Thanks, a few more things (hopefully we're getting to the end now).
"missing on many platforms" lists reallocarray as missing in FreeBSD 11.1,
NetBSD 8.0, and OpenBSD 5.6. But it's not missing in those versions: those are
the versions it was first introduced.
Please fit ChangeLog entries to 79 columns if possible.
When talking about a function FOO, say just "FOO", not "FOO()". Use the latter
form only when talking about calls to FOO with zero arguments.
The test could be easier to read and more useful if we got rid of the 'eight'
function and tried realloc_array with several different sizes. Also, there's no
need to free the array. E.g.,
for (n = 2; n != 0; n <<= 1)
if (reallocarray (NULL, (size_t) -1 / n + 1, n))