Re: project in multiply directories

[Bob Friesenhahn]

On Mon, 28 Sep 2009, Alfred M. Szmidt wrote:

>   There is an article called "recursive make considered harmful".
>   According to it, you should have just one Makefile.am in top level
>   with all the rules (all libs etc). By this, make can show its
>   strengths best. Often, a Makefile.am "per directory" seems to be
>   used, but for a new project today this should be avoided.  It just
>   slows things down and leads to unneeded compiler calls.
>
> I'm sorry, but where on earth did you get this terrible information?
>
> A Makefile.am per directory is precisly what should be used, it
> doesn't incure any extra compiler calls.  It also makes it easy to
> build seperate parts of the tree.

The main advantage of a Makefile per directory is that it makes it 
easier to request building seperate parts of the tree.  Otherwise the 
approach can waste quite a lot of build performance since each 
sub-make must stat(2) all off the files required by the Makefile 
target as well as all of the generated source file dependencies, and 
there is quite a lot of redundant processing (e.g re-linking) which 
does not need to occur.  A non-recursive build can help avoid 
depending on archive libraries and "convenience" libraries which often 
consume quite a bit of the build time.

I have taken a number of large Automake-based projects (C and C++) to 
non-recursive builds and have not regretted it.

Bob
--
Bob Friesenhahn
address@hidden, http://www.simplesystems.org/users/bfriesen/
GraphicsMagick Maintainer,    http://www.GraphicsMagick.org/