"generating prerequisites automatically" causes all *.d makefiles to be regenerated?

[Mark Galeck (CW)]

Hello, 

I read and implemented the guidelines in the section of the GNU Make manual “4.14 Generating Prerequisities Automatically”.  It works great, for each C source file, I have a corresponding .d file, which is also a makefile, generated, and all those makefiles are included in the main makefile with the “include” directive.  In the .d file are header file dependencies for that particular C file. 

 

There seems to be a problem however with this approach.  I write “seems” because it must be that I don’t understand something, as I am sure the GNU Make manual recommends the “right thing”.  Please help me understand what I am missing.

 

 

 

The problem I have is:  when I do

>make foobar.o

 

make then tries to generate all these *.d files, all of them – not just the one that is needed foobar.d !  That is not good –takes a lot of time if I just want one foobar.o.  Also, what is worse,

if I do

 

>make clean

 

Then again, all the *.d files are generated first, takes a very long time, before everything is deleted. 

 

 

How to do it so that only the *.d files that are really needed are generated, and none are generated on make clean?

 

Thank you for any insight,

 

Mark