Build warnings from GCC on Python 3.12

[stefan6419846]

Re-generating the Cython code on Python 3.12 and running the build afterwards yields some build warnings:

  gcc -fno-strict-overflow -Wsign-compare -DNDEBUG -g -O3 -Wall -fPIC -I/opt/hostedtoolcache/Python/3.12.0/x64/include/python3.12 -c intbitset/intbitset.c -o build/temp.linux-x86_64-cpython-312/intbitset/intbitset.o
  intbitset/intbitset.c: In function ‘__pyx_pf_9intbitset_9intbitset___cinit__’:
  intbitset/intbitset.c:4246:13: warning: ‘PyObject_AsReadBuffer’ is deprecated [-Wdeprecated-declarations]
   4246 |             __pyx_t_4 = (PyObject_AsReadBuffer(__pyx_v_tmp, (&__pyx_v_buf), (&__pyx_v_size)) < 0);
        |             ^~~~~~~~~
  In file included from /opt/hostedtoolcache/Python/3.12.0/x64/include/python3.12/Python.h:100,
                   from intbitset/intbitset.c:16:
  /opt/hostedtoolcache/Python/3.12.0/x64/include/python3.12/abstract.h:369:17: note: declared here
    369 | PyAPI_FUNC(int) PyObject_AsReadBuffer(PyObject *obj,
        |                 ^~~~~~~~~~~~~~~~~~~~~
  intbitset/intbitset.c: In function ‘__pyx_f_9intbitset_9intbitset_fastload’:
  intbitset/intbitset.c:12305:7: warning: ‘PyObject_AsReadBuffer’ is deprecated [-Wdeprecated-declarations]
  12305 |       __pyx_t_9 = (PyObject_AsReadBuffer(__pyx_v_tmp, (&__pyx_v_buf), (&__pyx_v_size)) < 0);
        |       ^~~~~~~~~
  In file included from /opt/hostedtoolcache/Python/3.12.0/x64/include/python3.12/Python.h:100,
                   from intbitset/intbitset.c:16:
  /opt/hostedtoolcache/Python/3.12.0/x64/include/python3.12/abstract.h:369:17: note: declared here
    369 | PyAPI_FUNC(int) PyObject_AsReadBuffer(PyObject *obj,
        |                 ^~~~~~~~~~~~~~~~~~~~~
  gcc -fno-strict-overflow -Wsign-compare -DNDEBUG -g -O3 -Wall -fPIC -I/opt/hostedtoolcache/Python/3.12.0/x64/include/python3.12 -c intbitset/intbitset_impl.c -o build/temp.linux-x86_64-cpython-312/intbitset/intbitset_impl.o
  intbitset/intbitset_impl.c: In function ‘intBitSetResize’:
  intbitset/intbitset_impl.c:178:19: warning: comparison of integer expressions of different signedness: ‘unsigned int’ and ‘int’ [-Wsign-compare]
    178 |     if (allocated > bitset->allocated) {
        |                   ^
  intbitset/intbitset_impl.c: In function ‘intBitSetIsInElem’:
  intbitset/intbitset_impl.c:190:19: warning: comparison of integer expressions of different signedness: ‘unsigned int’ and ‘int’ [-Wsign-compare]
    190 |     return ((elem < bitset->allocated * wordbitsize) ?
        |                   ^
  intbitset/intbitset_impl.c: In function ‘intBitSetAddElem’:
  intbitset/intbitset_impl.c:195:14: warning: comparison of integer expressions of different signedness: ‘unsigned int’ and ‘int’ [-Wsign-compare]
    195 |     if (elem >= (bitset->allocated - 1) * wordbitsize) {
        |              ^~
  intbitset/intbitset_impl.c: In function ‘intBitSetDelElem’:
  intbitset/intbitset_impl.c:207:14: warning: comparison of integer expressions of different signedness: ‘unsigned int’ and ‘int’ [-Wsign-compare]
    207 |     if (elem >= (bitset->allocated - 1) * wordbitsize) {
        |              ^~
  intbitset/intbitset_impl.c: In function ‘intBitSetIsDisjoint’:
  intbitset/intbitset_impl.c:414:40: warning: passing argument 1 of ‘intBitSetAdaptMin’ discards ‘const’ qualifier from pointer target type [-Wdiscarded-qualifiers]
    414 |   xend = x->bitset + intBitSetAdaptMin(x, y);
        |                                        ^
  intbitset/intbitset_impl.c:247:40: note: expected ‘IntBitSet * const’ but argument is of type ‘const IntBitSet *’
    247 | int intBitSetAdaptMin(IntBitSet *const x, IntBitSet *const y) {
        |                       ~~~~~~~~~~~~~~~~~^
  intbitset/intbitset_impl.c:414:43: warning: passing argument 2 of ‘intBitSetAdaptMin’ discards ‘const’ qualifier from pointer target type [-Wdiscarded-qualifiers]
    414 |   xend = x->bitset + intBitSetAdaptMin(x, y);
        |                                           ^
  intbitset/intbitset_impl.c:247:60: note: expected ‘IntBitSet * const’ but argument is of type ‘const IntBitSet *’
    247 | int intBitSetAdaptMin(IntBitSet *const x, IntBitSet *const y) {
        |                                           ~~~~~~~~~~~~~~~~~^

[pombredanne]

This is still the case as of the latest Cython.
The C code is generated, so the issue is either:

1. not fixable
2. fixable in intbitset.pyx

Would you care digging in this for a solution?

[stefan6419846]

intbitset_impl.c is not auto-generated, thus these tend to be errors which are fixable by us. Unfortunately, my general C knowledge is rather limited.

For PyObject_AsReadBuffer: They are defined inside the intbitset.pyx file and thus modifiable by us as well:

intbitset/intbitset/intbitset.pyx

Line 194 in 440ccf9

if PyObject_AsReadBuffer(tmp, &buf, &size) < 0:

intbitset/intbitset/intbitset.pyx

Line 584 in 440ccf9

if PyObject_AsReadBuffer(tmp, &buf, &size) < 0:

These have been discussed in #93 already.