Most packages export one or more header files defining their public interface. For example the C library exports header files such as stdio.h and ctype.h . If the package follows the directory layout conventions then the exported header files will normally be found in the package's include sub-directory. For packages which do not follow these conventions, typically simple ones for which a complicated sub-directory hierarchy is undesirable, there has to be an alternative way of specifying which header file or files define the public interface. The include_files property provides support for this.
By default, if a package does not have an include subdirectory and it does not have an include_files property then all files with a suffix of .h , .hxx , .inl or .inc will be treated as public header files. However some of these may be private files containing implementation details. If there is an include_files property then only the files listed in that property will be exported.