File: autoconf.info,  Node: Erlang Libraries,  Prev: C and Posix Variants,  Up: Existing Tests

5.13 Erlang Libraries
=====================

The following macros check for an installation of Erlang/OTP, and for
the presence of certain Erlang libraries.  All those macros require the
configuration of an Erlang interpreter and an Erlang compiler (*note
Erlang Compiler and Interpreter::).

 -- Macro: AC_ERLANG_SUBST_ERTS_VER
     Set the output variable ‘ERLANG_ERTS_VER’ to the version of the
     Erlang runtime system (as returned by Erlang's
     ‘erlang:system_info(version)’ function).  The result of this test
     is cached if caching is enabled when running ‘configure’.  The
     ‘ERLANG_ERTS_VER’ variable is not intended to be used for testing
     for features of specific ERTS versions, but to be used for
     substituting the ERTS version in Erlang/OTP release resource files
     (‘.rel’ files), as shown below.

 -- Macro: AC_ERLANG_SUBST_ROOT_DIR
     Set the output variable ‘ERLANG_ROOT_DIR’ to the path to the base
     directory in which Erlang/OTP is installed (as returned by Erlang's
     ‘code:root_dir/0’ function).  The result of this test is cached if
     caching is enabled when running ‘configure’.

 -- Macro: AC_ERLANG_SUBST_LIB_DIR
     Set the output variable ‘ERLANG_LIB_DIR’ to the path of the library
     directory of Erlang/OTP (as returned by Erlang's ‘code:lib_dir/0’
     function), which subdirectories each contain an installed
     Erlang/OTP library.  The result of this test is cached if caching
     is enabled when running ‘configure’.

 -- Macro: AC_ERLANG_CHECK_LIB (LIBRARY, [ACTION-IF-FOUND],
          [ACTION-IF-NOT-FOUND])
     Test whether the Erlang/OTP library LIBRARY is installed by calling
     Erlang's ‘code:lib_dir/1’ function.  The result of this test is
     cached if caching is enabled when running ‘configure’.
     ACTION-IF-FOUND is a list of shell commands to run if the library
     is installed; ACTION-IF-NOT-FOUND is a list of shell commands to
     run if it is not.  Additionally, if the library is installed, the
     output variable ‘ERLANG_LIB_DIR_LIBRARY’ is set to the path to the
     library installation directory, and the output variable
     ‘ERLANG_LIB_VER_LIBRARY’ is set to the version number that is part
     of the subdirectory name, if it is in the standard form
     (‘LIBRARY-VERSION’).  If the directory name does not have a version
     part, ‘ERLANG_LIB_VER_LIBRARY’ is set to the empty string.  If the
     library is not installed, ‘ERLANG_LIB_DIR_LIBRARY’ and
     ‘ERLANG_LIB_VER_LIBRARY’ are set to ‘"not found"’.  For example, to
     check if library ‘stdlib’ is installed:

          AC_ERLANG_CHECK_LIB([stdlib],
            [echo "stdlib version \"$ERLANG_LIB_VER_stdlib\""
             echo "is installed in \"$ERLANG_LIB_DIR_stdlib\""],
            [AC_MSG_ERROR([stdlib was not found!])])

     The ‘ERLANG_LIB_VER_LIBRARY’ variables (set by
     ‘AC_ERLANG_CHECK_LIB’) and the ‘ERLANG_ERTS_VER’ variable (set by
     ‘AC_ERLANG_SUBST_ERTS_VER’) are not intended to be used for testing
     for features of specific versions of libraries or of the Erlang
     runtime system.  Those variables are intended to be substituted in
     Erlang release resource files (‘.rel’ files).  For instance, to
     generate a ‘example.rel’ file for an application depending on the
     ‘stdlib’ library, ‘configure.ac’ could contain:

          AC_ERLANG_SUBST_ERTS_VER
          AC_ERLANG_CHECK_LIB([stdlib],
            [],
            [AC_MSG_ERROR([stdlib was not found!])])
          AC_CONFIG_FILES([example.rel])

     The ‘example.rel.in’ file used to generate ‘example.rel’ should
     contain:

          {release,
              {"@PACKAGE@", "@VERSION@"},
              {erts, "@ERLANG_ERTS_VER@"},
              [{stdlib, "@ERLANG_LIB_VER_stdlib@"},
               {@PACKAGE@, "@VERSION@"}]}.

   In addition to the above macros, which test installed Erlang
libraries, the following macros determine the paths to the directories
into which newly built Erlang libraries are to be installed:

 -- Macro: AC_ERLANG_SUBST_INSTALL_LIB_DIR

     Set the ‘ERLANG_INSTALL_LIB_DIR’ output variable to the directory
     into which every built Erlang library should be installed in a
     separate subdirectory.  If this variable is not set in the
     environment when ‘configure’ runs, its default value is
     ‘${libdir}/erlang/lib’.

 -- Macro: AC_ERLANG_SUBST_INSTALL_LIB_SUBDIR (LIBRARY, VERSION)

     Set the ‘ERLANG_INSTALL_LIB_DIR_LIBRARY’ output variable to the
     directory into which the built Erlang library LIBRARY version
     VERSION should be installed.  If this variable is not set in the
     environment when ‘configure’ runs, its default value is
     ‘$ERLANG_INSTALL_LIB_DIR/LIBRARY-VERSION’, the value of the
     ‘ERLANG_INSTALL_LIB_DIR’ variable being set by the
     ‘AC_ERLANG_SUBST_INSTALL_LIB_DIR’ macro.