RE: updating target at the end of recipe, after updating prerequisites, might not work?

[Mark Galeck (CW)]

OK.  So sometimes the modify timestamps are rounded to the nearest second and 
sometimes don't.  

Then this causes problems for makefiles...  Because if you are updating 
prerequisites of a target with a non-rounding utility, and then updating the 
target with a rounding utility, and all of that updating takes only a small 
fraction of a second, then very often the timestamp of the target will end up 
rounded down, and will be "older" than the timestamps of it's prerequisites.  

That means, on the next rebuild, which should otherwise not update anything, 
you may end up rebuilding the target again.  

How do make gurus deal with this problem Paul?

I see that "make" uses the "modify" timestamps for comparisons between target 
and prerequisites.  

For me, echo foo > xyz does not _always_ set modify timestamp for xyz to 
sub-second resolution.  In some directories, it does, but where I care, it does 
not.  Must be mounted filesystem-dependency.  

I was thinking  to do 

echo "" >> foobar

when needed, but with this not working, how would you do it?  

Thank you,

Mark