The last few lines in figure 10 were used to declare
the dependencies.
For programs with less than five source files, this is manageable, but
for larger programs it is not.
Each time the #include structure of a program changes, the
dependencies change and the
Makefile has to be changed by hand, which is a nuisance for the
programmer and extremely error-prone.
Basically, there are a number of ways to automate the process of keeping
dependencies up to date. The one most easy to use (although not very
flexible) will be explained in this section.
There is a tool makedepend that automatically updates the dependencies
in our Makefile.
Figure 12: A modified Makefile that uses makedepend.
In Figure 12 we specify another target depend and
omit the hand written dependencies at the bottom lines.
If the user types make depend, the program makedepend
runs the preprocessor to find out which dependencies exists for each object
file.
It keeps a copy of our original Makefile in Makefile.bak
and appends the dependencies to our Makefile.
Each time we change our #include structure, we should run
``make depend'' prior to doing a plain ``make''.
An example of what is appended is shown in Figure 13.
Figure 13: A modified Makefile that uses makedepend.