trunk/src/librt/db_tree.c, line 1458
That occurs when trying to free a tree in a catch block. When I
commented out the delete tree line in g-nff the crash stopped and we
got a graceful end.
A few questions:
1. Shouldn't the special flag be generalized and get a bu macro?
2. Shouldn't a test for the "free flag" be built into the
db_free_tree function to return silently if the tree is already freed?
3. Is there a way to force single-threading for debugging?
I've checked the other culprits in the TODO list I added and the same
kind of situation is happening. I made a local change to db_tree to
add the test I mentioned in question 2 above and the bomb problems
went away (except for g-iges which now has another problem but with
another bad tree magic number [maybe other "special" flags floating
around?]).
I also got a successful full regression test afterwards. Obviously
the test has wide-spread ramifications so it may not be the right
thing to do, but it looks promising.
Best regards,
-Tom
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