Sometimes you may have changed a source file but you do not want to
recompile all the files that depend on it. For example, suppose you add a
macro or a declaration to a header file that many other files depend on.
Being conservative, make
assumes that any change in the header file
requires recompilation of all dependent files, but you know that they do not
need to be recompiled and you would rather not waste the time waiting for
them to compile.
If you anticipate the problem before changing the header file, you can
use the `-t' flag. This flag tells make
not to run the
commands in the rules, but rather to mark the target up to date by
changing its last-modification date. You would follow this procedure:
make
, the changes in the
header files will not cause any recompilation.
If you have already changed the header file at a time when some files do need recompilation, it is too late to do this. Instead, you can use the `-o file' flag, which marks a specified file as "old" (see section Summary of Options). This means that the file itself will not be remade, and nothing else will be remade on its account. Follow this procedure: