Makefile with .mod files

[FX Coudert]

> I'm having some problems with a Makefile for a Fortran program, and
> I've tracked it down to the fact that .mod files don't have their
> timestamp updated when compiling if they don't change.

This is a change from 4.2, IIRC, and it was done because users  
complained that .mod files had their timestamps updated while not  
changing, which triggered massive useless recompilations because of  
Makefile dependencies ;-)

> all: a.o b.o
>
> a.mod a.o: a.f90 b.mod
>         gfortran -c $<
>
> b.mod b.o: b.f90
>         gfortran -c $<

> Now I have to run "make" twice, I guess it's because make does not  
> know
> b.mod can change due to a change in b.f90, as it is an order-only
> dependency...
>
> So, is there a solution for this?

Yes, I believe there is; the following Makefile seems to work fine:

all: a.o b.o

a.o: a.f90 b.mod
         gfortran -c $<

b.o: b.f90
         gfortran -c $<

b.mod: b.f90 b.o
         @true

a.mod: a.f90 a.o
         @true


I know it's not as easy as one could hope, but I intend to add  
options to generate Makefile dependencies (-M options) in gfortran-4.4.

Regards,
FX