Compiling and Linking with Your Own Libraries

When preparing your own library packages, it makes sense to treat each library as an entity that is separate from its header(s) and the programs that use it. Separating programs, libraries, and headers into distinct directories often makes it easier to prepare makefiles for each type of module. Also, it clarifies the structure of a software project.

It is not a good idea to have things pop up all over the file system as a result of running make.

A courteous and necessary convention of makefiles is that they only build files in the working directory, or in temporary subdirectories. Unless you are using make specifically to install files into a specific directory on an agreed-upon file system, it is regarded as very poor form for a makefile to produce output in another directory.

Building programs that rely on libraries in other directories adds several new wrinkles to the makefile. Up until now, everything needed has been in the directory, or else in one of the standard directories that are presumed to be stable. This is not true for user-supplied libraries that are part of a project under development.

Because these libraries aren't built automatically (there is no equivalent to hidden dependency checking for them), you must supply target entries for them. On the one hand, you need to ensure the libraries you link with are up to date.

On the other, you need to observe the convention that a makefile should only maintain files in the local directory. In addition, the makefile should not contain information duplicated in another.