C compilation warnings, signedness comparison, uninitialized #758

$ pip install -vv -e .

  numcodecs/blosc.c: In function ‘__pyx_pf_9numcodecs_5blosc_22decompress’:
  numcodecs/blosc.c:6049:38: warning: comparison of integer expressions of different signedness: ‘Py_ssize_t’ {aka ‘long int’} and ‘size_t’ {aka ‘long unsigned int’} [-Wsign-compare]
   6049 |     __pyx_t_2 = (__pyx_v_dest_nbytes < __pyx_v_nbytes);
        |                                      ^
  In function ‘__Pyx_PyLong_From_int’,
      inlined from ‘__pyx_pf_9numcodecs_5blosc_20compress’ at numcodecs/blosc.c:5659:17,
      inlined from ‘__pyx_pw_9numcodecs_5blosc_21compress’ at numcodecs/blosc.c:4751:13:
  numcodecs/blosc.c:14883:20: warning: ‘__pyx_v_cbytes’ may be used uninitialized [-Wmaybe-uninitialized]
  14883 |             return PyLong_FromLong((long) value);
        |                    ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~
  numcodecs/blosc.c: In function ‘__pyx_pw_9numcodecs_5blosc_21compress’:
  numcodecs/blosc.c:4775:7: note: ‘__pyx_v_cbytes’ was declared here
   4775 |   int __pyx_v_cbytes;
        |       ^~~~~~~~~~~~~~

...
  numcodecs/zstd.c: In function ‘__pyx_pf_9numcodecs_4zstd_2decompress’:
  numcodecs/zstd.c:3816:38: warning: comparison of integer expressions of different signedness: ‘Py_ssize_t’ {aka ‘long int’} and ‘size_t’ {aka ‘long unsigned int’} [-Wsign-compare]
   3816 |     __pyx_t_3 = (__pyx_v_dest_nbytes < __pyx_v_dest_size);
        |                                      ^
...
  numcodecs/lz4.c: In function ‘__pyx_pf_9numcodecs_3lz4_2decompress’:
  numcodecs/lz4.c:3449:38: warning: comparison of integer expressions of different signedness: ‘int’ and ‘long unsigned int’ [-Wsign-compare]
   3449 |     __pyx_t_3 = (__pyx_v_source_size < (sizeof(uint32_t)));
        |                                      ^