Re: Re-evaluate date of file after updating?

[Norbert Nemec]

Indeed! Thanks! I thought I had tried this, but obviously not in the 
right combination.

Isn't it funny? I was trying more and more complex solutions for the 
problem and was actually close to giving up. Now it turns out that my 
very first attempt was actually correct, except for the characters "; 
@:" ...

!"&^%^&!"%!&^%!!!!!

Greetings,
Norbert


Paul Smith wrote:
> On Mon, 2010-03-29 at 17:50 +0100, Norbert Nemec wrote:
>
>   
> > is there a way to define dependencies that re-evaluate the date of a 
> > file *after* updating it? Currently, the MAKE program blindly assumes 
> > that the target is actually modified its commands.
> >     
>
> No it doesn't.  If the command script doesn't modify the timestamp on
> the generated file then targets that depend on it won't consider it to
> be updated.  This is very commonly used.
>
>   
> > My best attempt at implementing this kind of dependencies in a Makefile 
> > is as follows
> >     
>
>   
> > lib.mod: lib.o
> > lib.o: lib.f90
> >         mv lib.mod lib.mod.old
> >         f90 -c lib.f90
> >         diff -qN lib.mod.old lib.mod > /dev/null && mv lib.mod.old lib.mod
> >         rm -f lib.mod.old
> >     
>
>   
> > This behaves nearly as needed, but unfortunately, the rule for prog.o 
> > does not care whether lib.mod has actually changed. It always recreates 
> > prog.o when lib.f90 was modified.
> >     
>
> That's because there's no command sequence for lib.mod.  If you add a
> "do nothing" command to the lib.mod: lib.o rule, I think it will work as
> you expect (note I didn't test this):
>
>         lib.mod: lib.o ; @:
>
>
>   


--
_________________________________________Norbert Nemec
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