libtool: Autoconf macros

1 
1 5.1 Autoconf macros exported by libtool
1 =======================================
1 
1 Libtool uses a number of macros to interrogate the host system when it
1 is being built, and you can use some of them yourself too.  Although
1 there are a great many other macros in the libtool installed m4 files,
1 these do not form part of the published interface, and are subject to
1 change between releases.
1 
1 Macros in the 'LT_CMD_' namespace check for various shell commands:
1 
1  -- Macro: LT_CMD_MAX_LEN
1      Finds the longest command line that can be safely passed to
1      '$SHELL' without being truncated, and store in the shell variable
1      '$max_cmd_len'.  It is only an approximate value, but command lines
1      of this length or shorter are guaranteed not to be truncated.
1 
1 Macros in the 'LT_FUNC_' namespace check characteristics of library
1 functions:
1 
1  -- Macro: LT_FUNC_DLSYM_USCORE
1      'AC_DEFINE' the preprocessor symbol 'DLSYM_USCORE' if we have to
1      add an underscore to symbol-names passed in to 'dlsym'.
1 
1 Macros in the 'LT_LIB_' namespace check characteristics of system
1 libraries:
1 
1  -- Macro: LT_LIB_M
1      Set 'LIBM' to the math library or libraries required on this
1      machine, if any.
1 
1  -- Macro: LT_LIB_DLLOAD
1      This is the macro used by 'libltdl' to determine what dlloaders to
1      use on this machine, if any.  Several shell variables are set (and
1      'AC_SUBST'ed) depending on the dlload interfaces are available on
1      this machine.  'LT_DLLOADERS' contains a list of libtool libraries
1      that can be used, and if necessary also sets 'LIBADD_DLOPEN' if
1      additional system libraries are required by the 'dlopen' loader,
1      and 'LIBADD_SHL_LOAD' if additional system libraries are required
1      by the 'shl_load' loader, respectively.  Finally some symbols are
1      set in 'config.h' depending on the loaders that are found to work:
1      'HAVE_LIBDL', 'HAVE_SHL_LOAD', 'HAVE_DYLD', 'HAVE_DLD'.
1 
1 Macros in the 'LT_PATH_' namespace search the system for the full path
1 to particular system commands:
1 
1  -- Macro: LT_PATH_LD
1      Add a '--with-gnu-ld' option to 'configure'.  Try to find the path
1      to the linker used by '$CC', and whether it is the GNU linker.  The
1      result is stored in the shell variable '$LD', which is
1      'AC_SUBST'ed.
1 
1  -- Macro: LT_PATH_NM
1      Try to find a BSD-compatible 'nm' or a MS-compatible 'dumpbin'
1      command on this machine.  The result is stored in the shell
1      variable '$NM', which is 'AC_SUBST'ed.
1 
1 Macros in the 'LT_SYS_' namespace probe for system characteristics:
1 
1  -- Macro: LT_SYS_DLOPEN_SELF
1      Tests whether a program can dlopen itself, and then also whether
1      the same program can still dlopen itself when statically linked.
1      Results are stored in the shell variables '$enable_dlopen_self' and
1      'enable_dlopen_self_static' respectively.
1 
1  -- Macro: LT_SYS_DLOPEN_DEPLIBS
1      Define the preprocessor symbol 'LTDL_DLOPEN_DEPLIBS' if the OS
1      needs help to load dependent libraries for 'dlopen' (or
1      equivalent).
1 
1  -- Macro: LT_SYS_DLSEARCH_PATH
1      Define the preprocessor symbol 'LT_DLSEARCH_PATH' to the system
1      default library search path.
1 
1  -- Macro: LT_SYS_MODULE_EXT
1      Define the preprocessor symbol 'LT_MODULE_EXT' to the extension
1      used for runtime loadable modules.  If you use libltdl to open
1      modules, then you can simply use the libtool library extension,
1      '.la'.
1 
1  -- Macro: LT_SYS_MODULE_PATH
1      Define the preprocessor symbol 'LT_MODULE_PATH_VAR' to the name of
1      the shell environment variable that determines the run-time module
1      search path.
1 
1  -- Macro: LT_SYS_SYMBOL_USCORE
1      Set the shell variable 'sys_symbol_underscore' to 'no' unless the
1      compiler prefixes global symbols with an underscore.
1