Re: POSIX ruling on up-to-date vs. identical timestamps

[Paul Eggert]

Paul Smith wrote:

> It needs to be considered carefully.

How about having GNU 'make' do what GNU 'cp -u' does?

The idea is to infer filesystem timestamp resolution by looking at every 
file timestamp that crosses your desk.  When you see a file timestamp 
whose tv_nsec is nonzero modulo 1000000, for example, you know that its 
filesystem's resolution is finer-grained than 1 millisecond.  When 
computation starts, you are conservative and assume that filesystems 
have 1-second resolution, but as computation goes on you gain more 
information about each filesystem and can become less and less conservative.

It's a hack, but the heuristic doesn't require any system calls (and for 
what it's worth we don't get bug reports about it...).

This idea is implemented by Gnulib's 'utimecmp' module, which GNU Make 
is of course welcome to steal.