Libtool Convenience Libraries

Sometimes you want to build libtool libraries which should not be installed. These are called libtool convenience libraries and are typically used to encapsulate many sublibraries, later gathered into one big installed library.

Libtool convenience libraries are declared by noinst_LTLIBRARIES, check_LTLIBRARIES, or even EXTRA_LTLIBRARIES. Unlike installed libtool libraries they do not need an -rpath flag at link time (actually this is the only difference).

Convenience libraries listed in noinst_LTLIBRARIES are always built. Those listed in check_LTLIBRARIES are built only upon make check. Finally, libraries listed in EXTRA_LTLIBRARIES are never built explicitly: Automake outputs rules to build them, but if the library does not appear as a Makefile dependency anywhere it won't be built (this is why EXTRA_LTLIBRARIES is used for conditional compilation).

Here is a sample setup merging libtool convenience libraries from subdirectories into one main libtop.la library.

     # -- Top-level Makefile.am --
     SUBDIRS = sub1 sub2 ...
     lib_LTLIBRARIES = libtop.la
     libtop_la_SOURCES =
     libtop_la_LIBADD = \
       sub1/libsub1.la \
       sub2/libsub2.la \
       ...
     
     # -- sub1/Makefile.am --
     noinst_LTLIBRARIES = libsub1.la
     libsub1_la_SOURCES = ...
     
     # -- sub2/Makefile.am --
     # showing nested convenience libraries
     SUBDIRS = sub2.1 sub2.2 ...
     noinst_LTLIBRARIES = libsub2.la
     libsub2_la_SOURCES =
     libsub2_la_LIBADD = \
       sub21/libsub21.la \
       sub22/libsub22.la \
       ...