how to avoid unnecessary recompile when using configure script

[Andrew Wu]

I'm looking for help to make my build/make process smarter to 

avoid unnecessary recompilation. 

 

I'm using the following example to illustrate/describe my problem.

 

Say I have a source tree that has 3 directories: dir_1, dir_2, dir_3.

At the top of the source tree I have a Makefile.

 

Root/Makefile

        /dir_1/file_1.c

        /dir_2/file_2.c

        /dir_3/file_3.c

 

The top level Makefile consists of the following:

 

All:

cd dir_1; automake; autoheader; autoconf; ./configure; cd obj_dir_1; make

cd dir_2; automake; autoheader; autoconf; ./configure; cd obj_dir_2; make

cd dir_3; automake; autoheader; autoconf; ./configure; cd obj_dir_3; make

 

After I have my source tree in place first time, then I do a ¡®make¡¯ 

from Unix shell. Everything works as I expected. I got the first build 

from the scratch. 

 

After I make code changes only to dir_1/file_1.c,  I need to make 

a new build. Now if I simply run 'make' from under the root, 

everything will be recompiled, including the file_2.c, and file_3.c

which have not been modified at all.  The file_2.c is recompiled 

because the Makefile under dir_2/ is newly re-generated 

due to the ./configure is run. The same reason for the recompilation

of the dir_3/file_3.c.   

 

Obviously, file_2.c and file3_.c do not need

to be recompiled at all, for nothing has changed to 

them nor their build/make environment.

 

Could someone please send me some pointers regarding 

how to make the changes (in the Makefile or the 

configure script) to avoid the unnecessary re-compilation? 

I still want to simply run ¡®make¡¯ from the top level of the 

source tree though.

 

Thanks,

 

-andrew


                
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