#13731: Fix libsingular memory management
---------------------------+------------------------------------------------
Reporter: nbruin | Owner: rlm
Type: defect | Status: new
Priority: major | Milestone: sage-5.6
Component: memleak | Resolution:
Keywords: | Work issues:
Report Upstream: N/A | Reviewers:
Authors: | Merged in:
Dependencies: | Stopgaps:
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Comment (by nbruin):
> It's not immediately clear to me that `ExpSize/sizeof(long)` really is
(at most) `rN+1` (see `p_MemAdd.h` for the definition).
In fact, it certainly is not:
{{{
int
ExpSize=(((rN+1)*sizeof(int)+sizeof(long)-1)/sizeof(long))*sizeof(long);
}}}
so `ExpSize` gets rounded ''up''. If `sizeof(int)=4` and `sizeof(long)=8`
then for `rN=2` we get `(rN+1)*sizeof(int)=12` and `ExpSize=16` (which, by
the valgrind report, is probably exactly the case we're in). So
`p_MemAdd_LengthGeneral` is definitely writing out of bounds. I think this
code should simply read:
{{{
int *F=(int *)omAlloc0(ExpSize);
int *G=(int *)omAlloc0(ExpSize);
memcpy(F, F0,ExpSize);
// pExpVectorCopy(F,F0);
memcpy(G, G0,ExpSize);
}}}
God knows why they add an array of int as an array of long in
{{{
p_MemAdd_LengthGeneral(F, G, ExpSize/sizeof(long));
}}}
Are they sure there's no carry (I guess, if these are non-negative signed
ints the sign bit would buffer any carry).
Is it viable to simply ditch Singular :-?
By the way, since most architectures with `sizeof(long)=8` would be 8-byte
aligned anyway, I doubt that this error would ever lead to real trouble.
But the sloppiness surely is worrying.
--
Ticket URL: <http://trac.sagemath.org/sage_trac/ticket/13731#comment:31>
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