Re: only run submake if that submake needs to be run?

[Noel Yap]

David Wuertele wrote:

> Boris> I think you are trying to solve the wrong problem. Here is some
> Boris> background.  There are two ways to write makefiles for a
> Boris> project: recursive (your case) and non-recursive.
>
> Your explanation hits the nail on the head.  You are correct about the
> speed issues and the parallel make issues inherent in my system.
>
> The reason I chose recursive in the first place was for a couple of
> reasons:
>
> 1.  I want to be able to run make in the sub-directory and have it
>     work
>
> 2.  I want to use the same variable namespace for all the makefiles.
>     For example, I don't want one of my users to have to create
>     variable names like:
>
>       my_program_OBJ := this.o that.o
>
>     I want them to be able to write:
>
>       OBJ := this.o that.o
>
>     This is an oversimplified example for the purposes of making the
>     point.  I want them to be able to copy their neighbor's Makefile
>     and not have to change all the variable names.
>
> Is there a way to write makefiles in a non-recursive fashion that will
> enable me to acheive both goals?

The first one, definitely.  You need to write the rules such that they don't 
care about the current directory.

The second one is a bit more complicated to say the least.  What I've done is 
to:

- define the function include-makefile that defines the __FILE__ variable.
- have makefiles "localize" their variable by prefixing them with $(__FILE__).  
For example, $(__FILE__).OBJ.

I've found that there are still problems with this and have thought that using 
functions to define rules might be a better way since UDF's are the only way in 
GNU make to have local variables.  I haven't implemented anything with this 
idea, yet, though.

HTH,
Noel