Make compiles all the files every time including the unchanged files

Question

I don\'t know why the Make recompiles all the files every time including the unchanged files, it takes a long time. I searched the Stack Overflow and found some solutions, b

Answer 1

You've not specified any dependencies for each object. Make doesn't have any way of knowing whether the headers that source files depend on have changed or any other dependencies of a source file. For example if some 'definition' file changes, you might need to regenerate headers, which in turn requires re-compilation of dependent source files.

In order to have Make conditionally compile based on dependents you must tell Make what the dependencies are. Be warned though, if you get this wrong you can end up in a nasty situation where you make changes that are not picked up because your dependency list is incorrect, or only partially picked up by some files.

I'd suggest looking at these topics on auto generation of dependencies. Manually managing them is OK for very tiny projects but scales poorly with many files. In addition, maintaining complex Makefiles is a task very few enjoy.

Makefile (Auto-Dependency Generation)

Makefile, header dependencies

For MAKE reference see: http://kirste.userpage.fu-berlin.de/chemnet/use/info/make/make_4.html