todo

GNU libtool 是一个通用库支持脚本

In the near future:
********************

* Port the migration of all code from ltconfig into libtool.m4 to the
multi-language-branch, so that CVS automake can remove its references
to ltconfig.

* Fix the following bugs in libltdl:
 - error reporting of tryall_dlopen():
   if the file actually doesn't exist (stat() fails or it wasn't dlpreopened)
   -> report `file not found'
   if it cannot be loaded (e.g. due to missing dependencies)
   -> report dlerror
    open question: which error should be reported if all dlloaders fail
    or if a specific module type can only be loaded by one of them, how report its dlerror?
   Also report dlerror() for dlclose and dlsym if available
 - Make sure that the dependency_libs of a dlpreopened module won't be loaded.
 
* Check whether the version of libtool.m4 is compatible with
ltconfig/ltmain.sh.  Meanwhile, the recommended approach for
developers using automake is to insert libtool.m4 in acinclude.m4.

* We could have an option to hardcode paths into libraries, as well as
binaries: `... -Wl,-soname -Wl,/tmp/libtest.so.0 ...'.  This is not
possible on all platforms, and is in part obviated by the ability of
linking libtool libraries specified with -lname, but it might still
be desirable.

* Lists of exported symbols should be stored in the pseudo library
so that the size of lt_preloaded_symbols can be reduced.

* Have some option to tell libtool not to include -L flags that point
into a certain tree in the dependence list of an installed library.
For example: -L-$top_builddir would let one link with libtool
libraries in sibling subdirectories within a project, using the -L
notation, without getting builddir pathnames ever mentioned in .la
files that get installed.

* Eric Lemings <[e-mail]> writes:
  Because of a growing number of config scripts for packages in GNOME 1.2
  (e.g. glib-config, xml-config, orbit-config. etc), development of GNOME
  2.0 spawned a separate tool called pkg-config that allows all packages
  to use one tool rather than several different scripts to query compile
  flags, link flags, and other configuration data.

  The functionality of pkg-config seems to me to have a lot of overlap
  with the goals of libtool.  I was wondering if anyone had considered
  adding an eighth mode to libtool that just queries the installed
  library for the same information that pkg-config provides.  Since
  most packages that use pkg-config also use libtool, I think this
  would be a good way to reduce maintainer and developer dependencies.


In the future:
**************

* The definitions for AC_LTDL_SHLIBEXT, AC_LTDL_SHLIBPATH and
AC_LTDL_SYSSEARCHPATH  should not rely on the _LT_AC_LTCONFIG_HACK
macro.  This involves moving the code which sets the variables
library_names_spec, shlibpath_var and sys_lib_dlsearch_path_spec from
into a separate macro, and AC_REQUIRING the newly extracted macro in the
respective ltdl.m4 macros.

* Godmar Back writes:
  libltdl uses such stdio functions as fopen, fgets, feof, fclose, and others.
  These functions are not async-signal-safe. While this does not make 
  libltdl unusable, it restricts its usefulness and puts an 
  unnecessary burden on the user.

  As a remedy, I'd recommend to replace those functions with functions
  that POSIX says are async-signal-safe, such as open, read, close.
  This will require you to handle interrupted system calls and implement
  fgets, but the former isn't hard and there's plenty of implementations
  out from which you can steal the latter.

  I believe relying on async-signal-safe functions to the greatest extent
  possible would greatly improve libltdl's ability to be embedded in and 
  used by other systems.

* Arrange that EXEEXT suffixes are stripped from wrapper script names
only when needed, and that a timestamp file or a wrapper program is
created with the EXEEXT suffix, so that `make' doesn't build it every
time.

* Figure out how to use data items in dlls with win32.
The difficult part is compiling each object which will be linked with an
import lib differently than if it will be linked with a static lib.  This will
almost definitely require that automake pass some hints about linkage in to
each object compilation line.

* [e-mail] writes
	all you need to do for mutually dependent
	.dll's is to create an implib from a .def file
so it appears that we might need to detect and handle mutual dependencies
specially on win32 =(O|

* If not cross-compiling, have the static flag test run the resulting
binary to make sure everything works.

* Implement full multi-language support.  Currently, this is only for
C++, but there are beginnings of this in the manual (Other Languages).
This includes writing libtool not to be so dependent on the compiler
used to configure it.

We especially need this for C++ linking, for which libtool currently
does not handle static constructors properly, even on operating
systems that support them.  ``Don't use static constructors'' is no
longer a satisfactory answer.

* Another form of convenience library is to have undocumented utility
libraries, where only the shared version is installed.

* We could use libtool object convenience libraries that resolve
symbols to be included in a libtool archive.  This would require some
sort of -whole-archive option, as well.

* Currently, convenience libraries (.al) are built from .lo objects,
except when --disable-shared.  When we can build both shared and
static libraries, we should probably create a .al out of .lo objects
and also a .a out of .o objects.  The .al would only be used to create
shared libraries, whereas the .a would be used for creating static
libraries and programs.  We could also explicitly support `empty'
convenience libraries, that behave as macros that expand to a set of
-Rs, -Ls and -ls switches.

* We should include tests with convenience libraries and reloadable
objects in the testsuite.

* Try to find a work-around for -[all-]static and libltdl on platforms
that will fail to find dlopening functions in this case.  Maybe
creating an alternate libltdl that provides only for dlpreopening, or
creating an additional static library to provide dummy implementations
of the functions that can't be linked statically.  This could hardly
be made completely transparent, though.

* Need to finalize the documentation, and give a specification of
`.la' files so that people can depend on their format.  This would be
a good thing to put before the maintainance notes.

* Filenames containing shell meta-characters are not properly handled
by libtool.  Compiling a file named "a;b.c", for example, fails.

* We could introduce a mechanism to allow for soname rewriting, to
ease multi-libc support.  Installers could specify a prefix, suffix or
sed command to modify the soname, and libtool would create the
corresponding link.  This would allow for rebuilding a library with
the same version number, but depending on different versions of libc,
for example.  In the future, we might even have an option to encode
the sonames of all dependencies of a library into its soname.

* The current implementation of libltdl in a subdirectory doesn't work
properly with AC_CONFIG_AUX_DIR using projects.

Things to think about:
**********************

* Maybe implement full support for other orthogonal library types
(libhello_g, libhello_p, 64 vs 32-bit ABI's, etc).  Make these types
configurable.

* Perhaps the iuse of libltdl could be made cleaner by allowing
registration of hook functions to call at various points.  This would
hopefully free the user from having to maintain a parallel module
list with user data.  This would likely involve being able to carry
additional per user module data in the lt_dlmodule structure -- perhaps
in the form of an associative array keyed by user name?