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

automake-1.16: Conditional Libtool Libraries

 
 8.3.3 Building Libtool Libraries Conditionally
 ----------------------------------------------
 
 Like conditional programs (⇒Conditional Programs), there are two
 main ways to build conditional libraries: using Automake conditionals or
 using Autoconf ‘AC_SUBST’itutions.
 
    The important implementation detail you have to be aware of is that
 the place where a library will be installed matters to libtool: it needs
 to be indicated _at link-time_ using the ‘-rpath’ option.
 
    For libraries whose destination directory is known when Automake
 runs, Automake will automatically supply the appropriate ‘-rpath’ option
 to libtool.  This is the case for libraries listed explicitly in some
 installable ‘_LTLIBRARIES’ variables such as ‘lib_LTLIBRARIES’.
 
    However, for libraries determined at configure time (and thus
 mentioned in ‘EXTRA_LTLIBRARIES’), Automake does not know the final
 installation directory.  For such libraries you must add the ‘-rpath’
 option to the appropriate ‘_LDFLAGS’ variable by hand.
 
    The examples below illustrate the differences between these two
 methods.
 
    Here is an example where ‘WANTEDLIBS’ is an ‘AC_SUBST’ed variable set
 at ‘./configure’-time to either ‘libfoo.la’, ‘libbar.la’, both, or none.
 Although ‘$(WANTEDLIBS)’ appears in the ‘lib_LTLIBRARIES’, Automake
 cannot guess it relates to ‘libfoo.la’ or ‘libbar.la’ at the time it
 creates the link rule for these two libraries.  Therefore the ‘-rpath’
 argument must be explicitly supplied.
 
      EXTRA_LTLIBRARIES = libfoo.la libbar.la
      lib_LTLIBRARIES = $(WANTEDLIBS)
      libfoo_la_SOURCES = foo.c ...
      libfoo_la_LDFLAGS = -rpath '$(libdir)'
      libbar_la_SOURCES = bar.c ...
      libbar_la_LDFLAGS = -rpath '$(libdir)'
 
    Here is how the same ‘Makefile.am’ would look using Automake
 conditionals named ‘WANT_LIBFOO’ and ‘WANT_LIBBAR’.  Now Automake is
 able to compute the ‘-rpath’ setting itself, because it’s clear that
 both libraries will end up in ‘$(libdir)’ if they are installed.
 
      lib_LTLIBRARIES =
      if WANT_LIBFOO
      lib_LTLIBRARIES += libfoo.la
      endif
      if WANT_LIBBAR
      lib_LTLIBRARIES += libbar.la
      endif
      libfoo_la_SOURCES = foo.c ...
      libbar_la_SOURCES = bar.c ...
 

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