Still memory leaks with matrix operations over GF(2)

[gh-cbe90]

According to the ticket #26349, the bug should have been fixed in Release 9.1, but the provided code

n = 8
X = zero_vector(GF(2), n)
M = zero_matrix(GF(2), n, n)

for _ in range(10000000):
    Y = M * X

still leaks memory (using Ubuntu 18.04.4 LTS). There is no error message when trying to execute, but the memory consumption increases until the process crashes.

[tscrim]

I can confirm that the leak is there. I remember checking when reviewing #26349 and did not see the leak.

[tscrim]

It is something specific to a matrix times a vector. I don't see the leak if I do Y = M * M.

[tscrim]

Okay, here is the problem:

        c._init(self._nrows, VS)
        c._entries = mzd_init(1, self._nrows)

The c._init already allocates c._entries. So this does a double allocation, and so the old allocation from c._init is the leak.

[tscrim]

Here is the fix (plus one local micro-optimization).

---

New commits:

​c050f63

Fixing a memory leak in mat * vec over GF(2).

[tscrim]

Green patchbot.

[chapoton]

ok, but I am no expert.

[tscrim]

Thank you.