9. Makefile.in / configure

If an application should build on many different systems, it needs to be properly configured to adapt to the particular features of any supported system. To solve this problem, there is a tool named autoconf which a software author can use for this purpose. With autoconf the author/ developer creates a file named configure that is then included in the source package and should be executed by the installer (configure is simply a shell script). When you execute configure, it will

• probe your system for (hopefully) all relevant features,

• generate a Makefile from an input file called Makefile.in, and

• generate a file config.h from an input file called config.h.in.

Note that more output files may get created. A typical run looks like:

    bash$ ./configure    
    creating cache ./config.cache
    checking for a BSD compatible install... /usr/bin/ginstall -c
    …
    checking for gcc... gcc
    …
    checking for gtk-config... /usr/bin/gtk-config
    checking for GTK - version >= 1.2.0... yes
    …
    checking for getpagesize... yes
    checking for working mmap... yes
    …
    creating Makefile
    creating src/Makefile
    creating config.h
    

You can see that configure checks for the presence of the compiler (gcc) as well as for an install utility. It also looks for gtk+, which is a widget library (i.e. it creates windows, buttons, text entry fields and so on for graphical user interfaces), checks for system-specific items (getpagesize, mmap), and finally creates Makefile, Makefile.in, and config.h. Note that only a small part of the output is shown in the example above.

configure should be invoked as ./configure and can take arguments. Some of the more interesting ones are: