Fix crashes with flint 3.3

[antonio-rojas]

In flint 3.3, gr_mat_struct replaced the rows array with row stride [1], update hmod_mat_struct accordingly.

Also, in that case we can use upstream's nmod_mat_entry macro, which doesn't do any type checking.

Fixes #86

[1] flintlib/flint@25251b8

[JohnCremona]

Thanks for finding and fixing this. I have been away and will check it out tomorrow

[JohnCremona]

When I build eclib using this patch and flint-3.3 I get a segfault in tests/smattest1, specifically in line 1393 of libsrc/mat.cc.
mod_mat_entry(A,i,j) = (uscalar)posmod(M(i+1,j+1),ipr);
in the function mod_mat_from_mat() which creates a FLINT matrix from an eclib matrix. I don't know why this happens on my laptop when the checks on github pass.

NB smattest1 has scalar=32-bit int.

[antonio-rojas]

When I build eclib using this patch and flint-3.3 I get a segfault in tests/smattest1, specifically in line 1393 of libsrc/mat.cc. mod_mat_entry(A,i,j) = (uscalar)posmod(M(i+1,j+1),ipr); in the function mod_mat_from_mat() which creates a FLINT matrix from an eclib matrix. I don't know why this happens on my laptop when the checks on github pass.

NB smattest1 has scalar=32-bit int.

That's the crash I get without patching and that this PR is supposed to fix - so it looks like some other code path needs to be fixed too. I can't reproduce it locally though, all tests pass for me.

[JohnCremona]

Thankss for the quick response. Let me check what I am doing after 12 days of holiday...

[JohnCremona]

I cannot understand what is happening. The code in flinterface.h was written by Fredrik and relies on knowledge of FLINT internals which I do not have, and which have changed. But the mystery is why it works for you and for github but not for me (ubuntu 24.04.2 LTS, gcc 13.3.0).

--OK I now see that despite rebuilding from scratch, the executables in tests/ are being linked with an older flint lib (/usr/local/lib/libflint.so.18) not the newly installed one /usr/local/lib/libflint.so.21.0.0. I don't know why, I did make distclean and ./configure after installing the new flint system-wide.

[JohnCremona]

Now when I rebuild eclib after putting --with-flint=/usr/local on the ./configure line, it works fine though ldd shows that the executables are still linked to the old libflint.so.18. So this is better but I am still not actually testing the new eclib code with the new flint. I will try deleting the older libflint completely and building again.

[JohnCremona]

All OK, sorry about the noise.