Unexpected heap growth in gctest on Linux with malloc redirection

[ivmai]

Source: master (98b5d38)
Build: https://github.com/ivmai/bdwgc/actions/runs/7187064946/job/19573829443
Host: Linux/x64
Config: ubuntu-latest gcc thr:on rwlock::on redir:on dll:off cpp::on
Occurrence: rare
Output (gctest):

Completed 6 tests
Allocated 11792254 collectable objects
Allocated 1224 uncollectable objects
Allocated 720438 atomic objects
Reallocated 36 objects
Garbage collection after fork is tested too
Finalized 13221/13221 objects - finalization is probably OK
Total number of bytes allocated is 1156269712
Total memory use by allocated blocks is 35934208 bytes
Final heap size is 5279744 bytes
Unexpected heap growth - collector may be broken (heapsize: 161329152, expected: 159383552)
Test failed

[ivmai]

Related: #538

[ivmai]

Source: master (2414089)
Build: https://github.com/ivmai/bdwgc/actions/runs/7912256661/job/21597721839
Config: ubuntu-latest clang thr:on rwlock:on redir:on dll:on cpp:on