Info Catalog automake-1.16: Conditional Libtool Sources automake-1.16: A Shared Library automake-1.16: Libtool Modules

automake-1.16: Libtool Convenience Libraries

 
 8.3.5 Libtool Convenience Libraries
 -----------------------------------
 
 Sometimes you want to build libtool libraries that 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 directory-less
 variables such as ‘noinst_LTLIBRARIES’, ‘check_LTLIBRARIES’, or even
 ‘EXTRA_LTLIBRARIES’.  Unlike installed libtool libraries they do not
 need an ‘-rpath’ flag at link time (this is in fact 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 \
        ...
 
    When using such a setup, beware that ‘automake’ will assume
 ‘libtop.la’ is to be linked with the C linker.  This is because
 ‘libtop_la_SOURCES’ is empty, so ‘automake’ picks C as default language.
 If ‘libtop_la_SOURCES’ was not empty, ‘automake’ would select the linker
 as explained in ⇒How the Linker is Chosen.
 
    If one of the sublibraries contains non-C source, it is important
 that the appropriate linker be chosen.  One way to achieve this is to
 pretend that there is such a non-C file among the sources of the
 library, thus forcing ‘automake’ to select the appropriate linker.  Here
 is the top-level ‘Makefile’ of our example updated to force C++ linking.
 
      SUBDIRS = sub1 sub2 ...
      lib_LTLIBRARIES = libtop.la
      libtop_la_SOURCES =
      # Dummy C++ source to cause C++ linking.
      nodist_EXTRA_libtop_la_SOURCES = dummy.cxx
      libtop_la_LIBADD = \
        sub1/libsub1.la \
        sub2/libsub2.la \
        ...
 
    ‘EXTRA_*_SOURCES’ variables are used to keep track of source files
 that might be compiled (this is mostly useful when doing conditional
 compilation using ‘AC_SUBST’; ⇒Conditional Libtool Sources), and
 the ‘nodist_’ prefix means the listed sources are not to be distributed
 (⇒Program and Library Variables).  In effect the file ‘dummy.cxx’
 does not need to exist in the source tree.  Of course if you have some
 real source file to list in ‘libtop_la_SOURCES’ there is no point in
 cheating with ‘nodist_EXTRA_libtop_la_SOURCES’.
 

Info Catalog automake-1.16: Conditional Libtool Sources automake-1.16: A Shared Library automake-1.16: Libtool Modules