[b84330808]

Fixes #1198, fixes #1199, and two more size problems in the same functions:

• msgpack_zbuffer_init(zbuf, level, 0) stored 0, so the first write made a zero-size buffer and failed, and the next realloc(ptr, 0) freed it while zbuf->data kept the pointer, which destroy then freed again. 0 now means the default, as in msgpack_vrefbuffer_init().
• msgpack_zbuffer_expand() doubled the size with no overflow check. It now returns false.
• msgpack_zbuffer_write() cast len to the 32-bit avail_in, so a write of 4 GiB + 1 bytes compressed 1 byte and returned 0. Long writes now go to zlib in several steps.
• expand cast the free space to the 32-bit avail_out. At exactly 4 GiB free that is 0, so write fails and flush spins forever once the output reaches 4 GiB. It now saturates.

zbuffer_sizes_c gets its own translation unit with a stand-in deflate() that only counts input, so the tests don't need 4 GiB of data. The size tests fail without the header change (the expand one on both 32-bit and 64-bit) and pass with it.

[codecov-commenter]

⚠️ Please install the to ensure uploads and comments are reliably processed by Codecov.

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 62.33%. Comparing base (eabfe29) to head (fd5cf2c).
⚠️ Report is 13 commits behind head on c_master.
❗ Your organization needs to install the Codecov GitHub app to enable full functionality.

Additional details and impacted files

@@             Coverage Diff              @@
##           c_master    #1205      +/-   ##
============================================
+ Coverage     57.47%   62.33%   +4.86%     
============================================
  Files            10       10              
  Lines          1124     1147      +23     
  Branches        129      140      +11     
============================================
+ Hits            646      715      +69     
+ Misses          478      432      -46     

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.