Re: [PATCH] up_to_date_p: treat equal mtime as outdated.

[Paul Eggert]

On 4/13/20 4:21 PM, Harald van Dijk wrote:
> For better or worse, FAT is the most universally accepted file system, and for 
> that reason it is widely used. It does not even support second precision 
> timestamps.

Let's not worry much about that. In practice, little development of 
Automake-using software occurs on FAT file systems, and even if it did those 
file systems are low priority for GNU development.

I just checked, and GNU Make uses high-resolution file timestamps when 
available, and considers a file to be up-to-date if it has exactly the same 
timestamp as its dependency. I suspect that this is because Makefile rules like 
this:

a: b
        cp -p b a

would otherwise cause needless work if one ran 'make; make'.

If Automake followed the same rule as GNU Make, we'd at least have the benefit 
of consistency....