7.3 An Alternative Approach to Subdirectories

If you've ever read Peter Miller's excellent paper, Recursive Make Considered Harmful, the preceding sections on the use of subdirectories will probably come as unwelcome advice. For those who haven't read the paper, Miller's main thesis is that recursive make invocations are both slow and error-prone.

Automake provides sufficient cross-directory support (3) to enable you to write a single ‘Makefile.am’ for a complex multi-directory package.

By default an installable file specified in a subdirectory will have its directory name stripped before installation. For instance, in this example, the header file will be installed as ‘$(includedir)/stdio.h’:

include_HEADERS = inc/stdio.h

However, the ‘nobase_’ prefix can be used to circumvent this path stripping. In this example, the header file will be installed as ‘$(includedir)/sys/types.h’:

nobase_include_HEADERS = sys/types.h

‘nobase_’ should be specified first when used in conjunction with either ‘dist_’ or ‘nodist_’ (see section Fine-grained Distribution Control). For instance:

nobase_dist_pkgdata_DATA = images/vortex.pgm sounds/whirl.ogg

Finally, note that a variable using the ‘nobase_’ prefix can often be replaced by several variables, one for each destination directory (see section The Uniform Naming Scheme). For instance, the last example could be rewritten as follows:

imagesdir = $(pkgdatadir)/images
soundsdir = $(pkgdatadir)/sounds
dist_images_DATA = images/vortex.pgm
dist_sounds_DATA = sounds/whirl.ogg

This latter syntax makes it possible to change one destination directory without changing the layout of the source tree.

Currently, ‘nobase_*_LTLIBRARIES’ are the only exception to this rule, in that there is no particular installation order guarantee for an otherwise equivalent set of variables without ‘nobase_’ prefix.