> We can finesse this by saying in the SRFI something like
> "Implementations are encouraged but not required to use POSIX
> [whatever]at if the supplied /path/ is greater than PATH_MAX.

Note that POSIX allows PATH_MAX to be dynamic. One should fetch the
current value via sysconf():
<https://pubs.opengroup.org/onlinepubs/9699919799/functions/sysconf.html>.

More fun from that page:

"Some values, such as {PATH_MAX}, are sometimes so large that they must
not be used to, say, allocate arrays. The sysconf() function returns a
negative value to show that this symbolic constant is not even defined
in this case."