#13447: Make libsingular multivariate polynomial rings collectable
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Reporter: nbruin | Owner: rlm
Type: defect | Status: new
Priority: major | Milestone: sage-5.4
Component: memleak | Resolution:
Keywords: | Work issues:
Report Upstream: N/A | Reviewers:
Authors: | Merged in:
Dependencies: | Stopgaps:
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Comment (by nbruin):
OK, I did a little experiment and tried to build singular with plain
malloc rather than omalloc. In principle, omalloc has an `--with-
emulate...` flag, but the API offered in that mode is woefully incomplete
for singular use. I tried to extend it a little. Very rough result:
[http://sage.math.washington.edu/home/nbruin/singular-3-1-5.malloc.spkg]
One problem is supplying a `memdup`, which needs to know the size of an
allocated block from its pointer. On BSD, you can use `malloc_size` for
that. On linux one could use `malloc_usable_size`. The rest is a whole
swath of routines that need to be supplied.
The package above is very dirty, but on bsd.math it did provide me with an
apparently working libsingular. The singular executable produced didn't
seem usable, so keep your old one!
The doctest passes! Not exactly what we were hoping for, but it does make
a double-free unlikely. That would have been detected. Corruption after
freeing could still be possible, since `malloc` allocates way bigger
blocks, so freelist data is likely missed.
There is of course also the possibility of some routine writing out of
bounds, which is less likely to trigger problems with malloc too.
Singular people might be interested in incorporating the changes to
omalloc (and preferrably extend them a little bit) so that `--with-
emulate...` becomes a viable option for Singular debugging. Then you can
valgrind singular code.
--
Ticket URL: <http://trac.sagemath.org/sage_trac/ticket/13447#comment:3>
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