#13447: Make libsingular multivariate polynomial rings collectable
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Reporter: nbruin |
Owner:
Type: defect |
Status: needs_info
Priority: major |
Milestone: sage-5.4
Component: memleak |
Resolution:
Keywords: | Work
issues: Input from a libsingular expert
Report Upstream: None of the above - read trac for reasoning. |
Reviewers: Simon King
Authors: Nils Bruin, Simon King | Merged
in:
Dependencies: #11521 |
Stopgaps:
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Comment (by SimonKing):
Replying to [comment:51 nbruin]:
> I'm not so sure that
> {{{#!python
> currRingHdl = enterid("my_awesome_sage_ring", 0, RING_CMD, &IDROOT,
1)
> currRingHdl.data.uring.ref += 1
> }}}
> is entirely safe.
I am sure that it is not safe: One can't even call singular_ring_delete on
it. That's why I removed it, unless `currRing==NULL`.
> '''EDIT:''' `kernel/Number.h` contains uncommented definitions:
> {{{#!C++
> using namespace boost;
> inline void intrusive_ptr_add_ref(ring r){
> r->ref++;
> //Print("ref count after add: %d", r->ref);
> }
> inline void intrusive_ptr_release(ring r){
> if (r->ref<=0) rDelete(r);
> else {
> r->ref--;
>
> }
> //Print("ref count after release: %d", r->ref);
> }
> }}}
> I find the `ptr_release` a little worrisome: Do the singular people
believe that `r->ref ==0` means that there is still a reference?
According to the code snipped, the ring is deleted if `r->ref==0`. So,
apparently `r->ref==0` means that there is ''no'' reference.
> this code all indicates that special action is required only if `ref<=0`
'before' decreasing.
If `ref<=0` then no reference is left, hence, the ring is deleted.
Otherwise, the reference counter is decremented. I really don't understand
the problem.
> In that case we should probably ensure that `singular_ring_ref` and
`singular_delete_ring` are somehow aliased to
`boost::intrusive_ptr_add_ref` and `intrusive_ptr_release` from
`kernel/Number.h`.
Singular tests whether `ref<=0`; if it is, then the ring is deleted, but
if it isn't then the counter is decremented.
We first decrement the counter, and then test whether `ref<0`; if it is,
then the ring is deleted, but if it isn't then no further action is taken.
Isn't that logically the same?
--
Ticket URL: <http://trac.sagemath.org/sage_trac/ticket/13447#comment:53>
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