Unexpected heap growth in gctest single-threaded incremental mode with checksums on Linux/x64

[ivmai]

Source: release-8_0 (1a75627)
Build: https://app.travis-ci.com/github/ivmai/bdwgc/jobs/598128020
Host: Ubuntu 16.04.7 LTS / x64
Compiler: gcc (Ubuntu 5.4.0-6ubuntu1~16.04.12) 5.4.0 20160609
Occurrence: sometimes
How to build: ./configure --disable-threads --enable-checksums --disable-munmap --enable-cplusplus && make -j check

Output (gctest.log):

Switched to incremental mode
Emulating dirty bits with mprotect/signals
Completed 1 tests
Allocated 681888 collectable objects
Allocated 203 uncollectable objects
Allocated 1369470 atomic objects
Reallocated 126 objects
Finalized 2202/2202 objects - finalization is probably ok
Total number of bytes allocated is 105763975
Total memory use by allocated blocks is 5001216 bytes
Final heap size is 28024832 bytes
Unexpected heap growth - collector may be broken (heapsize: 28024832, expected: 25165824)
Test failed