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(libtool.info)Dlpreopening

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Dlpreopening
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   Libtool provides special support for dlopening libtool object and
libtool library files, so that their symbols can be resolved _even on
platforms without any `dlopen' and `dlsym' functions_.

   Consider the following alternative ways of loading code into your
program, in order of increasing "laziness":

  1. Linking against object files that become part of the program
     executable, whether or not they are referenced.  If an object file
     cannot be found, then the linker refuses to create the executable.

  2. Declaring a static library to the linker, so that it is searched
     at link time in order to satisfy any undefined references in the
     above object files.  If the static library cannot be found, then
     the linker refuses to link the executable.

  3. Declaring a shared library to the runtime linker, so that it is
     searched at runtime in order to satisfy any undefined references
     in the above files.  If the shared library cannot be found, then
     the dynamic linker aborts the program before it runs.

  4. Dlopening a module, so that the application can resolve its own,
     dynamically-computed references.  If there is an error opening the
     module, or the module is not found, then the application can
     recover without crashing.

   Libtool emulates `-dlopen' on static platforms by linking objects
into the program at compile time, and creating data structures that
represent the program's symbol table.

   In order to use this feature, you must declare the objects you want
your application to dlopen by using the `-dlopen' or `-dlpreopen' flags
when you link your program (Note: Link mode).

 - Structure: struct lt_dlsymlist { const char *NAME; lt_ptr ADDRESS; }
     The NAME attribute is a null-terminated character string of the
     symbol name, such as `"fprintf"'.  The ADDRESS attribute is a
     generic pointer to the appropriate object, such as `&fprintf'.

 - Variable: const lt_dlsymlist * lt_preloaded_symbols
     An array of LT_SYMBOL structures, representing all the preloaded
     symbols linked into the program. For each `-dlpreloaded' file
     there is an element with the NAME of the file and a ADDRESS of
     `0', followed by all symbols exported from this file.  For the
     executable itself the special name @PROGRAM@ is used.  The last
     element has a NAME and ADDRESS of `0'.

   Some compilers may allow identifiers which are not valid in ANSI C,
such as dollar signs.  Libtool only recognizes valid ANSI C symbols (an
initial ASCII letter or underscore, followed by zero or more ASCII
letters, digits, and underscores), so non-ANSI symbols will not appear
in LT_PRELOADED_SYMBOLS.